‘ p.15 [mum .‘ s‘kifl OVERDUE FINES: 25¢ per day per item RETUMI'G LIBRARY MATERIALS: Place in book return to remove charge from circulation records ECOLOGY OF PRATYLENCHUS PENETRANS ASSOCIATED WITH NAVY BEANS (PHASEOLUS VULGARIS L.) BY Alma Patricia Elliott A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Entomology 1980 ABSTRACT ECOLOGY OF PRATYLENCHUS PENETRANS ASSOCIATED WITH NAVY BEANS (PHASEOLUS VULGARIS L.) BY Alma P. Elliott A "holistic" approach was used to study the ecology of Pratylenchus penetrans associated with navy beans. Studies on the pest system included determination of the field distribution and incidence of Pratylenchus penetrans in Michigan bean fields. The pathogenicity of g. penetrans to navy bean cv Sanilac was evaluated and the susceptibility of dry bean varieties to g. penetrans was examined. The influence of environmental factors of temperature and moisture on the development of the pathogenic relationship between 3. penetrans and navy beans was studied. Effects of interacting components of mycorrhizae and kidney beans which are grown in rotation with navy beans were examined. The research findings indicated an aggregate-type field distribution of g. penetrans, and this expresses the need for careful design of experimental sampling Alma P. Elliott procedures and analyses of nematode data. Pratylenchus spp. was found in 68% of Michigan bean fields. A patho- genic relationship between 2. penetrans and navy bean cv Sanilac was observed. However, the degree of suscep- tibility of varieties to E. penetrans varied, and three tolerant varieties (Gratiot, Saginaw and Kentwood) were identified. The population dynamics of g. penetrans varied over two navy bean growing seasons. The pathogenic relationship between E. penetrans and navy beans was emphasized by adverse conditions of temperature, soil type and soil moisture. Reproduction of g. penetrans was reduced at 15 and 30 C, respectively and at high and low soil moisture levels corresponding to -5 and -1000 centibars, respectively. Optimum con- ditions for growth and development of g. penetrans were 25 C and a soil moisture level corresponding to a matrix potential of -50 centibars. These conditions were also optimum for plant growth in the absence of g. penetrans. Mycorrhizal associations with g. fasciculatus in- creased growth and yield of navy bean cv Sanilac. The detrimental effects of g. penetrans on navy beans were minimized in the presence of g. fasciculatus. The research data provided information which could be used Alma P. Elliott for development of management strategies for control of B. penetrans in dry bean production. ACKNOWLEDEGEMENTS The author would like to express deep thanks to all persons who contributed to the development and progress of the Ph.D program. Profound thanks and deep gratitude are due to the Chairman of the Guidance Commit- tee, Dr. G. W. Bird, for his ingenious asssistance and kind support throughout the program. Sincere appreciation and thanks are expressed to Dr. D. L. Haynes for his patience and perseverance in assisting the author with development of philosophical perspectives. Deep thanks are expressed to Dr. T. Edens for his kind support and assistance throughout the program. Sincere thanks are due to Dr. A. Smucker for his assistance with numerous questions and support throughout the program. Deep thanks are expressed to Dr. G. Safir for his willing assis- tance and support throughout the program. The author is grateful to the Chairman of the Department of Entomology, Dr. J. Bath, for his support and encouragement throughout the program. Sincere thanks are expressed to Mr. K. Dimiff for his assistance with data processing on the CDC 750. Thanks are due to Dr. R. Kunze for his assistance with research involving soil ii moisture. Special thanks are due to Mr. John Davenport for his assistance with field research. Sincere thanks are expressed to Ms. R. Hannewald and Ms. B. Wyse for their assistance in typing the dissertation. Sincere thanks and deep gratitude are expressed to Ms. Laura Meal for most competent and excellent input in typing and editing the final copy of the dissertation. Alma P. Elliott iii TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . . . . . LIST OF FIGURES O O O O O O O O O O O O C l O 0 INTRODUCT ION O O C O O O O O O O O O O 1.1 Agricultural Production Systems . . . . 1.2 Approach to the Study of Pest-crop ecosystems . . . . . . . . . . . . . 1.3 Nematode Problems in Agricultural Production . . . . . . . . . . . . . . 1.4 Statement of the Problem . . . . . . . 1.4.1 Approach to the study of the problem . . . . . . . . . . . . . . 1.4.2 Overall research objective . . . 1.4.3 Research outline . . . . . . . . 1.4.3.1 The pest system . . . . . . . . 1.4.3.2 Pest-crop interactions . . . . 1.4.3.2.1 Influence of environmental parameters of temperature and moisture . . . . . . . . . 1.4.4 Influence of interacting components 1.4.4.1 Mycorrhizae . . . . . . . . . . 1.4.4.2 Rotation crops - Kidney beans . 2.0 LITERATURE REVIEW . . . . . . . . . . . 2.1 Pratylenchus penetrans . . . . . . . . 2.1.1 Taxonomy . . . . . . . . . . . . . 2.1.2 Morphology . . . . . . . . . . . . 2.1.3 Distribution and host range . . . . 2.1.4 Life cycle . . . . . . . . . . . . 2.1.4.1 The primary cycle . . . . . . . iv Page xi xxii \I\I\I\IO\ 0000000 10 10 10 11 13 l4 l7 2.1.4.1.1 Inoculation . 2.1.4.1.2 Incubation . 2.1.4.1.3 Infection . . 2.1.4.2 Secondary cycles 2.1.5 Symptomatology . . . 2.1.6 Ecology . . . . . . . 2.2 2. 2. 2. 2. 2.3 2.1.6.1 2.1.6.2 2.1.6.3 2.1.6.4 2.1.6.5 Temperature . . . Soil nutrients . Soil moisture . . Interactions with Nematode-nematode fungi . . . . interactions Navy Beans (Phaseoulus vulgaris L) . . 2.1 Importance . . . . . 2.2 Marketing . . . . . . 2.3 Supply and price . . 2.4 Production factors affecting yield 2.2.4.1 2.2.4.2 2.2.4.3 2.2.4.4 2.2.4.5 2.2.4.6 Symbionts in Association with Navy Beans Environmental factors . . . . . Navy bean varieties . . . . . . Cultural practices Soil fertility factors . . . . Bean diseases . . Nematode diseases 2.3.1 Mycorrhizae . . . . . 3.0 EXPERIMENTAL . . . . . . 3.1 General procedures . . . 3.1.1 Soil samples . . . . 3.1.1.1 3.1.1.2 Field samples . . Greenhouse samples 3.1.2 Root samples . . . . Page 18 18 19 20 20 21 22 23 24 25 25 27 27 28 28 29 29 3O 30 32 33 35 36 36 42 42 42 42 42 42 3.1.2.1 Field samples . . . . . . . . . . . . 3.1.2.2 Greenhouse samples . . . . . . . . . 3.1.3 Nematode extraction . . . . . . . . . . . 3.1.3.1 3.1.3.2 Soil samples . . . . . . . . . . . . Root samples . . . . . . . . . . . . 3.1.4 Identificaticn and calculation of nematode population densities . . . . . . 3.1.5 Extraction of vesicular-arbuscular mycorrhizal spores from soil . . . . . . 3.1.6 Identification of vesicular-arbuscular mycorrhizae in root samples . . . . . . . 3.1.7 Converting time to accumulated degree days . . . . . . . . . . . . . . . 3.1.8 Plant growth analysis . . . . . . . . . . 3.1.9 Soil moisture characteristic curves . . . 3.2 Pest system . . . . . . . . . . . . . . . . . 3.2.1 Field distribution of Pratylenchus penetrans . . . . . . . . . . . . . . . . 3.2.1.1 methOd O O O O O I O O O O O O O O 0 3.2.2 Indcidence of Pratylenchus penetrans in dry bean fields of Michigan . . . . . . 3.2.2.1 Method . . . . . . . . . . . . . . . 3.2.3 Development of an experimental pOpula- tion of Pratylenchus penetrans . . . . . 3.2.3.1 methOd O O O O I O O O O O O O O O 0 3.2.4 Identification of the life cycle stages of Pratylenchus penetrans . . . . . . . . 3.2.4.1 Method . . . . . . . . . . . . . . . 3.2.5 Results . . . . . . . . . . . . . . . . . 3.2.5.1 3.2.5.2 3.2.5.3 Field distribution of Pratylenchus penetrans . . . . . . . . . . . . . . Incidence of P. penetrans in dry bean fields in Michigan . . . . . . . . . Development of an experimental pOpulation of P. penetrans . . . . . vi Page 42 42 43 43 43 44 44 45 45 46 47 49 49 49 52 52 55 55 57 57 59 59 77 83 3.2.5.4 Identification of the life cycle stages of P. penetrans . 3.2.6 Discussion . . . . . . . . . . 3.3 Pest-crop Interactions . . . . . . 3.3.1 Pathogenicity . . . . . . . . . 3.3.1.1 Method . . . . . . . . . . 3.3.2 Susceptibility of six navy bean to Pratylenchus penetrans . . . 3.3.2.1 Method . . . . . . . . . . 3.3.3 Responses of Sanilac navy beans varieties to infec- tion with different initial pOpulation densities of Pratylenchus penetrans . 3.3.3.1 Method . . . . . . . . . . 3.3.4 Results . . . . . . . . . . . . 3.3.4.1 Pathogenicity . . . . . . . 3.3.4.2 Susceptibility of six navy bean varie- ties to Pratylenchus penetrans 3.3.4.3 Responses of Sanilac navy beans to infection with different densities of Pratylenchus penetrans . . 3.3.5 Discussion . . . . . . . . . . 3.4 Influence of Environmental Parameters of Temperature and Moisture . . . . . 3.4.1 Influence of temperature . . . 3.4.1.1 Effect of different temperatures and different initial densities of Praty- lenchus penetrans on growth and yield of navy beans and on final population densities of Pratylenchus penetrans . 3.4.1.1.1 Method . . . . . . . . 3.4.1.2 Interactions of temperature and P. penetrans associated with navy beans over the growth period . . 3.4.1.2.1 Method . . . . . . . . 3.4.1.3 Results . . . . . . . . . . vii Page 91 96 109 109 109 110 110 111 112 113 113 119 131 169 176 176 176 176 178 178 179 Page 3.4.1.3.1 Effect of different temperatures and different initial densities of P. penetrans on growth and yield of navy beans and on final population densities of P. penetrans . . . . . . . . . . . 179 3.4.1.3.2 Interactions of temperature and and P. penetrans associated with navy beans over the growth period . . . . . . . . . . . . . . 188 3.4.1.4 Discussion . . . . . . . . . . . . . . 193 3.4.2 Influence of soil moisture . . . . . . . . 198 3.4.2.1 Development of soil moisture charac- teristic curves for three soil types . 198 3.4.2.1.1 Method . . . . . . . . . . . . . . 198 3.4.2.2 Interactions of soil type, soil mois- ture and P. penetrans associated with navy beans . . . . . . . . . . . . . . 199 3.4.2.2.1 Method . . . . . . . . . . . . . . 199 3.4.2.3 Effect of interactions of soil type, soil moisture and initial population densities of P. penetrans on growth and yield of navy beans and on popu- lation densities of P. penetrans . . . 202 3.4.2.3.1 Method . . . . . . . . . . . . . . 202 3.4.2.4 Results . . . . . . . . . . . . . . . . 203 3.4.2.4.1 Development of soil moisture characteristic curves for three soil types . . . . . . . . . . . . 203 3.4.2.4.2 Interactions of soil type, soil moisture and P. penetrans associa- ted with navy beans . . . . . . . . 204 3.4.2.4.3 Effect of interactions of soil type, soil moisture and initial population densities of g. pene- trans on growth and yield of navy beans and on population densities of P. penetrans . . . . . . . . . . 220 3.4.3 Discussion . . . . . . . . . . . . . . . . 226 viii 3.5 Interactions of P. penetrans and Mycorrhizae . 3.5.1 Effect of initial population densities of Glomus fasciculatus on growth and yield of navy beans . . . . . . . . . . . . . . 3.5.1.1 Method . . . . . . . . . . . . . . . . 3.5.2 Interactions of P. penetrans and g. fas- ciculatus and effect on growth and yield of navy beans . . . . . . . . . . . . . . 3.5.2.1 Method . . . . . . . . . . . . . . . . 3.5.3 Results . . . . . . . . . . . . . . . . . . 3.5.3.1 Effect of initial population densities of Glomus fasciculatus on growth and yield of navy beans . . . . . . . . . 3.5.3.2 Interactions of g. penetrans and g. fasciculatus and effect on growth and yield of navy beans . . . . . . . 3.5.4 Discussion . . . . . . . . . . . . . . . . 3.6 Rotation Crops - Kidney Beans . . . . . . . . . 3.6.1 Susceptibility and control of g. penetrans associated with five dry bean varieties . . 3.6.1.1 Method . . . . . . . . . . . . . . . . 3.6.2 Results . . . . . . . . . . . . . . . . . . 3.6.2.1 Susceptibility and control of P. penetrans associated with five dry bean varieties . . . . . . . . . . 3.6.3 Discussion . . . . . . . . . . . . . . . . 3.7 Comparison of Population Dynamics of P. pene- trans Associated with Navy Beans Over Two Growing Seasons . . . . . . . . . . . . . . . . 3.7.1 Population dynamics and control of P. penetrans associated with navy beans in 1978 O O O O O O O O O O I O I O O O O 0 3.7.1.1 Method . . . . . . . . . . . . . . . 3.7.2 Population dynamics and control of P. penetrans associated with navy beans in 1979 . . . . . . . . . . . . . . . . . . ix Page 233 233 233 234 234 235 235 238 251 256 256 256 256 256 257 259 259 259 260 Page 3.7.2.1 Method . . . . . . . . . . . . . . . . 260 3.7.3 Results . . . . . . . . . . . . . . . . . . 261 3.7.3.1 Population dynamics and control of P. penetrans associated with navy beans in 1978 . . . . . . . . . . 261 3.7.3.2 Population dynamics and control of P. penetrans associated with navy beans in 1979 . . . . . . . . . . . . . 264 3.7.4 Discussion . . . . . . . . . . . . . . . . 266 4.0 GENERAL DISCUSSION . . . . . . . . . . . . . . 268 An Overview of the Research Findings . . . . . 268 4.2 A Conceptual Model of the P. penetrans Navy Bean System Based on Research Findings . . 268 5.0 SUMMARY AND CONCLUSIONS . . . . . . . . . . . . 271 6.0 APPENDIX A . . . . . . . . . . . . . . . . . . 275 7.0 BIBLIOGRAPHY . . . . . . . . . . . . . . . . . 336 LIST OF TABLES Page Analysis of field distribution of Pratylenchus penetrans . . . . . . . . 60 Occurrence and densities of Pratylenchus spp. (root lesion nematodes) recovered from 80 dry bean fields in Michigan . . . 82 Occurrence of plant-parasitic nematodes in relation to soil type and bean variety . . . . . . . . . . . . . . . . . 84 Pratylenchus spp. (root-lesion nematodes) associated with navy bean and colored beans in Bay and Montcalm counties . . . . 88 Occurrence of plant-parasitic nematodes recovered from 80 dry bean fields in Michigan in 1978 . . . . . . . . . . . . . 89 Occurrence and population densities of Tylenchorhynchus (stunt nematodes) recovered from 80 Michigan dry bean fields in 1978 . . . . . . . . . . . . . . 90 Morphometric characters of the life cycle stages of Pratylenchus penetrans associated with navy beans . . . . . . . 94 Morphometric characters of Pratylenchus penetrans . . . . . . . . . . . . . . . . 95 Allometric characters of the life cycle stages of Pratylenchus penetrans associated with navy beans . . . . . . . . 97 Differences in allometric characters of Pratylenchus penetrans life cycle stages . . . . . . . . . . . . . . . . 98 Key to the life cycle stages of Pratylenchus penetrans . . . . . . . . . . 108 xi 3.13A 3.13B 3.13C A1 A2 A3 A4-1 A4-2 A5 LIST OF TABLES (continued) Influence of temperature on popula- tion cohort of P. penetrans associated with navy beans . . . . . . . . . . . . . Volumetric soil moisture content as re- lated to matrix potential . . . . . . . . Mechanical composition of soils . . . . . Percent soil moisture associated with different matrix potentials . . . . . . . Dynamics of the population cohort of P.penetrans associated with navy beans .. The effect of Pratylenchus penetrans on height of six dry bean varieites . . . The effect of Pratylenchus penetrans on root weight of six dry bean varieties . . . . . . . . . . . . . . . . The effect of Pratylenchus penetrans on leaf area of six dry bean varieties . . . . . . . . . . . . . . . . Influence of initial population density of P. penetrans on root population dynamics of P. penetrans associated with navy beans . . . . . . . . . . . . . Influence of initial population density of P. penetrans on soil population dynamics of P. penetrans associated with navy beans . . . . . . . . . . . . . . . Influence of intial population densi- ties of P. penetrans on total (root + soil) population dynamics of P. penetrans associated with navy beans . . . . . . . Effect of different initial densities of P. penetrans on weight of navy bean roots over the growth period . . . . . . . . . xii Page 182 200 200 200 26 275 276 277 278 278 279 279 Table A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 A16 LIST OF TABLES (continued) Effect of different intital densities of P.penetrans on leaf area of navy beans over the growth period . . . . . . . . . Effect of different initial densities of P. penetrans on shoot fresh weight of navy beans over the growth period . . . . Effect of different initial densities of P. penetrans on dry weight of navy bean shoot system over the growth period.. Interactions of initial density of P. penetrans and temperature on final foot densities of p. penetrans . . . . . . Interactions of initial density of P. penetrans and temperature on final soil population densities of P. penetrans . . . . . . . . . . . . . . . . Interactions of initial density of P. penetrans and temperature on final total population densities of P. penetrans . . . . . . . . . . . . Effect of P. penetrans on height of navy bean plants at different temp- eratures O O O O O O O O O O O O O O Effect of P. penetrans on weight of navy bean roots at different temp- eratures O O O O C O O I O O O I O O O Effect of P. penetrans on dry weight of navy bean shoot system at four different temperatures . . . . . . . . . Effect of P. penetrans on yield of navy beans at different temperatures . . Effect of temperature on total population densities (root & soil) of p. penetrans associated with navy beans over the growth period . . . . . . . . . . . . . xiii Page 280 280 281 282 .282 283 283 284 284 285 286 Table A17 A18 A19 A20 A21 A22 A23 A24 A25 A26-1 A26-2 A26-3 LIST OF TABLES (continued) Effect of temperature on root densi- ties of P. penetrans associated with navy beans over the growth period . . . . Effect of temperature on soil densi- ties of P. penetrans associated with navy beans over the growth period . . . Influence of temperature and P. penetrans on shoot dry weight of navy beans over the growth period . . . . . . Effect of temperature and P. penetrans on root area of navy beans . . . . . . . Effect of temperature and P. penetrans on root weight of navy beans over the growth period . . . . . . . . . . . Effect of temperature and P. penetrans on height of navy bean plants over the growth period . . . . . . . . . . . Effect of temperature and P. penetrans on shoot fresh weight of navy beans over the growth period . . . . . . . . Effect of temperature and P. penetrans on length of navy bean roots over the growth period . . . . . . . . . . . Effect of temperature and P. penetrans on leaf area of navy beans over the growth period . . . . . . . . . . . . . Effect of soil moisture on final root populations of Pratylenchus penetrans associated with navy beans . . . . . . . Analysis of variance . . . . . . . . . . Interactions of soiltype and soil mois- ture on final root densities of P. pene- trans associated with navy beans . . . . xiv Page 286 287 287 288 288 289 289 290 290 291 291 292 Table A26-4 A26-5 A27-l A27-2 A27-3 A27-4 A27-5 A28 A29-1 A29-2 A29-3 A29-4 A30-1 LIST OF TABLES (continued) Interactions of soil type and initial density od P. penetrans . . . Interactions of soil moisture and initial density of P. penetrans . Effect of soil moisture and P. penetrans on final soil population densities of Pratylencus penetrans associated with navy beans Analysis of variance . Interactions of soil type and initial density of P. penetrans on final soil densities of P. penetrans associated with navy beans . . . . Interactions of soil type and soil moisture . . . . . Interactions of soil moisture and initial density of P. penetrans Effect of soil moisture on final total (root + soil) densities of P. penetrans associated wirh navy beans Effect of P. penetrans on length of navy bean roots grown at six different soil water potentials . Analysis of variance . Interactions of soil moisture and initial density of P. penetrans on length of navy bean roots . Interactions of soil type and soil moisture . . . . . . . Effect of P. penetrans on dry weight of navy bean plants grown at six different soil water potentials . XV Page 292 292 293 293 294 294 294 295 296 296 297 297 298 Table A30-2 A30-3 A30-4 A30-5 A31-1 A31-2 A31-3 A3l-4 A31-5 A32-1 A32-2 A32-3 A32-4 A32-5 LIST OF TABLES (continued) Analysis of variance . Interactions of soil type and soil moisture on shoot dry weight of navy beans Interactions of soil moisture and initial density of P. penetrans . Interactions of soil type and initial density of P. penetrans . Effect of P. penetrans on height of navy bean plants grown at six different moisture levels Anlaysis of variance . Interactions of initial density soil moisture on height of navy bean plants . . Interactions of soil type and initial density of P.penetrans . Interactions of soil mositure and soil type . Effect of P.penetrans on root area of navy bean plants grown at six differ- ent water potentials Analysis of variance . Interactions of initial density of P. penetrans and soil moisture on area 5f navy bean roots . Interactions of soil type and initial density of P. penetrans . Interactions of soil moisture and soil type . xvi and Page 298 298 298 298 300 300 301 301 301 302 302 303 303 303 Table A33-1 A33-2 A33-3 A33-4 A33-5 A34-1 A34-2 A34-3 A34-4 A34-5 A35-1 LIST OF TABLES (continued) Effect of P. penetrans on yield of} dry beans grown at six different matrix potentials . . . . . . . . . . . Analysis of variance . . . . . . . . . Interactions of soil type and soil moisture on yield of navy beans . . . Interactions of soil moisture and initial density of P. penetrans . . . . Interactions of soil type and initial density of P. penetrans . . . . . . . . Effect of interactions of soil water potential , soil type and initial population densities of P. penetrans on root population densities of P. penetrans over time . . . . . . . . . Interactions of soil type , soil mois- ture and initial density of P. penetrans on root population densities—of P. penetrans at 1056 DD 10 C . Analysis of variance . . . . . . . . . . . . . . Interactions of soil type and soil mois— ture on final root densities of P. penetrans associated with navy beans . Interactions of soil type and initial density of P. penetrans . . . . . . . . Interactions of soil moisture and initial density of P. penetrans . . . . Effect of interaction of soil water potential, soil type and different initial population densities of P. penetrans on soil population densi- Page 304 304 305 305 305 306 307 .308 308 308 ties of P. penetrans over time . . . . . . 309 xvii Table A35-2 A36-1 A36-2 A36-3 A36-4 A36-5 A37-1 A37-2 A37-3 A37-4 A37-5 A37-6 A37-7 A37-8 LIST OF TABLES (continued) Interactions of soil moisture , soil type and P. penetrans on soil densities of P.penetrans at 1056 DD 10 C . Analysis of variance . . . . . . . . Effect of soil moisture ,soil type and initial population densities of Praty- lenchus penetrans on final population densities of P. penetrans . . . . . . Analysis of variance . . . . . . . . Interactions of soil type and soil moisture on final population densitie of P. penetrans . . . . . . . . . . . Interactions of soil moisture and initial population density of P.penetrans . . . . . . . . . . . . . S Interactions of initial population den— sity of P. penetrans and soil type . Effect of interactions of soil water potential , soil type and different initial population densities of P. penetrans on navy bean root weight over time . . . . . . . . . . . . . . Analysis of variance . . . . . . . . Analysis of variance . . . . . . . . Analysis of variance . . . . . . . . Analysis of variance . . . . . . . . Interactions of initial density and soil moisture on weight of navy bean roots 0 O O O O O O O O O O O O O O Interactions of soil type and initial density of P. penetrans . . . . . . . Interactions of soil mositure and soil type . . . . . . . . . . . .. . xviii Page 310 311 311 312 312 312 313 314 314 315 315 316 316 316 Table A38-1 A38-2 A38-3 A38-4 A38-5 A38-6 A38-7 A38-8 A39-1 A39-2 A39-3 A39-4 A39-5 A40-1 A40-2 LIST OF TABLES (continued) Effect of interactions of soil water potential , soil type and different initial population densities of P. penetrans on navy bean shoot dry weight over time . . . . . . . . . Analysis of variance . . . . . . . Analysis of variance . . . . . . . . Analysis of variance . . . . . . . . Analysis of variance . . . . . . . . Interactions of soil moisture and P.penetrans on shoot dry weight of navy beans . . . . . . . . . . . . . Interactions of soil type and soil 1110151111168 0 o o ‘ o o ‘ o ‘‘‘‘‘‘ o o o o Interactions of soil type and initial density of P. penetrans . . Effect of interactions of soil water potential, soil type and different initial population densities of P. penetrans on height of navy bean Ever tImes . . . . . . . . . . . . . Analysis of variance . . . . . . . . Analysis of variance . . . . . . . . Analysis of variance . . . . . . . . Analysis of variance . . . . . . . Effet of soil type, soil moisture and initial density of Pratylenchus penetrans on yield of navy beans . . Analysis of variance . . . . . . . . xix Page 317 318 318 319 319 320 320 320 321 322 322 323 323 324 324 Table A40-3 A40-4 A40-5 A41 A42 A43 A44 A45 A46 A47 A48 A49 LIST OF TABLES (continued) Effect of interactions of soil type and P. penetrans on yield of navy beans . . . . . . . . . . . . . . . Interactions of soil moisture and initial density of P. penetrans . . . . . Interactions of soil type and soil moisture . . . . . . . . . . . . . . . Effect of different densities of Glomus fasciculatus on growth and yield of navy beans . . . . . . . . . . . . . . . Effect of different densities of g. fasciculatus on area , weight and length of navy bean roots and on mycorrhizal root infection and number of spores . . . Percent infection of root systems of navy beans by g. fasciculatus . . . . Spore density of g. fasciculatus associ- ated with navy beans . . . . . . . . . . Effect of interactions of P. penetrans and G. fasciculatus on fresh weight of navy bean plants . . . . . . . . . . . Effect of interactions of P. penetrans and G. fasciculatus on shoot dry weight of navy beans . . . . . . . . . . Effect of interactions of P. penetrans and g. fasciculatus on leaf area of navy bean plants . . . . . . . . . . . . Effect of interactions of P. penetrans and G. fasciculatus on height of navy bean plants. . . . . . . . . . . . . . . Effect of interactions of P. penetrans and g. fasciculatus on weight of navy bean roots . . . . . . . . . . . . . . . XX Page 325 325 325 326 .327 328 328 329 329 330 330 331 Table A50 A51 A52 A53 A54 LIST OF TABLES (continued) Effect of interactions and G. fasciculatus on bean roots . . . . . . Effect of interactions and G. fasciculatus on bean roots . . . . . . Susceptibility of five to P. penetrans and control of P penetrans with an input of aldicarb (Temik 15G) . . . . . Population dynamics and control of Pratylenchus penetrans with navy beans (1978) Population dynamics and control of P.penetrans associated with navy beans 71979) . . . . . . . xxi Page of P.penetrans area of navy . . . . . . . . . . 331 of P. penetrans length of navy . . . . . . . . . . 332 dry bean varieites . . . . . . . . 333 associated . . . . . . . . . 334 . . . . . . . . 335 LIST OF FIGURES Figure Page 2.1 Life cycle of Pratylenchus penetrans ...... 16 3.1 Plot plan for the study of the field distribution of Pratylenchus penetrans.... 50 3.2 Sampling scheme for subplots .............. 51 3.3 Plot plan for the study of the field distribution of Pratylenchus penetrans in the ploughed and unploughed sections of the field...... ..... ........ ........... 53 3.4 Plot plan for the randomized block designs ................................... 54 3.5 Counties included in a survey of P. penetrans in dry bean fields in Michigan......... ......................... 56 3.6 Distribution of P. penetrans in the field .................. . .................. 65 3.7 Distribution of P. penetrans in subplots... 66 3.8 Distribtuion of P. penetrans from samples consisting of one soil core... ..... 67 3.9 Soil distribution of P. penetrans from the section of the fiEld covered with rye.. 68 3.10 Soil distribution of P. penetrans in subplots from the section of the field covered with rye ........ . .................. 69 3.11 Soil distribution of P. penetrans from samples consisting of one soil core from the section of field covered with rye ...... 70 3.12 Root distribution of P. penetrans in the section of the field covered with rye...... 71 xxii 3.23 LIST OF FIGURES (continued) Page Root distribution of P. penetrans in subplots from the section of the field covered with rye............ ............. 72 Root distribution of P. penetrans from samples consisting of one core from the section of the field covered with rye.... 73 Distribution of P. penetrans (soil + root) in the section of the field covered with rye.....COCOOOOO ...... .0. ........ 00...... 74 Distribution of P. penetrans (root + soil) in subplots from the section of the field covered with rye........ .......... .. ..... 75 Distribution of P. penetrans (root + soil) from samples consisting of one core from the section of the field covered with rye................................ ....... 76 Distribution of P. penetrans in the ploughed section of the field....... ..... . 78 Distribution of P. penetrans in subplots in the ploughed section of the field...... 79 Distribution of P. penetrans from samples consisting of one soil core in the ploughed section of the field....... ...... 80 Distribution of P. penetrans in random— ized block design plots......... .......... 81 Total soil and root population densities of Pratylenchus penetrans associated with navy beans exposed to an initial density of one female and one male P. penetrans.... 92 Morphometric characters and biomass of life cycle stages of Pratylenchus penetrans ..... 93 xxiii Figure 3.27 3.28 3.29 3.31 3.32 LIST OF FIGURES (continued) Page Influence of initial soil population densities of P. penetrans on final soil population densities (A & B), and final root population densities (C & D) of P. penetrans associated with navy Beans...... ......... ... ..... ... ........... 114 Influence of different initial population densities of P. penetrans on leaf area (A) and height (B) of navy bean plants ........ 116 Effect of different initial population densities of P. penetrans on shoot fresh weight (A), shoot dry weight (B), root weight (C),and root length (D) of navy beans...... .......... .. .............. 117 Effect of different initial population densities of P. penetrans on navy bean yield............... ...... ... ........ 118 Population dynamics of P. penetrans associated with six navy bean varieties... 120 Influence of P. penetrans on height of six navy bean varieites over the growth period ...... . ...................... 121 Influence of P. penetrans on root weight of six navy bean varieties over the growth period............. ................ 124 Effect of P. penetrans on yield of six navy bean varieties............... ........ 127 Effect of P. penetrans on relative growth rate of six navy bean varieties over the growth periOd.. ....... ......OOOOOOOOOOOOOO 128 Relationship between total (Root + soil) final population densities of P. penetrans and initial soil population densities of P. penetrans............................... 132 xxiv Figure 3.34 3.37 3.38 3.40 3.41 3.42 3.43 3.44 LIST OF FIGURES (continued) Population dynamics of P. penetrans associated with navy beans exposed to an initial density of 320 P. penetrans per 100 cm3 soil ......................... Root-lesions produced by P. penetrans on navy bean roots ....................... Comparison of a noninfected and a P. penetrans infected navy bean root system. .................................. Relationships between navy bean plant height and initial soil population density of P. penetrans at different periods of growth ........................ Relationship between height of navy bean plants and initial population denSity of P. penetrans at different growth periods.. Effect of P. penetrans on height of navy bean plants over the growth period ........ Effect of P. penetrans on heights of navy bean plants over the growth period... Effect of different initial population densities of P. penetrans on root area of navy bean plants ....................... Relationship between root area of navy bean plants and the log of initial density of P. penetrans at 688 DD 10 C ........... Comparison of linear regression functions and a second degree polynomial function for the relationship between root area of navy bean plants and accumulated degree days.. ............... . ..... . ........... ... Influence of different initial population densities of P. penetrans on root area of navy bean plants over the growth period... XXV Page 134 135 137 140 142 143 145 147 149 151 152 Figure 3.45 3.47 3.48 3.49 3.50 3.52 3.54 LIST OF FIGURES (continued) Influence of initial population densities of P. penetrans on root area of navy bean plants over the growth period.... ...... ... Effect of different initial popualtion densities of P. penetrans on yield of navy beans .............................. Relationship between yield of navy beans and log of initial population density of P. penetrans Effect of P. penetrans on growth of navy beans .......... . .......... . .............. Comparison of growth of navy bean plants in the absence of P. penetrans and in the presence of an initial density of 320 E; penetrans per 100 cm soil ........... Influence of different initial population densities of P. penetrans on relative growth rate of navy bean plants over the growth period .. ..... . ............... Influence of different initial population densities of P. penetrans on relative growth rate of navy beans over the growth period ........... ........ ... ..... Influence of temperature on population densities of P. penetrans associated with navy beans 0 o o o ........... o O 0000000000000 Influence of temperature on final total (root + soil) densities of P. penetrans associated with navy bean plants exposed to different initial population densities of P. penetrans ............... Effect of temperature on height (A) and shoot dry weight (B) of navy bean plants exposed to different initial densities of P. penetrans ........... ...... ......... xxvi Page 154 156 157 159 161 163 165 180 181 Figure 3.55 3.57 3.58 3.61 3.62 3.63 3.64 LIST OF FIGURES (continued) Page Effect of temperature on root weight of navy bean plants exposed to different initial densities of P. penetrans ... ..... 186 Effect of temperature on yield of navy bean plants exposed to different initial densities of P. penetrans . ............... 187 Influence of temperature on population dynamics of P. penetrans over the growth period of navy beans ... .................. 189 Effect of P. penetrans on shoot dry weight of navy beans over the growth period at four temperatures ..... ..... .............. 190 Effect of temperature on shoot dry weight of noninfected and P. penetrans infected navy bean plants over the growth period .. 191 Effect of P. penetrans on root area of bean plants over the growth period at four temperatures 00............OOOOOOOOOOIO0.0 192 Influence of temperature on yield of noninfected and P. penetrans infected navy beans .................... ........... 194 Volumetric soil moisture content associa- ted with three soil types at different matrix potentials ........... ............. 205 Influence of interactions of soil type and soil moisture (A), soil type and initial density of P. penetrans (B) and soil moisture and initial density of P. penetrans (C) on final root population densities of P. penetrans ..... ...... .... 206 Influence of interactions of soil type and initial density of P. penetrans (A), soil type and soil moistfire (B), and soil mois- ture and initial density of P. penetrans (C) on final soil population densities of P. penetrans ......................... 207 xxvii Figure 3.65 3.66 3.68 3.69 3.71 LIST OF FIGURES (continued) Influence of soil moisture on total population densities (root + soil) of P. penetrans associated with navy beans in three soil types ............. Influence of interactions of soil moisture and initial density of P. penetrans (A), and soil type and soil moisture (B) on root length of navy beans .............. ...... .. ...... ..... Influence of interactions of soil type and soil moisture (A), soil moisture and initial density of P. penetrans (B) and soil type- and initial density of P. penetrans (C) on shoot dry weight of navy beans .......... ..... ..... ...... Influence of interactions of soil moisture and initial density of P. penetrans (A), soil type and initial density of P. penetrans (B) and soil moisture and soil type (C) on heights of navy bean plants ............. ....... Influence of interactions of soil moisture and initial density of P. penetrans (A), soil type and initial density of P. penetrans (B) and soil moisture and soil type (C) on root area of navy bean plants ........... ........ Influence of interactions of soil mois- ture and soil type (A), soil moisture and initial density of P. penetrans (B) and soil type and initial density of P. penetrans (C) on yield of navy beans ........................ ..... .... Influence of soil moisture expressed as matrix potential on yield of noninfec- ted and P. penetrans infected navy beans grown 1n three soil types ....... xxviii Page 209 210 211 213 214 215 216 Figure 3.72 3.74 3.76 LIST OF FIGURES (continued) Page Influence of interactions of soil mois— ture and soil type (A), soil type and initial density of P. penetrans (B), and soil moisture and initial density of P. penetrans (C) on root population densities of P. penetrans at 1056 DD 10C.. 221 Influence of interactions of soil type and soil moisture (A), soil moisture and initial density of P. penetrans (B) and soil type and initial density of P. penetrans (C) on final total densities (root + soil) of P. penetrans associated with navy beans 7.... ......... 222 Influence of interactions of soil moisture and initial density of P. penetrans (A), initial density of P. penetrans and soil type (B) and soil moisture and soil type (C) on root weight of navy beans plants at 1746 DD 10C .............. ........... 224 Influence of interactions of soil moisture and initial density of P. penetrans (A), soil type and soil mois~ ture (B) and soil type and initial density of P. penetrans (C) on shoot dry weight of navy bean plants at 1056 DD 10 C ........ ....... . ...... .... ....... 225 Influence of interactions of soil type and initial density of P. penetrans (A) soil moisture and initial density of P. penetrans (B) and soil type and soil moisture (C) on yield of navy beans ...... 227 Relationship between percent vesicular- arbuscular mycorrhizal root infection of navy beans and log of initial spore density of G. fasciculatus .............. 236 xxix Figure 3.78 3.83 3.84 LIST OF FIGURES (continued) Effect of G. fasciculatus on shoot dry weight (A) —and leaf area (B) of navy beans ............................. ..... Effect of G. fasciculatus on root area (A) and root weight (B) of navy bean plants ................. ........ ... ..... Effect of G. fasciculatus on height of navy bean plants ....................... Effect of G. fasciculatus on yield of navy beans ...................... ....... Influence of G. fasciculatus and G. fasciculatEs plus P. penetrans on development of vesiCular-arbuscular mycorrhizal infection in navy bean roots (A) and on spore densities of G. fasciculatus (B) over the growth period ........... ..... ................. Population dynamics of P. penetrans associated with navy beans exposed to P. penetrans and P. penetrans plus G. fasciculatus respectively ............. Influence of P. penetrans, G. fasciculatus and P. penetrans plus G. fasciculatus on root area of navy bean plants over the growth period ...................... Relationship between root area and degree days of noninfected plants and navy bean plants infected with P. penetrans (A), G. fasciculatus (B) and p. penetrans plus G. fasciculatus (C) ............... Influence of P. penetrans, G. fascicu- latus and P. penetrans plus G. fasc1cu- latus on leaf area ratio of navy bean plants over the growth period ........... XXX Page 239 240 241 242 243 246 248 249 252 Figure 3.87 3.88 LIST OF FIGURES (continued) Influence of P; penetrans, G. fascicu- latus and P. penetrans plus G. fascicu- latus on yield of navy beans—.... ........ Population dynamics of P. penetrans (A) and control of P. penetrans with an input of alidcarb for control of P. penetrans associated with five dry bean varieties ........ .................. Population dynamics of P. penetrans associated with navy beans in 1978 and 1979 .......................... ......... . Components of the P. penetrans — navy bean ecosystem. ..... .................... xxxi Page 253 258 262 269 1.0 INTRODUCTION 1.1 Agricultural Production Systems Agricultural production systems represent vital linkages in the complex structual components of the world. The output of these systems is a function of natural and synthetic inputs such as climate, soil factors, fertilizers, plant varieties, pest and pest control inputs. Optimum production and economic returns from agricultural production systems are obtained through effective manage- ment of these variables. The output and economic returns of agricultural production systems can be significantly reduced by the detrimental effects of pests, and therefore pest manage- ment is a significant component. In many crop production systems pest control involves a single management factor effected through the use of pesticides. The continual use of pesticides, however, may lead to further development of the deleterious side effects of a "pesticide syndrome" (van den Bosh 25.21- 1971). The beneficial effects of pesticides cannot be discounted. However emphasis must be placed on the development of integrated methods (cultural, biological and chemical) for management of pesusin crop production systems. The concept of pest management defined as the coordination and implementation of pest control strategies that will result in favorable economic, ecologic and sociologic consequences (Bird, 1979) must be adopted to achieve optimum economic returns from crop production systems. The concept of integrated pest management is recognized and practiced by a significant number of farmers in the context of "farming practices". The application of this concept in modern-day agricultural systems has however been less than desired. This is related to the immediate economic gains which have resulted from the use of pesticides. Lack of understanding of the pest-crop ecosystem has also impeded the developement and implementation of integrated methods of pest control. The use of large monocultures in agricultural systems, the resulting decrease in species diversity, and the development of pest resistance to pesticides has resulted in increasing pest problems in crop production. These factors together with the awareness of the problem of depleting energy reserves has lead to an interdisciplinary movement to make integrated pest management a reality. New approaches to implementation of pest management are essen- tial for greater success. Implementation techniques, and applications of the concept have been addressed by several researchers (Stern g5_al. 1959; Haynes g; ai. 1973; OrishChenko 1974; Waters and Ewing, 1974; Tummala, 1974; Shoemaker, 1974; Polyakov, 1974; Haynes and Tummala, 1974; Croft e3 31. 1976; Harsh, 1977; Haynes and Tummala, 1978; Ferris, 1976). 1.2 Approach to the Study of Pest-crop Ecosystems In the past the "reductionist" approach was adopted in conducting studies on pest—crop interactions, in attempts to achieve pest control. This involved a concentration of effort on one pest and one crop. Pest- crop interactions, however are influenced by other com- ponents of the ecosystem. To truly determine and under- stand the nature of pest-crop interactions it is necessary to adopt a "holistic" approach to the study of pest-crop ecosystems. This is achieved through studies on the separate components of the pest-crop system and also through studies on the interdependence of each component .of the system. The principles of a "holistic" approach are based on the separation of the pest-crop system in to components of (l) the object of control (the pest) (2) the associated crop (3) other interacting components of the system. Because of the complex nature of ecosystems it is almost impossible to examine all possible inter— actions of the components. Studies are generally limited to first, second and third order interactions (Tummala and Haynes, 1979). Moreover, the components of the system can be divided into controllable factors such as plant variety, soil type and uncontrollable factors such as temperature, moisture and humidity. The number of con- trolled and uncontrolled factors involved in any study can be varied. 1.3 Nematode Problems in Agricultural Production Plant parasitic nematodes are pests which function by detrimentally affecting the physiological mechanisms of plants. Growth is usually retarded with consequent reduction in yield and economic returns. The development of effective feasible nematode control practices could aid in increasing output and economic returns from agri- cultural production systems. The development of these control practices will be influenced by the nature of the pest-crop system, natural resources and socio-economic conditions. Moreover, projections of future conditions should be considered in developing control methods, as practices developed to suit prevailing conditions could become obselete in the future due to changes in various aspects of the pest-crop system, and socioeconomic condi- tions. In the light of the diminishing natural energy resource, the development of low energy control inputs must be considered. This requires a decrease in the use of high energy nematicide inputs, and the develop— ment of an integrated nematode control approach which em- braces well-balanced use of multifactor control strategies such as nematode resistant varieties, crop rotation, op- timum planting dates, biological and chemical control. The development and implementation of this integrated control concept, however, requires a sound understanding of the functioning of the nematode-crop systems. This understanding can only be achieved through appropriate research on pest-crop ecosystems. 1.4 Statement of the Problem Root-lesion nematodes Pratylenchus spp. are common in many crop production systems in Michigan. Pratylenchus penetrans is the most predominant species. It is a patho- gen of many field crops such as potatoes, corn, soybeans, oats and wheat. Dry beans are commonly grown in rotation with many of these crops, and the presence of P. penetrans in dry bean roots has been reported (Bird, 1977). The nature of the relationship between this nematode pest and dry beans has not previously been established. In order to develop effective control strategies for management of this nematode pest it is necessary to study the ecology of P. penetrans associated with dry beans. 1.4.1 Approach to the study of the problem A primary prerequisite for development of optimum control practices is an understanding of the behavior of the pest-crop ecosystem. To determine the relationships which govern the behavior of the P. penetrans-navy bean system, a holistic approach was adopted whereby the pest- crop system was separated into the following components: (1) the object of control - the pest, P. penetrans (2) the associated crop - Phaseolus vulgaris (3) other interacting components (mycorrhizae, rotation crops, bacteria and fungi). Scientific experimental procedures were used in this investigation to study the relationships which govern the behavior and interdependence of each component of the total pest-crop system. The established relationships are expressed in the form of mathematical equations, which could be used for computer simulation of a model of the pest-crop system. This model could also be used for develOp- ment of control strategies for management of P. penetrans. The development of the model was not undertaken as part of this disseration. The research was limited to studies on the pest, the associated crop, and two other interacting components (mycorrhizae and crops grown in rotation with with navy beans. 1.4.2 Overall research objective To establish the ecological relationships which govern the behavior of the P. penetrans - Phaseolus vulgaris system. 1.4.3 Research outline 1.4.3.1 The pest system (1) (2) (3) (4) 1.4.3.2 (l) (2) Determine the field distribution of P. penetrans. Determine the incidence of P. penetrans in dry bean fields in Michigan. Develop and maintain a population of P. penetrans for use in this research study. Identify and develop a key to the stages in the life cycle of P. penetrans. Pest-crop interactions Evaluate the pathogenicity of P. penetrans associated with dry beans. Study population dynamics of P. penetrans associated with navy beans. 1.4.3.2.1 (l) (2) (3) (4) (5) (6) 1.4.4 Infl 1.4.4.1 (l) (2) Influence of environmental parameters of temperature and moisture Determine the effect of temperature on the population dynamics of P. penetrans under field and greenhouse conditions. Examine the influence of temperature on germination, growth and development of dry beans. Study the influence of temperature on P. penetrans and dry bean interactions. Determine the effect of soil moisture on the population dynamics of P. penetrans. Observe the effect of soil moisture on growth and development of dry beans. Determine the effect of P. penetrans on dry beans at different soil moisture potentials. uence of interacting components Mycorrhizae Determine the effect of mycorrhizal associa- tions on growth and development of dry beans. Examine the interactions of mycorrhizae and P. penetrans on dry beans. 1.4.4.2 (l) Rotation crops - Kidney Beans Examine the effect of P. penetrans on dif- ferent cultivars of dry beans and identify tolerant or resistant cultivars for use in the management of P. penetrans. 2.0 LITERATURE REVIEW 2.1 Pratylenchus penetrans 2.1.1 Taxonomy The root-lesion nematode (Pratylenchus penetrans) is a member of the phylum: Ashelmintha, class: Nematoda, subclass: Secernentea, order: Tylenchida, suborder: Tylenchina, superfamily: Tylenchoidea, family: Pratylen- chidae, subfamily: Pratylenchinae, and genus: Pratylenchus. It was described by Bastain in 1865, as Tylenchus obtusus. This description and illustrations, however, were in- adequate for specific identification of the species. De Man described the same species in 1880, and is generally credited with identifying the first Pratylenchus penetrans. The species was first found on potatoes by Cobb in 1917. In 1922 Micoletzy placed this nematode in a new subgenus called Chitinotylenchus and the genus Tylenchus was synonymized with Anguillulina Gervais and Van Beneden by Baylis and Daubeney in 1926. In 1934 Filipjev's classi- fication of the Tylenchida (which is the present-day classification of the group) defined Chitinotylenchus as a distinct genus excluding Pratylenchus. With the aid of the monographs of Sher and Allen (1953) and 10 11 Loof (1960), the species was placed in a new genus called Pratylenchus. The correct citation for this nematode is Pratylenchus penetrans (Cobb, 1917) Filipjev and Shuurmans- Stekhoven 1941. 2.1.2 Morphology Pratylenchus penetrans (Cobb, 1917) Filipjev and Shmnmans—Stekhoven 1941 is vermiform in all stages, with females ranging in length from 343-811 um and males varying from 300-514 mm (Corbett, 1973) . The species is characterized by its broad head with conspicous sclerotization, and a lip region which is flat in the front with well rounded margins. It has a typical tylenchoid oesophagus with a stoma containing a stomatostyle which is 13-16 pm in length. The median bulb is moderate in size and the oesophagal glands overlap the intestines ventrally in a lobe about 1.5 times the body width. The excretory pore is opposite the oesophageal—intestinal junction, with the hemizonid occupying about two-thirds of a body annule immediately in front of it. The location of the vulva is sub-equatorial, and the reproductive system is monodelphic. This nematode has a short post-uterine sac which is undifferentiated and varies in length from 1.0 to 1.5 of the vulval body width. The species is characterized by its distinctly spherical spermatheca. The tail is generally rounded with a smooth 12 tip and 15-27 annules on the ventral surface. The cuticular annulations are fine and the lateral field contains four incisures, the outer bands of which may be partly areolate, while the central field may contain oblique striae near the vulva, becoming areolate behind the vulva but not extending to the top of the tail. The male nematode is similar in morphology, with a lateral field containing four incisures extending to the bursa, occasionally with oblique lines in the central field near the mid-body. The spicules are slender with well-marked manubria and ventrally arcuate shafts 14-17 um in length. The gubernaculum is simple and about 3.9-4.2 pm in length. The tail is twice as long as the anal body diameter (Corbett, 1973). There are, however, significant intraspecific morphological variations in this species (Roman and Hirshman, 1969; Tarte and Mai, 1976). Tarte and Mai (1976), observed pronounced heteromorphism among specimens of Pratylenchus penetrans. Variations in tail shapes were distinct. Several shapes of stylet knobs were character- ized, and 50% of the specimens observed had knobs which were anteriorly flattened and indented. The shape of the spermatheca also varied from round to oval. Variations in the lateral field were present, and in some cases a fifth lateral line was observed. They concluded that environmental 13 factors and particularly host plants influenced such morphometric characters as body length and width, oesophagus and stylet length, tail terminus, growth of the ovary and shape of the median bulb. 2.1.3 Distribution and host range Pratylenchus penetrans is the most important species of this genus, causing injury to a wide range of economic plants. Members of this genus are commonly called root-lesion nematodes because of the characteristic lesions which they produce on infected roots (Godfrey, 1929). P. penetrans has a wide host range, occuring on over 350 plant species (Corbett, 1973). Host species of economic importance include field crops such as tobacco, alfalfa, cotton, soybean, dry beans; cereals e.g. wheat, corn, oats; vegetable crOps such as: tomato, potato, carrots; fruit trees such as: apple, peach, strawberry, cherry and many ornamentals and turfgrasses. P. penetrans is commonly found in the northeastern states of the U.S.A., southern Canada and Europe infecting corn and potatoes (Dickerson 33 al. 1964), onions (Bergeson, 1962), celery and other field crOps (Townshend, 1963). In the U.S.S.R., P. penetrans has been found in the roots of cotton, potato, beans, rye, wheat, tomato and straw- berry, causing significant damage (Krall and Riispere, 14 1965). This nematode has been described as the most widespread and economically important plant-parasitic nematode in Michigan (Knierim, 1963; Knobloch and Bird, 1980) 2.1.4 Life cycle Pratylenchus penetrans is an obligate parasite with overlaping primary and secondary life cycles, varying from 37-86 days, depending on temperature. The cycle is shortest at a soil temperature of 30 C, although fewer eggs are deposited at this temperature than at temperatures of 20-24 C (Mamiya, 1971). Reproduction takes place by amphimixis (Hung and Jenkins, 1969; Thistlewaite, 1970), involving cross fertilization and formation of two polar nuclei in the maturing oocytes. Chromosome division figures indicate that meiosis occurs. Eggs are laid singly in the soil or in roots of infected plants (Corbett, 1973). Mamiya (1971) estimated an ovi- position rate of 0.8-1.1 eggs per day for 35 days. First- stage juveniles are formed within the egg four to five days after oviposition, and under the influence of hatching stimuli,eggs containing the first-stage juvenile hatch to release second-stage juveniles in six to seven days after egg laying (Thistlewaite, 1970). Free-living in the soil the second-stage juveniles orient themselves towards 15 susceptible roots by a heat gradient and enter the zone of maturation in the plant roots. Adult males and females are formed following three additional molts (Figure 2.1). Soil temperatures influence the length of each stage (Mamiya, 1971) and optimum temperatures for repro- duction have been given as 21-23 C (Christie, 1959; Mamiya, 1971). Various other environmental factors such as moisture, oxygen supply and soil pH also influence reproduction, growth and survival of P. penetrans (Morgan and McLean, 1968; Willis, 1972; Corbett, 1973). Barker EE.El- (1975) also observed that the rate of reproduction was influenced by light intensity. Soil type influences survival (Townshend and Webber, 1971), which is generally higher in sandy soils as compared to heavier clay soils. P. penetrans overwinters in all stages in the soil or in the roots of infected plants, becoming quiescent by the mechanism of anhydrobiosis. Fourth-stages and adults, however, are the most important overwintering stages (Kable and Mai, 1968; Miller, 1968; Dunn, 1972). Optimum temperatures for overwintering are given as 1.0-4.5 C. Ka ogamy , 1‘__| l Adult ---~‘ r’ Amphi- mixis hubs stage I _ Adult juvenile l6 Primary cycle l 7 - Egg i ty— male C4h stage Qenile female A [hfecondary cycles/l ~\\ Embryogenesis 1 stage juvenile 1st molt 2nd stage ISt juvenile I rd 3molt 2nd stage :2) juvenile 11‘ feeding '\___ , rd nd nd 3 , stage ‘ 2 Feeding L 2 stage 11 molt juvenile juven e in soil Figure 2.1 Life cycle of Pratylenchus penetrans 17 2.1.4.1 The primary cycle The primary cycle is the first life cycle initiated by the pathogenic stages after a period of overwintering (Figure 2.1). The cycle involves periods of inoculation, incubation and infection. The exact mechanism of attraction to susceptible roots is not known. Thermotropic responses by P. penetrans have been reported by El-Sherif and Mai (1968). Klinger (1965) suggested however that the attraction of nema- todes to the roots is related to chemical stimuli, especially carbon dioxide and amino—acids. Generally attraction occurs in the immediate vicinity of the roots at distances of about 1-2 cm away. Lavallee and Rohde (1962), also observed the attraction of P. penetrans to plant roots. This theory is supported by Shepard (1970) who pointed out that nematodes are equipped with neuro-sensory systems and their behavioral patterns are influenced by environmental factors. Root exudates in the soil could possibly act as chemical stimuli and behavioral patterns of nematodes could be set into action. This could involve secretory processes of the oesophagal glands of nematodes. The behaviorial- activated nematodes could then respond to gradients of 18 stimuli such as heat or chemical substances from root exudates. 2.1.4.1.1 Inoculation Inoculation represents the period of the life cycle during which nematodes are stimulated to move towards and penetrate susceptible plant roots. The second, third and fourth stages, and adult males and females can be used to inoculate plants in research experiments, but generally fourth stage juveniles and adult males and females are the most pathogenic stages. These migrate towards the roots and with the aid of their stylets they rupture the cell wall and penetrate the plasmalemma and enter the root cortex, migrating through and between the parenchyma cells. Inoculation is temper— ature dependent (Rohde, 1963; Dickerson e; El- 1964; Sonitrat and Chapman, 1970). 2.1.4.1.2 Incubation The incubation period follows the inoculation period and ends with the appearance of plant disease symptoms. Reports indicate that incubation periods vary depending on the host plant. In some plant species the incubation period is short and root-lesion symptoms develop within a few hours producing a brown coloration in the cytoplasm of the infected cells. In other species this 19 may take several hours to occur (Mountain and Patrick, 1959; Pitcher e; 2;. 1960). 2.1.4.1.3 Infection Infection represents the stage in the life cycle following the appearance of symptoms and ending with the final response of the host plant to the pathogenic nema- tode. During the infectious period nematodes migrate into the cortex, where they feed and reproduce or move to other cortical areas of the root system. They usually align themselves with the longitudinal axis of the root, just outside the epidermis (Rohde, 1963). As the nematodes feed on the cellular material the cells become disorganized and much of the cytoplasm disappears or retreats together with the nucleus, against the cell wall. Necrosis of cells follow the path of the nematodes. That part of the epidermal layer adjacent to the nematodes becomes discolored and appears deep brown in color extending into large groups of cells. The nema- todes continue to feed on the cortical cells and later the cell walls disintegrate and cavities appear in the cortex. The walls of these cavities are sometimes lined with brown tissue. P. penetrans is an obligate parasite and does not exist in saprophase for any length of time. As soon as the nematodes become associated with dead tissue they migrate 20 away and penetrate new living tissue (Pitcher EE.El° 1960; Rohde, 1963; Dickerson EE.2l° 1964; Odihirim and Jenkins, 1965; Troll and Rohde, 1966). 2.1.4.2 Secondary cycles Secondary cycles are generally initiated by progeny of the first generation (Figure 2.1). The length of the cycles and the number of generations are largely dependent on the host plant and temperature. Secondary cycles can be initiated by migration of pathogenic nematodes from infected roots to healthy roots, or from inoculation through movement of pathogenic stages in the soil, towards susceptible roots. The stages of the secondary cycle are similar to those of the primary cycle, and result in formation of necrotic root tissue, which may slough off. Bacteria and fungi can enter the necrotic wounds, and cause a complex disease syndrome to develop (Corbett, 1973). 2.1.5 Symptomatology The intensity of symptoms of the root-lesion disease caused by P. penetrans varies depending on the host plant and environmental conditions. Within suscep- tible plant species marked differences occur in the relative amount of visual symptoms observed. In general, however, the primary symptoms appear as necrotic lesions 21 on the roots. Root-lesions first appear as tiny water- soaked spots, but these soon turn brown or almost black. The lesions appear mainly on the young feeder roots, but they may be found anywhere along the root system. Lesions generally coalesce with each other by expanding longi- tudinally along the root axis, but they may also expand laterally girdling and killing the entire root. As the lesions enlarge, the infected cells in the cortex collapse and the discolored area appears constricted. The secondary symptoms include yellowing of leaves, which reduces the photosynthetic capabilities of the plant, resulting in stunting and general poor growth of the plants. These symptoms result from the inefficient functioning of the diseased root system which is unable to allow adequate uptake of water and nutrients from the soil (Mai, 1960; Pitcher e; 31. 1960; Mountain, 1961; Dickerson g; 31. 1964). 2.1.6 Ecology Environmental conditions greatly influence population dynamics of P. penetrans and the development of plant diseases caused by root-lesion nematodes. 22 2.1.6.1 Temperature Disease development is to a large extent influ- enced by temperature, as the activity and survival of the nematodes are governed by this factor. Acosta and Malek (1979) reported on the influence of temperature on population development of different species of Pratylenchus on soybean. P. penetrans and P. scribneri showed greatest reproduction potential at a temperature of 25 C. It has been reported that P. penetrans increases in the soil in late summer and early autumn, and decreases in late spring and early summer (Di Edwardo, 1961; Miller 25 El; 1963; Ferris, 1967; Olthof, 1971; Olthof and Potter, 1973). The fluctuations are a result of migration of the nematodes in the roots early in spring and summer and out of the roots in late summer. Although the population dynamics is greatly influenced by temperature the host crop with which the nematodes are associated has a signif- icant influence on population development. The inital population density is also of great importance and Oostenbrink (1966) observed that the initial population density at the time of planting was a consistant parameter for estimating decreases in yield of the host crop. He found a significant linear relationship between initial population densities and tuber weight of potatoes 23 infected with P. penetrans. Olthof 3E El; (1973) also observed a positive correlation between yield loss and initial population densities of P. penetrans associated with potato roots. Seinhorst (1966) observed that a minimum density of 1.0 P. penetrans per gram of soil was necessary to cause damage to some crops. Oostenbrink (1966) reported that densities from 0.4 to 1.0 per gram of soil in sandy soils and densities of 0.7 to 2.0 per gram in organic or loam soil were required to cause significant reduction in yields of crOps infected with P. penetrans. El-Sherif and Mai (1966) observed a linear relationship between numbers of P. penetrans that invaded roots and numbers transferred to plants when the initial inoculum density was above 200. 2.1.6.2 Soil nutrients Population densities are also affected by soil nutrients, either directly or indirectly through the influence of soil microorganisms. Walker (1969) demon- strated that additions of nitrogen to soil decreased populations of P. penetrans. Kirkpatrick 2E.2l- (1964) observed similar responses, and noted that populations were significantly reduced in plants which received high rates of potassium. Interactions of nematicides and fertilizers can also influence population densities 24 (Vitosh e; 3;. 1978). 2.1.6.3 Soil moisture Soil moisture is essential for movement and survival of nematodes. Excess soil moisture results in detrimental effects on populations by limiting their movement and reducing their oxygen supply. In general, population densities are higher in sandy soils which are well aerated and permit retention of adequate amounts of soil moisture. Thompson and Willis (1970) reported that significantly lower root and foliage growth of Empire birdsfoot trefoil (Lotus corniculatus L.) was observed at a soil moisture level of 50% field capacity when com- pared to growth at a moisture level of 70-100% field capacity. Population development was higher at the higher soil moisture level. Kable and Mai (1968) re- ported that the rate of population increase in P. penetrans was greatest at moderate soil water potentials and least at high water potentials. They concluded that the wide- spread occurrence of high population densities of P. penetrans in sandy soils was related to an interaction of soil temperature soil moisture and soil type. 25 2.1.6.4 Interactions with fungi The root-lesion nematode disease can predispose plants to infection by fungi, e.g. Aphanomyces euteiches on peas, Fusarium oxysporum on lucerne and peas, Verticillium alboatrum and Verticillium dahliae on eggplant, peppermint, peppers, potatoes, strawberries and tomato (Miller and Edginton, 1962; Bergeson, 1963; Rich and Miller, 1964; Mountain and McKeen, 1965; Miller 23 al. 1967; Olthof and Reyes, 1969). Studies on the role of P. penetrans and Meloidogyne spp. in dry rot of kidney beans caused by Fusarium solani f. spp. phaseoli indicated that low inoculum densities of the fungus caused greater infection of dry root rot than high inoculum densities. However nematode infection had no significant effect on the severity of the disease (Hutton EE.El- 1972). Oyekan and Mitchel (1972) reported on the development of a synergistic interaction between Pratylenchus penetrans and Fusarium oxysporum in a wilt- resistant pea cultivar (Wisconsin perfection). 2.1.6.5 Nematode-Nematode interactions Reports on the interaction of nematodes and their effects on yields are limited. Freckman and Chapman (1972) reported that Heterodera trifolii (Goffart) and Pratylenchus penetrans (Cobb) did not affect the penetration 26 of either nematode on red clover roots. Studies on the dynamics of field populations of Hoplolaimus columbus and Meloidogyne incggnitia indicated that in some fields P. columbus replaced M. incognita while in other fileds the distribution of the species remained constant (Bird 2E al. 1974). Gay and Bird (1973) also reported on the influence of concomitant Pratylenchus brachyurus and Meloidogyne spp. on root penetration and population dynamics. McIntyre and Miller (1976) reported on the interactionsof Tylenchorhynchus claytoni and P. penetrans in tobacco roots. They observed that population densities of P. penetrans were reduced in roots which were pre- viously exposed to P. claytoni. 27 2.2 Navy Beans (Phaseolus vulgaris L.) 2.2.1 Importance Navy beans are an important part of the diet of many people in numerous parts of the world. They are relatively inexpensive and highly nutritious, containing high amounts of protein, and smaller amounts of phos- phorus, iron and vitamin B (Andersen, 1955). Dry beans are produced in many countries, and the major world producing countries include Brazil, U.S.A., Mexico, Yugoslavia and Italy (Martin and Leonard, 1967). In the U.S.A., the leading bean producing states include Michigan, California, Idaho, Colorado and Nebraska. Over 90% of the beans produced in the humid section of the U.S.A. are grown in Michigan and New York. Bean production ranks third in value in Michigan field crops, navy beans forming the major class of beans (Erdman e3 Ei- 1965). Total estimated 1979 U.S. dry bean acreage was 1396.6 thousand acres and total Michigan dry bean acreage was 500 thousand. Bean production has remained constant from 1978 at an estimated level of 86,000 tons. Con— sumption however, has increased and is estimated at 80,000 tons. 28 2.2.2 Marketing The canning industry forms the main market for navy beans. About 85-90% of.the beans destined for domestic consumption are canned and the remainder are packaged and sold as dry beans. Other navy bean pro- ducts include vegetable beans (beans in tomato sauce without meat), beans and ground beef, beans and weiners, beans and Vienna sausages, beans with bacon soup, beans with molasses and baked beans (Anonymous, 1971). 2.2.3 Supply and price The navy bean industry is characterized by con- siderable fluctuations from season to season. While the grower price fluctuates during a marketing season, retail prices of canned beans have remained relatively stable over the last few years. As bean production is concentrated in the Saginaw valley and the Thumb district, unfavorable weather in these areas can cause fluctuations in the total supply of navy beans. The domestic demand for navy beans is quite in- elastic. Also, there is a low influence of small Cali- fornia white beans (which is the only other bean which can be substituted for navy beans in the canning industry), on navy bean domestic demand. Therefore decreases in supply of navy beans would result in significant increases 29 in price (Anonymous, 1971). 2.2.4 Production factors affecting yield.- The main reasons for the decline in navy bean yields have been attributed to (l) unfavorable environ- mental conditions of temperature and moisture, (2) choice of bean variety, (3) cultural practices, (4) soil fertil- ity factors, (5) diseases and use of uncertified seed. 2.2.4.1 Environmental factors The navy bean plant is a warm season annual adapted to a variety of soils. Optimum temperatures for growth range from 19 to 25 C (Martin and Leonard, 1967). High temperatures interfere with seed setting while low temperatures are unfavorable for growth. Austin and MacClean (1972) observed that temperature and moisture can affect bean germination, photosynthesis and respiration. They observed that rates of photo- synthesis were lower in plants grown in low temperature regimes than for plants grown in high temperature regimes. Bean seeds germinate poorly in damp soils, and slow growing seedlings are subject to maggot injury, damping off and root rot diseases. In order to meet the moisture requirements for germination, beans are generally planted early in June in Michigan (Andersen g3 21' 1975). Adverse soil physical conditions result in detrimental 30 effectsixxdry bean production (Smucker and Mokma, 1978). 2.2.4.2 Navy bean varieties A considerable amount of research has been carried out on bean breeding and varietal development, in order to produce high yielding disease resistant varieties (Anonymous, 1971; Adams, 1978). Improved varieties include Robust, which was the first virus resistant variety, Michilite, which is not only virus free but also shows improved quality, Sanilac, which was the first upright disease resistant bush-type bean plant, Seaway, Seafarer and Gratiot which are early maturing varieties. These improved varieties are grown on approximately 80% of the bean acreage in Michigan, Ontario and to a lesser extent in New York, Chile, Australia and Hungary (Anonymous, 1971). 2.2.4.3 Cultural practices Navy bean plants thrive best in medium textured soils which are high in organic matter, and are provided with adequate drainage. Cultivation usually involves general practices for row crOps, with emphasis on seed- bed preparation and subsequent tillage for weed control. A 1977 survey of cultivation practices in bean producing areas in Michigan indicated that 35% of the farms were plowed in the spring and 61% in the fall. Two-thirds of 31 these farms showed indications of poor soil structure. Andersen £3 3;. (1975) reported that excessive tillage was practiced on many of the farms resulting in compaction problems and inefficient root growth. It is generally recommended that the soil should be tilled only when dry and only to a depth that includes the compacted zone. It is recommended that beans should be grown in rotation with suitable crops which will return substantial amounts of organic matter to the soil. In Michigan crops which are used in rotation with beans include, corn, soybean, sugarbeets, alfalfa and small grain. About 30% of the farmers, however, grow continuous beans for about 3 years and this increases conditions of poor soil structure and also encourages develOpment of some bean diseases. A number of herbicides are used effectively for weed control and Eptam is the most effective and widely used herbicide in bean production. Generally bean seeds are planted in rows 20 to 40 in. apart at shallow depths of 2.5-5.0 cm under adequate soil moisture conditions. Under favorable irrigated humid conditions a desirable stand of beans develops from use of planting rates of 40-100 lbs/acre (Martin and Leonard, 1967; Andersen gg,al. 1975). Cultivation practices, however, depend on the location, soil type and climatic conditions. The importance of choosing 32 a suitable planting density depending on location and method of production has been noted (Leakey, 1972; Williams e£_a£. 1973; Pinchinat, 1974; Edge 22 El. 1974; Mafra e; 31. 1974; Scarisbrick g}; _a_l_. a976). 2.2.4.4 Soil fertility factors A considerable amount of research has been carried out on the fertility requirements for bean production (Lange 33 El- 1958; Barker 2E.2l- 1966; Bans, 1967; Shea 23 El- 1968; Melton 22.2l' 1970; Mugwira and Knezek, 1971; Edge 32 a1. 1975). Beans respond more favorable to a long-term soil improvement program involving growing of green manure, fertilized leguminous forages and similar fertility enhancing practices, than they do to direct application of fertilizers (Rather, 1942). Moreover, germinating seedlings can be injured by the direct appli- cation of commercial fertilizers. This can be avoided by correct placement of the fertilizers. Andersen 25 El; (1975) reported that beneficial results can be achieved from band application of fertilizer at planting time. Studies on fertility requirements for bean production indicate that nitrogen and phosphorus are the two most important soil nutrients which are needed for adequate growth. The leguminous nature of navy bean plants enable them to obtain some of their nitrogen requirement from 33 symbiotic associations with nitrogen-fixing bacteria - Rhizobium phaseoli. Edge 33 2l° (1975) described bean plants as poor nitrogen fixers. Application of nitrogen fertilizers is necessary in fields which show nitrogen deficiency. In most soils nitrogen fertilizers appear to be more effective when added in the nitrate rather than in the ammonium form (Barker gt El- 1966). Zinc, phosphorus and lime inter- actions with bean yields have been studied (Melton 33 al. 1970; Mugwira and Knezek, 1971). Reports indicate that yields on acid soils are generally decreased when zinc is applied. Ruschel gt 3l° (1966) also observed effects of interactions between nitrogen fixation and other nutrients on bean yields. 2.2.4.5 Bean diseases Navy beans are susceptible to a number of diseases caused by bacteria, fungi, viruses, insects and nematodes. Three types of bacterial blights have been observed in bean fields. These include, common bacteria blight caused by Xanthamonas phaseoli, fuscous blight caused by Xanthamonas phaseoli var fuscans, and halo blight caused by Pseudomonas phaseolicola. Andersen gt El; (1975) reported the presence of common and fuscous blights in 75 bean fields in Michigan. Rains, 34 heavy dew and humid weather favor the development of the disease. The common and fuscous blights are enhanced by warm weather while halo blight is promoted by cool weather. A number of fungal diseases are known to affect bean production. These include bean anthracnose caused by Colletotrichum lindemuthianum, sclerotina wilt or white mold caused by Sclerotinia sclerotium, fungus root rots caused by Fusarium solani, E. phaseoli, damping off and seed decay caused by Pythium aphanidermatum, Pythium debaryanum and Rhizoctonia solani. Two virus strains, Phaseoli virus 1 and 2 can also cause bean diseases. Extensive breeding programs have resulted in the production of some disease resistant varieties. The Sanilac variety is resistant to bean anthracnose, and to Phaseoli virus 1 strain which causes common bean mossiac disease, but it is moderately suscep- tible to g. phaseoli and E. phaseoli var fuscans, which cause common and fuscous bacterial blights. The Monroe bean variety is resistant to both virus strains, while Michilite is partially resistant to virus 1 strain. Most of the other bean varieties grown in Michigan are susceptible to these diseases. Management strategies involving suitable crop rotation, use of certified seed, use of bactericides and fungicides can be effective in 35 controlling these diseases. 2.2.4.6 Nematode diseases Reports on nematode diseases of dry beans indicate that the crop is susceptible to a number of nematode species within many genera such as, Meloidogyne, Heterodera and Pratylenchus (Blazey 35 El; 1964; Rhoades and Beeman, 1967; Sen and Jensen, 1969; Taylor et El° 1970; Hartmann, 1971; Ngundo and Taylor, 1974; Freire, 1976; Thomason 25 El- 1976). Blazey gt El. (1964) investigated the resistance of 55 common bean varieties to Meloidogyne incognita. Seventeen varieties were found to be partially resistant but not immune to this species, for occassionally small galls and females were found even in resistant varieties. Freire (1976), in a study of nematodes associated with beans, found M. incognita, M. iavanica, Helicotylenchus nanus, Criconemoides spp., Pratylenchus brachyurus, Hemicycliophora lutosa and Xiphenema spp. in the rhizosphere of the bean roots. Considerable reduction in yields were observed in bean plants infested with M. incognita and M. javanica. 36 2.3 Symbionts in Association with Nagy Beans 2.3.1 Mycorrhizae Many plants are known to form symbiotic mycorrhizal associations which enhance their growth. The fungus provides the plant with nutrients while the plant in return supplies the fungus with carbon in the form of carbohydrates which are assimulated through the photosynthetic activity of the plant. Mycorrhizae can be classified as ectomycorrhizae, endomycorrhizae and ectendomycorrhizae. The ectomycor— rhizae produce a hypal mantle around the plant roots and an intercellular cortical net of hyphae known as the Hartig Net. Endomycorrhizae are charac- terized by hyphae which form a loose fungal network in the soil, and also penetrate the root cortex inter and intracellularly. Ectendomycorrhizae exhibit features of both ecto— and endo-mycorrhizae. They form a hyphal mantle and also penetrate the root cortex intracellularly. Endomycorrhizae are fungi of the Endogonaceae (Phycomycete) and can be divided into septate and non- septate fungi (Gerdemann, 1969). Vesicular-arbuscular mycorrhizae are found in four genera of the Endogonaceae. These are: Gigaspora, Glomus, Acaulospora and Sclerocystis. Vesicular-arbuscular mycorrhizae have been described as 37 being dimorphic and composed of thick-walled non-septate hyphae, with thin-walled side branches which may lay down septa (Nicolson, 1959; Mosse, 1977). Hyphae of variable sizes are found within the root cortex, but the stele is not infected. Arbuscles which are specialized haustorical structures of the fungus are formed intra- cellularly as a result of extensive dichotomous branching of the main infection hyphae (Cox and Sanders, 1974). These arbuscles aid in the symbiotic association with plants. Thin-walled spherical structures known as vesicles may be produced intercellularly or intracellularly in the cortical tissue. Vesicular-arbuscular mycorrhizae produce globose, subglobose or eliptical to avoid spores which contain globules of oil. Gigaspora produces azygospores which are borne singly in the soil. These are subglobose and are borne terminally on a bulbous suspension-like cell. The most widespread V—A endomycorrhizal fungi are found in the genus Glomus (Gerdemann and Trappe, 1974). These fungi produce chlamydospores which are borne on undifferentiated nongametangial hyphae. Spores are usually terminal, however intercalary spores and spores with more than one basal attachment sometimes occur. Two important species of the genus commonly found in Michigan are Glomus fasciculatus and Glomus mossea 38 (Kotcon, 1978; Bird and Safir, 1979). Beneficial effects obtained from mycorrhizal associations have been attributed to increase in the absorption surface provided by the extensive branching hyphae of the fungi in contact with soil nutrient reserves. Increases in growth have been related mainly to increase in uptake of phosphorus, but increases in uptake of water, nitrogen, potassium, boron aluminium¢manganese and zinc have also been observed (Ross and Harper, 1970; Ross, 1971; Sanders and Tinker, 1971; Ross, 1972; Hattingh gt gt. 1973; Mosse gt gt. 1973; Bird, 1974; Tinker, 1975; LaRue gt gt. 1975; Bowen gt gt. 1975; Safir, 1977). I Environmental factors such as temperature, light and moisture can affect the development of mycorrhizal associations (Mosse, 1973; Hayman, 1974; Furlan and Fortin, 1977). The degree of mycorrhizal infection may vary greatly depending on the degree of shading which plants receive (Hayman, 1974; Redhead, 1975). The relationship between mycorrhizal infection and soil moisture is not clearly defined, but this is influenced largely by the soil type, the mycorrhizal fungus and the host plant. Generally, optimum soil water required for plant growth enhances mycorrhizal infection. Tinker (1975) reported that soil fertility 39 factors influence the development of mycorrhizal associations. Generally soils of low fertility favor mycorrhizal infection while soils of high fertility levels may even retard the development of mycorrhizal associations. Mosse (1977) however observed that mycorrhizal associations can be established in soils which contain high levels of phosphorus when relatively high levels of mycorrhizal inoculum are used. The beneficial effects of mycorrhizal associations are therefore of greater significance in soils of low to moderate fertility. Reports indicate that mycorrhizal associations can influence the development of plant diseases. Vesicular-arbuscular mycorrhizal interactions with pathogenic organisms have been observed (Schenck and Kinlock, 1974). Reduction of infection by Thielaviopsis basicola in mycorrhizal plants was observed (Baltruschat gt gt. 1973; Schonbeck and Dehne, 1977). Ross (1972) observed interactions of Phytophthora megaspermae var sigae and vesicular-arbuscular mycorrhizae associated with soybeans. Daft and Okusanya (1973) reported that tomato aucuba mossiac virus increased in plants as the mycorrhizal infection increased. Mycorrhizal onion roots however are less susceptible to pink root diseases caused by gyrenochaeta terrestris (Safir, 1968; 4O Becker, 1976). Mycorrhizal-nematode interactions are complex. O'Bannon gt gt. (1979) observed that t. semipenetrans infected roots grown in infested g. mossea soil did not show evidence of vesicle development but arbuscular development was observed. Interactions of Heterodera solanacearum and vesicular-arbuscular mycorrhizae reduced mycorrhizae and nematode densities and also yield of Tobacco (Fox and Spasoff, 1972). Studies on interactions of Meloidogyne spp. and Heterodera spp. and vesicular-arbuscular mychorrhizal fungi indicated that high population densities of Meloidogyne spp. were associated with low densities of mycorrhizal spores (Schenck and Kinlock, 1974; Schenck gt gt. 1975). The results of Schenck gt gt. (1975) support the findings of Baltruschat (1973) indicating an antagonistic relationship between vesicular-arbuscular mycorrhizae and low nematode densities. Schenck gt gt. (1975) also pointed out that the species of mycorrhizae influenced the nature of the interaction between vesicular- arbuscular mycorrhizae and nematodes. Interactions between mychorrhizal fungi and nematodes are not always detected. Hussey and Roncadori (1978) observed no interaction between Pratylenchus brachyurus and 41 vesicular-arbuscular mycorrhizae, but plant growth was increased by vesicular-arbuscular mycorrhizae. 3 . 0 EXPERIMENTAL 3.1 General Procedures 3.1.1 Soil samples 3.1.1.1 Field samples Soil samples were taken by inserting a conical shaped nematode soil sampler to depth of 5-15 cm in the soil. Six soil cores were taken to fill the soil sampler. The soil was then transferred to plastic bags and stored at 4 C until they were processed for nematode densities. 3.1.1.2 Greenhouse samples The total quantity of soil in a pot was taken as the soil sample. 3.1.2 Root samples 3.1.2.1 Field samples Bean plants were uprooted with the aid of a narrow bladded shovel. Roots from six plants were taken to make a composite sample. 3.1.2.2 Greenhouse samples The entire root system was carefully removed and used to represent a sample from one replicate of 42 43 any treatment. 3.1.3 Nematode extraction 3.1.3.1 Soil samples A modified centrifugation-flotation technique (Jenkins, 1964) was used to extract nematodes from soil samples. Both living and dead nematodes were recovered with this method. In this method 100 cm3 of soil from the composite sample were added to three gallons of water in a plastic pail. The soil was mixed for three minutes and the sediment was allowed to settle. The soil suspension was poured through a 100 mesh sieve on to a 400 mesh sieve. The soil with nematodes was then washed from the sieve into a 20 ml centrifuge test tube. The soil suspension was centrifuged at 42g for 4.5 min. The tube was removed from the centrifuge and the supernatant liquid was decanted. A sucrose solution with a specific gravity of 1.14 was added to the soil and contents were thoroughly mixed and centrifuged again for 2.5 min. The supernatant liquid containing the nematodes was poured on to a 400 mesh sieve and the nematodes were washed from the sieve :into 5 ml test tubes. 3.1.3.2 Root samples Nematodes were extracted from the roots by a shaker technique. In this method two 9 of root tissue 44 were placed in a 125 or 250 m1 flask, and 50 ml of an incubation solution (a mixture of 10 ppm Ethoxyethyl mercuric chloride (EMC) and 50 ppm Dihydrostreptomycin sulfate (DSS)), was added to the flask and placed on a gyratory shaker at 100 rpm for three days. Nematodes were recovered by decanting the solution from the flask on to a 400 mesh sieve. Nematodes were washed from the sieve into 5 ml test tubes. 3.1.4 Identification and calculation of nematode population densities Five ml suspensions from nematode extraction procedures were poured into calibrated petri dishes divided into 10 longitudinal sections. Nematodes were identified and the number of nematodes in 2 sections (1/5 area) of the petri dish were enumerated with the aid of a compound microscope and a stereoscope. Enumerated values, multiplied by 5 were averaged to express density per 100 cm3 soil and density per 1 9 root tissue, respec- tively. At low densities the number of nematodes in each section of the petri dish were counted. 3.1.5 Extraction of vesicular-arbuscular mycorrhizal spores from soil Vesicular-arbuscular mycorrhizae spores were extracted from soil using a modified centrifugal-flotation 45 technique. The method was similar to that outlined in Sec. 3.1.3.1 with a slight modification in the specific gravity of the sucrose solution. In this method for extracting vesicular-arbuscular spores a sucrose solution with a specific gravity of 1.37 was used. 3.1.6 Identification of vesicular-arbuscular mycorrhizae in root samples Internal hyphae and vesicles were observed by a staining technique. In this method 2.0 g of root tissue were cut thinly and immersed in 10% Potassium hydroxide (KOH) for one hour. The roots were rinsed with distilled water and acidified in 10% Hydrochloric acid (HCL) for one hour. The roots were then removed from the acid and stained with acid fuschin-lactophenol solution for 30 min. Roots were cleared in lactophenol. Arbuscles, vesicles and hyphae were identified with the use of a Spencer compound microscope and percentage root infection was calculated. 3.1.7 Converting time to accumulated degree days Sampling dates were expressed as the number of accumulated heat units, termed degree days. These heat units or degree days represent the amount of energy 46 available for growth and development of organisms and plants. The daily minimum and maximum temperatures were used to calculate degree days and the sum of degree days for each sampling period was calculated as the accumumlated degree day value. The base temperature used for calculation of degree days was 10C. Daily temp- eratures were recorded in degree fahrenheit and a conver- sion factor of 0.556 was used to convert degree days from degrees fahrenheit to degrees centigrade. The equation for accumulated degree days is: (9010C) = (Min T + Max T) - 50) x 0.556 2 where DDlO C is accumulated degree days at base 10 C Min T = Minimum temperature in degrees fahrenheit Max T Maximum temperature in degrees fahrenheit (Vander Brink gt gt. 1977). 3.1.8 Plant growth analysis Quantitative growth analysis involving use of growth indeces was conducted. The effect of P. penetrans on relative growth rate of plants and leaf area ratios were examined. The relative growth rate provides a valuable overall index of plant growth. The mean value of relative growth rate (R) was calculated using the equation: 47 1 _ 1n dkz 1n dWl Tz’Tl relative growth rate per week where R W2 = dry weight of navy bean shoot system at time T2 2 ll 1 dry weight of navy bean shoot system at time T1 T = time in weeks Leaf area ratio represents the ratio of leaf area to total plant shoot dry weight (Evans, 1972). This growth index was calculated using the equation: LAR=_L_ W where LAR = Leaf area ratio L = leaf area W = shoot dry weight 3.1.9 Soil moisture characteristic curves Soil moisture characteristic curves for three soil types were developed using the method described by Richards (1965), and modifications of this method. The method involved estimation of percent moisture associated with specific matrix potentials, with the use of pressure plates. The percent gravimetric moisture was calculated from the equation: % Gravimetric = Weight of soil water x 100 m°15ture Weight of oven dried soil 48 and the percent volumetric moisture was calculated by multiplying the gravimetric moisture by the bulk density of the soil: % Volumetric Wt. ofSOil H20 Wt. of O.D. 5011 x 100 . = x mOisture Wt. O.D. soil Volume of soil % Volumetric moisture = % grav1metr1c m01sture x bulk den51ty Wt. O.D. soil Volume of soil where bulk density oven dried soil O.D. soil 49 3.2 Pest System 3.2.1 Field distribution of Pratylenchus penetrans 3.2.1.1 Method A field site measuring 238.60 x 15.24 sq. m in size covered with a rye cover crop was used to study the field distribution of Pratylenchus penetrans in 1977. The field was divided into 184 plots. Each plot measured 3.81 x 3.81 sq. m in size (Figure 3.1). A soil sample consisting of six soil cores was collected from each plot. Four of these plots were randomly chosen and each plot was divided into 16 subplots, each subplot measuring 0.96 x 0.96 sq. m in size (Figure 3.2). A soil sample consisting of six soil cores was taken from each.subplot. One of the 16 subplots was selected from each of the four main plots. Six soil samples each consisting of one soil core were taken from the selected subplots within the four main plots (Figure 3.2, A, B, C, D). Following sampling the field was divided into two equal sections. The upper half of the field was ploughed while the lower half was left with the rye cover crop. The field was allowed to remain as described over the winter. In the spring (April, 1978), the field 50 Figure 3.1. Plot plan for the study of the field distribution of Pratylenchus penetrans. a, - 9101 :u l 2 3 4 A 8 7 6 5 9 ’ 10 ll 12 f l 16 15 14 13 y-mnm l 2 3 4 C 8 7 6 5 9 10 ll 12 16 15 l4 l3 Figure 3.2. y-nmu 1 2 3 4 I l 8 7 6 i 5 g 9 1o 11 12 I 16 15 14 13 '- - no: 173 1 2 3 4 8 7 6 5 9 10D 11 12 z i J g . 16 15 14 ' 13 5 Sampling scheme for subplots. 52 was divided into 184 plots. The above sampling scheme was repeated (Figure 3.3) and soil and root samples were taken from the lower half of the field covered with rye. In June, 1978 the upper half of the field was divided into 48 plots for a randomized block design experiment. Each plot was 6.09 x 3.46 sq. m in area (Figure 3.4). The lower half of the field was divided into 24 plots measuring 12.18 x 6.92 sq. m in area respectively (Figure 3.4). A soil sample consisting of six soil cores was collected from each plot. Soil and root samples were analysed for densities of P. penetrans (3.1.3-3.1.4). The data were analysed for variance/mean ratios. Other indeces of dispersion including Green's index, the dispersion constant K and the reciprocal of K (1/K) were also calculated. The chisquared test was used to determine whether the distribution was random, aggregate or regular. Goodness of fit test for a negative binomial distribution was applied to test the distribution from the initial sampling scheme (Figure 3.1-3.2). 3.2.2 Incidence of Pratylenchus penetrans in dry bean fields in Michigan 3.2.2.1 Method In order to determine the significance and nature of nematode problems in Michigan dry bean Figure 3.3. 53 PLOUGHED RYE COVER CROP Plot plan for the study of the field distribution of Pratylenchus penetrans in the ploughed and unploughed sections of the field. 54 Cgmzmnbsoawmmawww NHH coupon 21 2'4 Figure 3.4. Plot plan for the randomized block designs. 55 production, a survey on the incidence of nematodes in 80 dry bean fields was conducted. The 80 sampling sites were selected from a total of seven counties (Figure 3.5). Fifteen sampling sites were selected in Bay and Montcalm counties respectively. Ten sampling sites were selected in the other five counties of Huron, Saginaw, Tuscola, Sanilac and Gratiot respectively. Each sampling site consisted of one hectare (10,000 sq. m). Two soil and root samples for nematode analysis were collected from each site (3.1.1.1 and 3.1.2.1). Nematodes were extracted, identified and enumerated (3.1.3-3.1.4). Information on associated soil tvpe and bean variety was collected. The percent occurence of nematode species in each county was determined. 3.2.3 Development of an experimental population of Pratylenchus penetrans 3.2.3.1 Method A culture of g. penetrans was developed on navy beans to provide a source of inoculum densities for greenhouse experiments. One hundred navy bean plants cv Sanilac were propagated in sterilized sandy clay loam soil in the greenhouse. One week after germination, two holes were made in the soil around the bean roots, 56 State of Michigan 1 . 1, Mont - Montcalm county u__,;: Hur Bay = Bay county t ! ~"~f’ Gra = Gratiot county 1_J_Péxx_m VS Sag = Saginaw county ‘ ‘ {Lug-1. an Tus - Tuscola county ' 1Gra'_ffj "4 F- Hur - Huron county E—_—T—__J San - Sanilac county ' i l 4- % #L—vr 4 0 a O o 0 It!“ Figure 3.5. Counties included in a survey of g. penetrans in dry bean fields in Michigan. 57 and one male and one female g. penetrans suspended in 50 m1 of water in beakers were added to the ho1es in the soil. The holes were sealed and plants were watered daily. Population densities were allowed to develop for a period of ten months. Sanilac navy beans were planted three times during this period. Soil and root samples were taken (3.1.1.2 and 3.1.2.2) and nematodes were extracted, identified and enumerated (3.1.3-3.1.4). The extracted nematodes from this population were used to inoculate roots of navy bean plants which were propagated in sandy clay loam soil in large culture boxes in the greenhouse. Navy beans were replanted regularly to maintain the population of g. pgnetrans. Inoculum densities of g. penetrans for greenhouse experiments were obtained from populations developed in these culture boxes. 3.2.4 Identification of the life cycle stages of Pratytenchus penetrans 3.2.4.1 Method In order to study the population dynamics of 3. penetrans it was necessary to identify and develop' a key to the different stages in the life cycle of' P. pgnetrans. Navy bean roots were taken from the' 58 culture boxes and g. penetrans were extracted from these roots (3.1.3.2). Temporary slides of different stages (identified visually) were prepared. Morphometric characters of (a) body length (b) body width (c) oeSOph- agus length (d) ovary length and (e) anal length were measured with the use of a calibrated ocular micrometer in a compound microscope. Allometric characters of (l) "a" value (body length/body width) (2) "b" value (body length/oesophagus length) and (3) "c" value (body length/anal length) were calculated. The biomass of nematodes was calculated as: ((Bodywidth)2 x (Body length)) (Andrassy, 1956; Norton, 16 x 100,000 1977). The data were statistically analysed to determine mean values for each stage, standard deviations and coefficients of variation. Analyses of variance and Student Newman-Keuls test were applied to determine significant differences in morphometric and allometric characters among different stages in the life cycle of P. penetrans. A key to the life cycle stages of P. penetrans based on differences in morphometric and allometric characters was developed. 59 3.2.5 Results 3.2.5.1 Field distribution of P. penetrans The variance/mean ratios for all sample sets were greater than one by the chi-squared test (Table 3.1). The chi-squared test indicated that the distribution of g. penetrans over the whole field (Figure 3.6) was aggre- gated (Table 3.1A). The distribution was also aggregated in subplots from which 16 samples were taken (Figure 3.7; Table 3.18). The degree of aggregation was lower in sub- plots from which soil samples consisting of one soil core was taken (Figure 3.8; Table 3.1C). For two of these sets agreement with a random distribution was obtained by the Pearson Hartley statistic (Elliott, 1973; Table 3.1C). This random distribution was supported by the high recip- rocal K values (Table 3.1C). Goodness of fit test for a negative binomial dis- tribution indicated that the field distribution of g. penetrans determined for the sampling scheme involving the whole field (Figure 3.6) was significantly correlated with a negative binomial distribution (Table 3.1). The distribution of g. penetrans in the unploughed section of the field covered with a rye cover crop (Figures 3.9-3.17) was aggregated (Table 3.1D-L) except for one sample set (Table 3.11). The distribution of total popula- tion densities in roots plus soil was of an aggregate 6O nuxwv X Aalcvmm x N AHIAM \vau xoocfl m.cmmuw AG\NmV I x val NI mEmnom mCHHQEmm mumHmEoo Huguwcfi UI< m 662 m m~.m mm.o 6H.m mo.o mm.m om.mm om.m 6 o m 662 a 6N.m mq.o mm.m no.0 ea.m ea.oe GH.NH 6 mo soocmm m ~6.m mH.o am.m om.o om.NH e6.~ mm.¢ o No souamm m mm.6 mo.o HG.NH Ho.o 6~.H 66.6 66.m 6 Ho m 662 H a6.H m6.o so.~ mo.o Hm.m om.mm om.mH 6H «m m mmz m mo.e mm.o HG.H so.o mo.» mm.mm am.HH 6H mm m 662 m «m.o mm.o ms.a 6o.o No.6 oo.oaa m~.~H 6H mm m 662 H o~.H sa.o mo.H mo.o NH.4H mm.mm~ ma.ma 6H Hm m 662 m om.m mw.o mm.H moo.o mm.a om.mmH ma.m~ sea a coflusnfluumflo mo mx M\H mx m HMWMM m mm m .02 w Hm>wa . mm mHmEmw mcmuumcmm m5:o:mahflmum mo :oflusnfiuumflc wamflm mo mflmwamcd “H.m manna 61 Eoommum mo mwmummp u > 16 - >6\,- x6 6 n 6 6mmHQEmm HHOmV @060 Hm>oo mmu SDHB omum>oo @666m mo MHmc 66306 How mEmnom mcHHQEMm min = 66.66 66.6 66.66 666.6 66.6 66.666 66.66 6 66 = 66.66 66.6 66.6 66.6 66.66 66.66 66.6 6 66 = 66.66 66.6 66.6 66.6 66.6 66.66 66.6 6 66 = 66.66 66.6 66.6 666.6 66.66 66.666 66.66 6 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 6m = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 6m = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 66 666666666 66.66 66.6 66.6 666.6 66.66 66.6666 66.66 66 6 666666666666 6 6\6 6 66666 x 6 6 .oz 6 66>66 6 m.cmmuo mm m I mamfimm 6.666 6.6 66666 62 AmmHQE6m 60066 mwu £663 Umnm>oo ©6666 mo 666: 66306 nom menom wHQEmm HIU . 66.66 66.6 66.6 66.6 66.66 66.666 66.66 6 = 66.66 66.6 66.6 66.6 66.66 66.666 66.66 6 666666666 66.666 66.6 66.6 66.6 66.66 66.666 66.6 6 606666 66.66 66.6 66.6 66.6 66.6 66.66 66.6 6 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.6 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 666666666 66.66 66.6 66.6 66.6 66.66 66.6666 66.66 66 606666666666 6 6x6 6 66666 m 6 x 6 6 m.cwmuo mm - N I mHQEmm 6.600 6.6 66666 66006 mSHQ 660mv mmu £663 omum>oo ©666m 60 666: 66306 636 How mEmnom mHmEmm AIh 63 = 66.66 66.6 66.6 66.6 66.66 66.666 66.66 6 6 = 66.66 66.6 66.6 66.6 66.6 66.666 66.66 6 66 = 66.66 66.6 66.6 66.6 66.66 66.666 66.66 6 66 = 66.66 66.6 66.6 66.6 66.6 66.666 66.66 6 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 66 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 66 666666666 66.66 66.6 66.6 66.6 66.66 66.6666 66.66 66 6 coflusnfluumHQ x M\6 M xmocH x m x .oz 6 Hm>ma 6 m.cmmuw mm m I mHmEmm 6.600 6.6 66666 muOHQ 6m mo cmflmmw x0063 cmN6Eowcmu map How mamnom mamfimm I O macam m6 m0 cmflmmc x0069 chHEOUCMH map How wamnom $6056» I A camflm mo mam: wmnmson map How mamnom mamfiwm oIz 64 = 66.666 66.6 66.6 66.6 66.66 66.6666 66.66 66 o = 66.666 66.6 66.6 666.6 66.6 66.666 66.66 66 6 = 66.66 66.6 66.6 66.6 66.6 66.66 66.6 6 6o = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 6 6o = 66.66 66.6 66.6 66.6 66.6 66.66 66.6 6 N0 = 66.66 66.6 66.6 66.6 66.66 66.666 66.66 6 6o = 66.66 66.6 66.6 66.6 66.6 66.66 66.66 66 62 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 62 = 66.66 66.6 66.6 66.6 66.6 66.66 66.6 66 N2 = 66.666 66.6 66.6 66.6 66.66 66.666 66.66 66 62 666666666 66.66 n 6 66.6 66.6 66.6 66.66 66.666 66.66 66 z cofiusnwuumwo x x\6 M xmocH x m x .02 a Hm>ma a m.:wmuw IMMWI. m I mamemm u.coo 6.m manna 18 16 36 17 26 10 26 N 0" o 11 21 7 23 14 25 H 5.; 0'0 13 30 42 38 ...- \l N O N N f-‘kho \N \N to W O #3 O—l M 0-4 \N N \N p... U1 ES w H 1: ... .1: VJ \J a O D t: H O5 CO 25 \N C) 5.; O 5... O on .... on H \N m 12 \J \D H N N \l H U1 \3 \N \N \J ... U1 31 10 H \l N \n LN N N V \N N w .... ... \l N N J: .2 01 0 S 24 19 20 7 7 20 8 38 7 23 21 13 18 18 13 0 10 22 9 1H 0 Q 10 10 0 0 0 42 12 38 1“ 2“ 10 3 12 18 Figure 3.6. Distribution of g. penetrans in the field. 66 l1 - PLOT III III 36 o 6 26 a II 5 u u a a 20 2 38 no a, - PLOT 122 12 17 22 0 Is 18 0 ‘ 25 30 19 5 15 2 3 2 Figure 3.7. Distribution of g. 32 — 9101 52 36 23 11 a a 10 o a o 15 5 1s 27 a s 25 3n - 9101 173 6 2 0 so 16 6 23 o 10 2 19 9 19 1s 21 18 penetrans in subplots c1 - PLOT zn cu - PLOT 173 Figure 3.8. Distribution of P. penetrans from samples 67 g-nmn VI c3 - PLOT 122 13 12 15 consisting of one soil core. 68 33 O 28 59 16 2' 3 21 0 133 12 16 84 19 16 14 2 77 0 86 0 23 35 31 ll 2 0 52 66 12 41 15 7 21 114 4 0 4 5 0 22 10 45 39 2 l 7 16 4 65 74 48 94 118 28 52 2 19 34 20 4 85 84 100 0 52 30 12 Figure 3.9 Soil distribution of g. Benetrans from the section of the field covered with rye. [1- PLOI 96 (S0IL) 69 E2- PLOT 1u2 (SOIL) 17 3a a 2 32 o 32 35 2 21 6 2 2;. 23 63 6 o 6 o In 12 16 23 20 63 56 3o 0 2 7 16 o :3 - PLOT 16a (SOIL) Eu - PLOT 17s (soIL) 23 9 20 21 ° ° 2° 13 1“ 3 o 10 7 6 7 o o 62 0 2 a o 32 32 o o o a 2“ 2° 3° 1“ Figure 3.10. Soil distribution of P. penetrans in subplots from the section of the field covered with rye. 70 1’1 - PLOT % (SOIL) 72 - PLOT 142 (SOIL) 14 24 F3 - PLOT Isa (SOIL) I“ - PLOT 17S (SOIL) _ ......J— .--- t - Figure 3.11. Soil distribution of g. penetrans from samples consisting of one soil core from the section of field covered with rye. 71 15 73 164 25 14 27 42 16 16 3 35 0 8 13 6 102 20 20 0 4 12 16 14 2 7 12 0 2 3O 28 10 156 80 17 2 2 102 46 50 30 0 10 0 0 60 28 31 96 180 44 43 34 O 15 4 0 36 38. 4 0 20 7 44 5 9 2 46 0 14 0 16 1 3 Figure 3.12. Root distribution of g. penetrans in the section of the field covered with rye. H1 - PLOT % (M15) 72 O 12 0 2 26 4 2a 1a 0 0 64 24 28 0 8 21 H3 - PLOT 164 (ROOTS) 8 2 0 35 12 4 6 2 4 32 0 6 5 14 4 7 Figure 3.13. H2 - PLOT 112 (ROOTS) 7 35 15 0 21 10 3O 37 56 % 56 50 21 16 27 In H“ - PLOT 175 (loom 12 0 0 0 7 144 18 1a 33 20 12 a 28 56 2O 56 Root distribution of E. penetrans in subplots from the section of the field covered with rye. 73 [1 - PLOT % (”“51 12 ‘ PLOT 1‘2 (“15) l3 - PLOT 166 (ROOTS) I. - PLOT 175 (mars) 10 o Figure 3. 14. Root distribution of g. penetrans from samples consisting of one core from the section of the field covered with rye. . 74 31 12 34 16 18 70 243 35 47 27 70 75 40 21 68 37 u 175 96 |._.I O 00 LO 0'3 N o l 8512M I._.I \l \N LO LD 00 I——l 00 ...a Iv—‘U'1\l U4 LDii—‘CDU‘IJ: 69 74 48 132 122 28 72 _§§1__§2.__29_. 131 an 104 ¥ 0 68 31 15 B H6 Figure 3.15. Distribution of g. penetrans (soil + root) in the section of the field covered with rye. 75 x, - PLOT as (SOIL . IIOOTS) :2 - PLOT 162 (SOIL . Inn) 17 62 Q a 39 35 I7 35 as 36 93 :3 a 5 w m o 6 a n a 12 u m 91 56 33 21 22 23 I3 1- x, - PLOT 16 (S011 . IIOOTS) TO, - PLOT 173 (SOIL . mTS) n u m s n o m u n 7 6 u n m a n . a o . n m u w s n 3 7 9 n m m Figure 3.16. Distribution of g. penetrans (root + soil) in subplots from the section of the field covered with rye. 76 L1 - PLOT 96 (SOIL . IIOOTS) L2 - PLOT 1:12 (SOIL . ROOTS) 10 42 21 8 25 13 14 2h 39 L3 - PLOT 16a (SOIL . ROOTS) L. - PLOT 17s (SOIL . IIOOTS) 69 31 16 Figure 3.17. Distribution of P. penetrans _ (root + soil) from samples consisting of one core from the section of the field covered with rye. 77 nature (Table 3.1J_L). The mean numbers of P. penetrans in the ploughed section of the field (Figures 3.18-3.20; Table 3.1M, N, 0) were higher for the large sample set of 92 plots (Table 3.1M) compared to the mean numbers of P. penetrans from the smaller subplots from which 16 and 6 samples were collected (Table 3.1N, O). The variance/ mean ratios were greater than one indicating an aggregate distribuiton. The distribution in the randomized block design plots was also aggregate (Figure 3.21; Table 3.1P, Q). 3.2.5.2 Incidence of P. penetrans in dry bean fields in Michigan The survey of 80 dry bean fields in Michigan indicated that plant-parasitic nematodes inhabit dry bean fields. The two most commonly recovered genera were root-lesion nematodes (Pratylenchus spp.) and stunt nematodes (Tylenchorhynchus spp.) (Table 3.2). Pratylenchus spp. were found in 68% of the 80 fields and Tylenchorhynchus spp. were present in 45% of the 80 fields. Pratylenchus penetrans was the most pre- dominant Pratylenchus spp. observed in dry bean fields. The percent occurrence of Pratylenchus spp. increasedtur county in the following orderiSaginaW>IHuron> Sanilac> Gratiot Bay >Tuscola.>Montcalm (Table 3.2). This is as expected in the sandy clay loam soil characteristic of Montcalm county. 78 35 9 8 25 4 9 9 28 0 16 9 28 24 3 7 13 0 79 75 17 4 5 12 13 0 75 19 17 49 49 22 O 59 2 6 11 28 29 18 10 8 49 7 8 19 29 15 10 29 O 16 29 13 15 25 2 5 0 48 10 5 6 24 19 5 14 5 19 25 5 10 5 5 29 25 15 29 19 Figure 3.18. Distribution of P. penetrans in the ploughed section of the field. I1 - PLOT 15 (PLOUGHED) I2 - PLOT 2a (PLOUGHED) 25 15 O 5 28 19 1s 16 5 16 5 23 O 25 15 so I; - PLOT 52 (PLOUGHED) 16 20 O 25 12 5 10 no 20 no 10 5 O 5 25 10 5 15 o 16 2 17 O 5 1s 16 O 25 15 13 1O 5 O. - PLOT 7s (PLOUGH£D) 17 1O 5 12 20 5 25 16 a 5 O 16 12 1o 5 O Figure 3.19. Distribution of P. penetrans in subplots in the ploughed section of the field. 80 0 1O 42 13 5 2 o; - PLOT 52 TPLOOOHLO) ou- PLOT 7s (PLOUGHED) H0 20 0 16 Figure 3.20. Distribution of g. penetrans from samples consisting of one soil core in the ploughed section of the field. 81 P- (“8 PLOYS) 0- (2H PLOTS) 70 91 34 9“ 102 61 65 35 31 20 18 38 5a 99 133 24 21 66 134 68 “2 Figure 3.21. Distribution of g. penetrans in randomized block design plots. .ummB mason mcmezwz uchsum on» on mcfiduooom Hmo.oumvucoumwwflp mflucmoflmflcmflm no: mum mumuuma wEmm may an Uw3OHHOM momma CEDHOU 82 O OH Om Om Om OOH OO OH uoHumuo OH O OO ON OH ONO OO OH «Hoomse O O OO OH Om OOH Om OH cousm OH O O O OO mOm OH OH 3mzHOmm O Om Om OH OO OOH OO OH omHHcmm mm OH OH ON ON ammO OO mH mam OO OO OH O O nOmH OOH mH eHmoucoz OOH OOHuHm omTHH OHIO O uoou O O HHom mocmuusooo omamfimm Eoooa usmoumm moamfim hussoo Mom mmooumemz mucousooo ucmonmm .cmmfinoflz :H moamflm coma hub om Eoum oouw>oowu HmoooumEmc :onwHTuoouv .mmm manocmamumum mo mwfluflmcmmp cam moamuudooo .~.m manna 83 Higher population densities were generally associated with sandy soils (Table 3.2). Population densities were also higher on kidney beans, and this is related to the soil type as this variety is produced mainly on sandy soils in Bay and Montcalm counties. In Saginaw county a high population density of Pratylenchus spp. was found in one bean field where the soil was characterized as a Granby loamy sand (Table 3.3). In Bay and Montcalm counties Pratylenchus spp. were associated with both colored and navy beans, but the population densities were lower on navy beans in Bay county (Table 3.4). On a state- wide basis l3% of the 80 fields surveyed were infested with population densities > 50 Pratylenchus spp. per 3 100 cm soil plus 1.0 g root tissue (Table 3.5). Tylenchorhynchus spp. were found in all seven counties. The frequency of occurrence was lower than for Pratylenchus spp. and population densities were relatively low .(Tables 3.3-3+6). 3.2.5.3 Development of an experimental population of E. penetrans Thirty-six percent of the 100 Sanilac navy bean plants inoculated with one male and one female Praty- lenchus penetrans were infected with this nematode species and produced recoverable nematode p0pulations. .ume mason wcmEBmZTucmosum ou mcflouooom Hmo.o u my ucmHmMMHo zauCMOHMHcon no: mum uwuuwa mEmm may >3 om3oHH0m memos CESHOU OH mmH Smog cfla3mx3mx omHflcmm o no 5004 coumxooum omHHcmm o MOH Emoq cflazmxzmm omHacmw o moa Smog aocmm cfla3mx3mx omHHcmm wow mmnm Emoq mocmm waamnmmH w>m soaamw m mooa Ewoq upcmm maamnmmH muumncmuu ca nmomm Emoq hocmw maawnmmH munmncmuo ow Dome Emoq xocmm mHHmnmmH wuumncmuu o omv Emoq xocmm mHHmQMmH huumncmuu 0 wow Smog aocmm waamnmmH wmcpflx 4 O OmO EOOH socmm mHHmnmmH schHx 8 mm anON EOOH sccmm mHHwnmmH smanx O mmO amoq macaw mHHmnmmH schHx 0 Mom Ewen “mummz wocpwx om omoa Emoq umummz umummmwm o mHH Econ “mummz Hmummmmm o mmm Econ “mummz umummmmm o nova Emoq “mummz monommom o Qmomm Emoq umumoz monommmm Eamoucoz msmmflu uoou HHOm mEoooH m + aflom m mam» >umaum> wucsoo .Qmm manocxnuonocmHmy .mmm manocoawumum aflom comm .humfium> coon can mmwu HHom on coflumamu CH mmooumewc oauflmmummlucmam mo mocmuusooo m.m manna Am0.0 O OO OOOOOOOHO EHucmoHc .umce mnsmm mccE3wZIucoosum ou manouoooc newnm no: cuc Hmuumn mEcm on» wn oo30nn0m mccmE CESHOU co co Econ nmcccEnnx ocnnccm new con Econ comnwnm “cucmcmm acon co Econ nmcccEflnx Hmucwcmm ncon com Econ comnwnm umucwcmm cm cwn Econ coo>¢ kucmcmm cm co Econ nmcccEnnm kucmcmm ncon cmm Econ cownmsm Hmucwcmm co cmm Econ :mcccEwnm Hmucwcmm co co Econ sancsu kucmcwm co co Econ :mcccEnnx umucmccm noun: 0 Down Econ Hmcmnz oucnm m ncmm Econ :Hn3cx3cx hnucnccuu o co Econ hoccm oomoH huuwnccuu 5 o ncNm Econ hpccm oomoH muumnccuu 8 m comm Econ acno chmnz muumnccuu _ om co Econ moccm 3cEmmO wmcowx m Conn Econ moccm oomoH acconx o Oonm Econ xcccm annzcxzcm wmconm OH anH econ scamm aHHgmxsmx moccHx O OOH econ scHo umcmHz smacHx .c.ucoo 0 cm Econ annzcxzcx Hmncwccm hcm mammnu uoou nnOm mEooon m + nnOm mEooon max» >umnuc> hucsoo .mmm masocmnuonoccnxe .mmm manocmnmucum nnom ccmm .U.ucoo m.m mHQcB .ummB mnsox mccEBmZTucmosum ou monouoooc “mo.o u my ucouowmno unacconmnconm no: mac Hmupmn mEcm wnu wn @030nnow mccmE CEDHOU co com = ocnnccm cm com = ocnnccm co cmn : ocnnccm co chm : Houcmcmm co con : ucucmcmm con cmm : nwucwcwm cm con : umucucom con co : uwucmcmm cmn cmm = Houcmccm co ammn oz Hmucmcmm cnoomse co co Econ unconmlccOHm ocnnccm mO mO Econ smHo muHHm suHumno omancm co co Econ wcnu xunnm occcucm ocnnccm co co Econ cc0nm ocnnccm % co co Econ nmcccEnnxlnnnnxucm ocnnccm con co Econ anncxucmlocmcu ocnnccm con co Econ nnnnxucm w Econ mcno mEnm umucmcom co nmmm occm mEcon anccuw umucmccm Econ woccm con co mafia >um> 0HQ3H& Hmucmcwm co co Econ Mcnu Hocmnz uwucmcwm scanmcm momma» uoou nnom mEooon m + nnOm mEooon waxy muwnuc> hucsou .Qmm monocwmuonocmnme .mmm monocwnaucum anom ccmm .p.uc00 m.m mHQcB AmO.O u OO OOOOOMOHO sHucmoHchmHm omcHEumumo .pmme mnsox mccEBwZTucmosum on uoc muc uwupon mEcm can an om30nn0m mccmE CESHOU wcnomoooc co com Eocn koacm cuOEumz UOHucHU con con Econ occm mocnucmxomum wcconx co co Econ ocmco acconx cm ncom Econ annnxucm ucucmcmm w ocnnccm con acov Econ annnxucm ocnnccm con co Econ wcno wmsccwm ocnnccm co cmn occw >Econ moonuncm ocnnccm cm 3mm Econ annnxncm ocnnccm cm con Econ nannxucm ocnnccm con co Econ nnwaxucm ocnnccm acnucuo 7 cm com a ocnnccm 8 co co .. ocnnccm con co : ocnnccm co com z ocnnccm can cmn = Hmucmcom co cmn : Hmucmcmm co co = umucmcmm co co .. umucmcmm cmn cmm = Houcmcom co co oz Houcmcmm ocnwccm momma» poou HHom mEoooH m + nflOm max» >umwuc> wuczoo .Qmm monoc>SHonocmn>B .mmm monoconwucum nnom ccmm .©.uEOU m.m manB 88 Om Om OH O OH OOH OO OH mam mammn cmuoHoo Om om OH OH O mOH OOH OH EHmoucoz mecca cmuoHoo O O Om OO ON O OO m mam mccmn >>mz OO Om OO O O OOH OOH m eHmoucoz mammn m>mz uoou m + con oowwwwnumwmnn cwwmw o . mEooom wocmuucooo omnmEcm hucsou camp 0 u m \mccuumcwm .m usoouom monmnm ccom mccmn UGHOnoo occ >>cc nunz omucnUOmchmoooucEm: conmonluoonv .mmnucsoo Encoucoz occ wcm mm .mmm manocmnmucum .v.m mnnce 89 H.mmm manocwuonocmnwav o o N.nn m.mm o.mm me m mooucEw: ucsum m.OH m.NH m.O~ ~.HH m.Hm OO mm A.amm manocmHsumumO cooucEmc COnmonluoom noon m HOm EU OOH OOHTHm omnHHTTOHJH, O mocmuusooo + H. m OOH monounsooo unmoumm usooumm Mom mmCOchmz mooucEmz .OOOH cH cmOHEOHz EH mononm :cwn xuo om Eonw omuo>oomu monoucEwc Ununmcucmnuccnm mo oocwuusooo .m.m oHQcB .umme mnswm mccE3m21ucoosum on» on mcncuoooc Amo.o n my acoummmno unacconmncmnm no: muc mucuuwn oEcm on» an omsonnom mcccE cEsnou o c on om om cm on on uOnucHo o c on ow om cm cm on cnoomza mu, o o on m ov cv ow on consm o o o om om cm cm on Bchmcm o o om om om cm ow on ocnwccm o o mn mm om cm ov mn mcm o c on mn we cm mm mn Encoucoz oon oonlnm omnnn onlnn o noon m + nnOm mocmuusooo mEooon mom cocouusooo ocnmEcm aucsoo unwouom mmcoucEmz usmouom mononm .mnmn cmeonwnw ccmn who ccmnnonz om Eoum omuo>oomu AccoucEwc ucsumv.mdm manocxnuonoccnwa mo hunmcmo GOnucnsmom occ mocmuusooo m.m cnnce 91 The total population densities in soil and roots asso- ciated with navy bean plants varied considerably (Figure 3.22). The symbols above the X axis represent plants infected with g. penetrans, while the large proportion of symbols on the X axis represents non- infected plants. The highest population density was 250 P. penetrans per 100 cm3 soil plus 1.0 g root tissue (Figure 3.22). 3.2.5.4 Identification of the life cycle stages of_§ . penetrans Four morphometric characters were significantly different (P = 0.05) among the five stages of P. penetrans which were studied (Figure 3.23). Considerable variation in body length of females from the experimental population was recorded. The mean length of a female was 566.3 pm with a standard deviation of 55.8 um (Table 3.7). Differ- ences in body width were significant (P = 0.05), (Table 3.8). Oesophagus length and stylet length were also significantly different (P = 0.05) among stages, but the range in values for all stages was relatively narrow (84.8-137.0 pm) for oesophagus length and (10.2-17.3 pm) for stylet length (Table 3.7). Significant differences in allometric characters were observed among stages 92 300 1 1 250 1 1 200 1 POPULRTION DENSITY 1§0 Figure 3.22. 20 40 60 80 100 N0 . 0F PLIRNTA —— Total soil and root population densities of Pratylenchus penetrans associated with navy beans exposed to an initial density of one female and one male g. penetrans. 93 ////////////////////// ///// %///////////////////////////%nm %///////////////%.a omas S cters and bi of Pratylenchus penetrans. chara 3.23. Morphometric Figure ages t1]. cycle 5 Ver fidence nt 95 % con represe bars rva s. tica inte 94 H.O 0.0 m.O HOV H>oO O.Hm O.OH O.OH Aomc m.mmm m.Om~ O.HON EOOEOH mum>o O.OH H.O H.~H 0.0 O.O AOO A>oO O.m O.H O.~ 0.0 0.0 lamv H.Om O.Om O.m~ O.mH 0.0H sumcmH HHme ~.O H.m H.m O.m m.mH HOV A>oO O.H O.O m.O 0.0 O.H Homc m.OH O.mH O.mH O.mH ~.OH :umcmH ummHum m.O 0.0 O.m N.m 0.0 AOO O>oO O.O O.m N.O O.O H.O Aomc O.OmH O.ONH H.m~H O.mHH O.OO EOOEOH mammnm0mmo O.OH m.O 0.0 H.O O.O HOV A>ov N.O O.H O.O 0.0 0.0 Aomv O.Om m.OH O.mH O.mH O.HH nucHz scom 0.0 O.~H O.O N.O m.O HOV AOUO O.mm O.~m O.ON 0.0m O.OH Aomc m.OOm O.OMO N.OOO O.Omm m.mmH EOOOOH scom onuuchnmuoz mHmemm mHmz O m m a» on U: Hmuocucsu cwcum onoho cmnn .mccmn >>cc nun3 coucHUOmmc mccupocwm manoconmucum wo mwmcum mno>o omnn on» NO mumuocncno owHumEoanoz >.m onnce .ummu mnsmm :cE3mz ucmosum may on mcncnoooc Hmo.o n my usmummmno anucconmncmnm uoc mac umuumn mEcm mnu wn om30nn0m mccmE CEDHOU m“ om.mmm OH.Om cm.OH OO.OmH OO.O~ cm.OOm mmHmEmm uHscm o0.0~ oO.mH O0.0~H cm.OH OO.OOO mmHmz uHscc nm.Om~ OO.MN. oO.mH OH.m~H oO.mH o~.OOO OOO mO.HO~ nO.mH nO.mH nO.mHH nO.mH n0.0mm cum .111 mO.OH mm.OH O.OO m O.~H mm.mOH cam numcmn sumcmn numcmn numcmn nucHz apocmn mwcum mum>o HHmO umHmum msmcsmommo mcom acom “mHomo mmHn .mmmcum mnomo mmnn mccuumcmm msnocmnmucum mo mumuocucno unnumEonmuoz m.mumnnc9 96 (Table 3.9-3.10). 3.2.6 Discussion The study of the field distribution of Pratylenchus penetrans indicated that an aggregate-type distribution approximating a negative binomial type distribution was characteristic for the distribution of P. penetrans in the field. The nature and distribution of nematodes in the field is of great importance in determining sampling pattern, and number of replicates to use in experimental procedures. The nature of statistical analysis and transformations which should be applied to data are also to some extent dependent on the nature of the distribution of the pest (Beall, 1941; Kleczkowski, 1955; Wayman, 1959; Hayman and Lowe, 1961; Taylor, 1961; Kendall, 1948; Elliott, 1973). Logarithmic transformations involving coding of data containing zero values are useful in analysing nematode data (Wallace, 1973; Barker and Nusbaum, 1971). The number of samples which should be taken is dependent on the degree of precision desired and this in turn is limited by the relative economics involved. The results from the nematode distribution study indicated that large variations are encountered in sampling nematode populations in the field. Use of small numbers of samples 97 . EOOEOH HHmu \nuOEOH moom u m ooo oon x on numcmn msmcnmommo \numcmn zoom u N numcoH moon x anon: woom n O noon: Ecom\sum:OH zoom n H m.vm mm.mn mm.mn no.vn mv.mm Hwy H>Uv mon.o Ono.o moo.o moo.o voo.o Homv mnm.o von.o moo.o mmo.o mno.o Hwy mmchnm v m.mn n.m m.nn v.5 m.m va H>UV m.N m.n N.~ m.n O.H Homv ~.mn o.nn m.mn v.nm m.>n manc> o m o.m n.on v.m m.nn m.m Hwy H>UV v.o m.o m.o v.0 m.o Hamv n.v H.m m.m m.~ m.m mmsnc> a N m.~n m.mn v.n m.m m.on va H>Uv ¢.m N.¢ n.~ ~.~ >.n Homv m.mn h.mm m.mm >.vm m.on manc> c n unnumE0nn< mmncEmm mmncz cue cum cam umuocucnu mwcum mnoko mwnn .mccmn >>cc £un3 omucnoommc mccuumcmm manocmnhucum mo mmmcum mnowo mmnn ms» wo mumuocucno onHumEonnn m.m mnnca 98 ooo.oon x ma nooooH soon x noon; scomm nooooH Hnou\nuoooH scomO suocmn msmcnmomm0\numcmn moomm unmmnz hoon\:umcmn moomm .ummu mnsmm ccE3mz unmosum man on manouoooc Hmo.o u my ucmummmno mnucconmncmnm uoc mnc nmuumn mEcm mnu an omSOHHOM mccmE CESHOU H Ummm.o QN.mn UH.¢ Qm.mH mchEmm UHDG< Dvoa.o cw.hH U¢.m Uh.NN mchE unsp¢ ammo.o Qcm.mH Uw.m mmm.mm nae OOOO.O oOO.H~ nO.~ OO.O~ cum cmno.o Qcm.ha cm.N cm.mn GEN mosv mmcEOnm cmsnc> =0: nmsnc> zm: Nm5nc> =c= mmcpm 1 Hmuocucno unnumEofiflfl .mmmcum mnoxo mwnn mcmuumcmm monocmnhucum mo mumuocncno owuumEOHHM cw mmocmummwno .on.m mnnce 99 in experimental procedures could therefore lead to inaccuracies. The most desirable procedure is to take large numbers of samples usually greater than 50 (Langdon, 1963; Elliott, 1973; Goodell, 1978). Unfortunately while large sample numbers ensure relatively accurate biological information, there are disadvantages associated with time and cost. involved in taking and processing large numbers of samples. Therefore a compromise must be made between statistical accuracy, labor and cost to determine the optimum sample size. First it is necessary to determine the degree of experimental error which can be tolerated and still retain a substantial amount of accuracy. The percent error can be expressed as the standard error of the mean (S.E.). The ratio of the standard error to the mean (S.E./ i) represents an index of precision (D) (Elliott, 1973). The calculation of the index varies depending on the nature of the distribution, i.e. whether normal, poisson or aggregated (negative binomial). For the normal or random distribution the index of precision is calculated as: 100 D = S.E_ _ x / x 2 D=%§. x n and the number of samples which should be taken is calculated from this equation as: For a poisson type distribution the index of precision is calculated as: D II xlha : DH and the number of samples which should be taken is calculated as: § 1“: 02§2 The calculation of the index of precision for an aggre- gate type distribution approximating a negative binomial distribution involves calculation of the parameter K which is an index of dispersion (Elliott, 1973). Various methods for calculation of K can be employed (Elliott, 1973). The choice of method is to some extent dependent on the mean values, number of samples and degree of aggregation. With a calculated K value the index of 101 precision for a negative binomial distribution can be calculated as: and the number of samples which should be taken is calculated as: D 5': K For example if a standard error of the mean equal to 20% can be tolerated then D = 0.2 and 0.2 13.98 1.63 n = 17 for the sample size which should be taken for sample level A of Table 3.1 where the mean value was 13.98 and K was 1.63. In this analysis K was calculated according to the moment method (Elliott, 1973) from the equation: 102 where § is the arithmetic mean and 32 is the variance of the sample. In this study a sample size of 184 was employed for estimating the mean value of the population of P. penetrans in the field for this sample level. Calculations indicate that allowing for a standard error of 20% of the mean, a sample size of 17 could be employed. The sample size would however increase as the degree of precision is increased. For example if a standard error of only 5% of the mean could be tolerated then D = 0.05 and _ l ( 1 + l ) n" 2 0.05 13.98 1.63 n = 308 Therefore to obtain a precision of a 5% error the optimum sample size is 308. This is larger than the sample size employed. The relative cost of taking and processing these samples however limited the sample size to 184. 103 Calculation of a desirable sample size based on the degree of error which can be tolerated is valuable however for initial decisions on choice of sample size. Experimental procedures for the survey of 80 bean fields in Michigan involved collecting two samples of six soil cores from one hectare size areas within bean fields. With this sampling procedure Pratylenchus spp. were found in 68% of the fields and Tylenchorhynchus spp. were present in.45% of the 80 fields. The results of the study on field distribution of Pratylenchus penetrans indicated that nematodes are generally found in an aggregated-type distribution in the field, and therefore detection of nematodes through use of random sampling procedures should involve use of large sample sizes. However the economic and time factors involved in con- ducting this survey limited the sample size to two replicates. This allowed for only one degree of freedom in analysis of variance, and large within field variances were obtained resulting in a few significant differences (P = 0.05) among population densities within a field (Table 3.3). The absence of plant parasitic nematodes in some fields could be related to the inability to detect populations from an aggregate-type distribution with the use of random sampling procedures. 104 The results, however, indicated the presence of plant parasitic nematodes in bean fields and can be viewed as an "alert", which should not be neglected. The highest population densities were generally asso- ciated with sandy soils. This is expected and in agreement with report findings on relationships between nematode population densities and soil types (Oostenbrink, 1966; Norton, 1978). Information from this survey can be useful in conjunction with information on economic thresholds of P. penetrans. The population densities in fields in different counties together with an economic threshold density could be used to estimate economic losses due to this nematode species in dry bean production in the counties examined. The data though useful has its limitations in that the observed densities are related to a particular time of the season and may be higher or lower at other periods. The dynamic nature of the nematode species must also be considered in estimating losses. The data provides a basis for thought for research on interactions of Pratylenchus spp. and dry beans. The development of an experimental population of P. penetrans was necessary to ensure that individuals 105 used in preparing inoculum densities for research experiments were obtained from similar genetic source and should be typical of one race of this species. The population densities obtained at the time of sampling is no indication of the maximum reproductive potential of this species on beans. The length of the life cycle varies depending on the temperature and the associated host crOp. The absence of populations associated with 64% of the 100 bean plants could be due to the high mortality, detection procedure ineffi- ciency (Kotcon, 1979), or to the life cycle stage at the time of sampling. Nematodes could have been present in the egg stage or first stage larvae within the eggs and samples were not processed for detection of these stages. The presence of P. penetrans on 36% of the bean plants indicated that these nematodes were able to survive, move towards susceptible roots, penetrate, feed and reproduce within these roots. While some of the females may have been fertilized before inoculation, males were added to increase the likelihood of fertil- ization. Morphometric characters of nematodes are influ- enced to a large extent by the environmental conditions of moisture, temperature and also the host crOp. Tarte 106 and Mai (1976) observed considerable variation in morphometric characters of E. penetrans developed on alfalfa callus tissue. Comparison of morphometric characters of the population of P. penetrans developed on Sanilac navy beans in culture boxes in the green- house at a temperature of 77 i 10 C with the original population of P. penetrans described by Sher and Allen (1953) and Loof (1960) indicated some differences. The mean length,fla" value and "b" value for the female described by these taxonomists were 530 um, 26 and 5.8 respectively, while values of 566 um, 19.5 and 4.1 were obtained for similar morphometric and allometric characters of the female from the population developed for research experiments in the greenhouse. Although differences in body width were statis- tically significant (P = 0.05), identification of life cycle stages through use of this morphometric character is not feasible because of the narrow range in values and small size involved. The narrow range in values obtained for oesophagus and stylet lengths respectively limit the usefulness of these characters for identification of stages. Because of the significant differences and wide ranges in values for body length, ovary length, biomass, "a" value, "b" value and "c" value these 107 morphometric and allometric characters were used to develop a key to the life cycle stages of Pratylenchus penetrans (Table 3.11). The egg and first stage larvae were not easily recovered and can be readily identified if found. These two stages were not included in the key because they were not extracted and enumerated in the sampling procedures. 108 Table 3.11 Key to the life cycle stages of Pratylenchus penetrans Spicules absent, body length l93.3-566.3 um . . . 2 Spicules present, body length, 4378'* 52.7 um biomass, 0.104 f 0.017 pg, "a" value, 22.7 i 4.2 . . . . . . . . . . . . . . . . . . . . . Adult males Body length, 193.3 : 9.5 ug, ovary not visible, biomass, 0.018 t 0.001 ug, ”a" value, 16.2 i 1.7, "b" value 2.3 i 0.2, vulva notconspicuous . . . . . . . . . . . . . . . . . . Second-stage juveniles Ovary present, body length greater than 193.3 : 9.5 Tun . . . . . . . . . . . . . . . . . . . . . 3 Ovary length, 201.8 f 14.6 pm "a" value, 24.7 i 2.2, "b" value, 2.9 i 0.4, ovary slightly conspicuous . . . . . . . Third-stage juveniles Body length greater than 334.4 1 30.6 um, vulva highly conspicuous, ovary well-developed . . . 4 H- Body length, 440.2 1 28.9 um, ovary length, 258.5 H- 18 um, biomass, 0.065 t 0.008 ug, "a" value, 28.6 2.1 . . . . . . . . . . . . Fourth—stage juveniles Body length, 566.3 1 55.8 um, ovary length, 352.5 i 21.6 um, vulva highly conspicuous, ovary well- developed, spermatheca present, "a" value, 19.5 i 2.4, "b" value, 4.1 i 0.4, "c" value, 19.2 1 2.6, biomass, 0.316 1 0.108 pg . . . . . Adult female 109 3.3 Pest-crop Interactions 3.3.1 Pathogenicity A survey on the incidence of nematodes in dry bean production in Michigan indicated that root-lesion nematodes (Pratylenchus spp.) were present in bean fields and P. penetrans was the most predominant plant parasitic nematode species encountered. The objective of this study was to evaluate the pathogenicity of Pratylenchus penetrans on dry beans. 3.3.1.1 Method The experiment involved a completely randomized design of six replicates of six treatments including population densities of 0, 25, 50, 100, 150 and 300 3. penetrans per 100 cm3 soil. Thirty-six 4.72 cm clay pots were filled with 3000 cm3 sandy clay loam soil con- taining the desired densities which were obtained by mixing steam sterilized sandy clay loam soil with P. penetrans infested soil from culture boxes in the greenhouse. Three navy bean seeds cv Sanilac were planted in the soil in each pot. Plants were thinned out two days after germination leaving one seedling in each pot. The plants were watered daily and maintained at 80 t 10 C in the greenhouse for a period of 95 days. Plant height, leaf area, shoot fresh weight, root weight, root length 110 and dry bean yield were recorded after this growth period. Shoot systems were oven dried at 30 i 5 C and shoot dry weight was recorded. Soil and root samples were taken for nematode analyses (3.1.1.2 and 3.1.2.2). g. penetrans were extracted and enumerated (3.1.3-3.1.4). 3.3.2 Susceptibility of six navy bean varieties to Pratylenchus penetrans Because of genetic variability the response to infection by plant parasitic nematodes may vary among cultivars of plant species. The discovery of nematode resistant or tolerant bean varieties is important for development of nematode control practices in dry bean production. This study was designed to determine the effect of P. penetrans on six navy bean cultivars. 3.3.2.1 Method The experiment involved a completely randomized design of three replicates of six bean varieties. One hundred and twenty-six 2.36 cm clay pots were filled with 1000 cm3 noninfested P. penetrans steam sterilized sandy clay loam soil, and 126 similar clay pots were filled with 1000 cm3 sandy clay loam soil containing densities of 150 P. penetrans per MMN)cm3 soil respectively. The desired densities were obtained by mixing steam sterilized 111 sandy clay loam soil with appropriate quantities of 3. penetrans infested soil obtained from culture boxes. Three navy bean seeds of each variety - Sanilac, Seafarer, Gratiot, Saginaw, Kentwood and Tuscola respectively were planted in the soil in each pot. Plants were thinned out two days after germination leaving one seedling in the soil in each pot. Plants were watered daily and maintained at 75 i 10 C in the greenhouse for a period of 108 days. Plant height, shoot dry weight, leaf area and yield were recorded at seven intervals during this growth period. Relative growth rates were calculated (3.1.8). Soil and root samples were taken for nematode analyses (3.1.1.2 and 3.1.2.2) and g. penetrans were extracted and enumerated (3.1.3—3.1.4). 3.3.3 Responses of Sanilac navy beans to infection with different initial population densities of Pratylenchus penetrans Plants are subject to inherent ontogenic drifts, and responses to pests and diseases vary at different stages in the growth and development of plants. The objective of this study was to examine the responses of navy bean plants to infection with varying densities of g. penetrans at different periods during the growth and development of these plants, and to examine the population 112 dynamics of P. penetrans associated with navy beans. 3.3.3.1 Method The experiment consisted of four replicates of eight treatments including population densities of 0, 5, 10, 20, 4o, 80, 160 and 320 g. penetrans per 100 om3 soil. Three hundred and eight 2.36 cm clay pots were filled with 1000 cm3 steam sterilized sandy clay loam soil. 3. penetrans were extracted from roots of navy bean plants removed from culture boxes in the greenhouse and a suspension containing a calculated density of P. penetrans was prepared. The desired densities for this experiment were then added to the soil in respective pots. Forty-four 2.36 cm clay pots were filled with steam sterilized sandy clay loam soil to serve as controls. Three navy bean seeds cv Sanilac were planted in the soil in each pot. Plants were thinned out two days after germination leaving one seedling in the soil in each pot. Plants were watered daily and maintained at 80 i 10 C in the greenhouse for a period of 95 days. Plant height, leaf area, shoot fresh weight and root weight of plants were recorded at 10 intervals during the growth period. Shoot systems were oven dried at 30 i 5 C and shoot dry weight was recorded. Dry bean yield was taken at the end of the 95 day 113 growth period. Soil and root samples were taken at 11 intervals (3.1.1.2 and 3.1.2.2) and P. penetrans were extracted and enumerated (3.1.3-3.1.4). Data on shoot dry weight were used to calculate the relative growth rates of plants (3.1.8). Initial nematode mortality was calculated for each initial density of P, penetrans. Sampling dates were converted to accumulated degree days (3.1.7). 3.3.4 Results 3.3.4.1 Pathogenicity Final root and soil population densities of g. penetrans were significantly (P = 0.05) higher than initial pOpulation densities (Figure 3.24). Regression of the log of the final root pOpulation densities on log of the initial population densities of g. penetrans indicated a significant linear correlation and the equation for the relationship is: log Y 0.10 + 0.99 (log X) R = 0.99 where Y = log of final densities of g. penetrans plus one and X = log of initial densities of P. penetrans plus one. The regression line for this relationship indicated that population densities in navy bean roots increased with increase in initial soil population densities of 114 O D 3 8“ In §4 A _’ B 3 CO O (00" U) T " "' 1: I}: u U 8. o o N o O 0-‘ "‘ \ \ .. _ mu— ”8. 0.90 o1.04(L00 x1 R : 0.99 v v v a fi 1 T T 1 ‘0 100 200 300 400 1 ,0 100 1000 H / 100 cm SOIL 81/ 100 CH3SOIL D O :1 8- c 3 g C 11 1—34 F— o g "‘ 8 22* m 01 t5 0 x \ O ‘2‘ F m 9_ L00 Y : 0.10 . 0.99 (L00 x1 3‘ / a = 0.99 % V 100 V 230 w 300 v 400 1 (o 1:30 1000 P. l 100 CH SOIL P1 / 100 CH’ SOIL Figure 3.24. Influence of initial soil population densities of P. penetrans on final soil population densities (A & B), and final root population densities (C & D) of g. penetrans associated with navy beans. Vertical bars represent 95 % confidence intervals. 115 P. penetrans (Figure 3.24D). Final soil population densities increased with increase in initial soil population densities (Figure 3.24C). Regression of the log of initial soil densities on soil final densities of P. penetrans indicated a significant linear relationship with a high correlation coefficient value (R = 0.99) (Figure 3.24B). The equation for the relationship is: Log Y = 0.90 + 1.04 (log X) R = 0.99 where Y = log of final densities of P. penetrans plus one and X = log of initial densities of g. penetrans plus one. The growth and yield of plants exposed to initial soil densities of 50, 100, 150 and 300 g. penetrans per 100 cm3 soil were significantly (P = 0.05) lower than that of noninfected plants exposed to an initial soil density of 0 P. penetrans (Figures 3.25-3.27). At the time of harvest the initial density of 25 P. penetrans per 100 cm3 soil had no significant (P = 0.05) effect on plant height, shoot fresh weight, leaf area and root length. Shoot dry weight was significantly (P = 0.05) decreased by this density while root weight and root length were significantly (P = 0.05) increased by 25 B. penetrans per 100 cm3 soil (Figure 3.26BJ2&1M. 116 .muccnm :cmn w>cc mo Hmv unmnmn occ Adv cmuc mcmn co mccuumcmm .m mo mmnunmcmo COHOcHDQom ncnuncw ucmummmno mo mocmsnmcn .mm.m ousOHm oov Onowmzu OOH \ com com m OOE mo 1H013H 1N87d (N3) oov Onowmzu OOH \ m OOm OON OOz O0 f .m 7v 10 8 OD < . m S 6388 3631 GNU] 117 at: :91 m '2 ..‘ w A m A C: N B 3 i \ .— A O .1 (D 04 g. HN B e 1 3 . 5 "2: I n H .. 8 § 1 E >94 6- “4 g d 8 ‘ r- 1 U) “-1 g 0‘ 1 W T c3 ‘0 V 100 V 200 300 400 91 100 200 300 400 n / 100 CHBSUIL a / 100 cm SOIL .1 ST 1 C D 4 A ")4 .— ‘n " 0 5 *- 1: 5 :— ... J g 01 N O! ‘i‘ 3 1 '5 :3 o o C J a: 4 .- ID ‘0 150 260 a 360 a 400 ‘0 f 100 - 200 V 300 400 a / 100 cm3 80L; 1: l 100 0135011. Figure 3.26. Effect of different initial population densities of P. penetrans on shoot fresh weight (A), shoot dry weight (B), root weight (C), and root length (D) of navy beans . Vertical bars represent 95 % confidence inter- vals. 118 YIELD/PLRNT 100 ' 200 3 ' 300 400 R / 100 CM SOIL Figure 3.27. Effect of different initial population densities of P. penetrans on navy bean yield. Vertical bars represent 95 % confidence intervals. 119 3.3.4.2 Susceptibility of six navy bean varieties to Pratylenchus penetrans g. penetrans were recovered from roots of all six bean varieties. Higher total root and soil densities of g. penetrans were associated with Sanilac, Seafarer and Tuscola varieties compared to Gratiot, Saginaw and Kentwood varieties (Figure 3.28). Three maxima in population densities were evident at 357, 927 and 1132 DD 10 C respectively on Sanilac, Seafarer and Tuscola varieties. Population densities associated with Gratiot and Kentwood varieties initially decreased until 340 DD 10 C and then steadily increased reaching maxima 785 DD 10 C (Figure 3.28). This was followed by another decrease at 927 DD 10 C and then an increase at the end of the growth period (Figure 3.28). Plant heights were significantly lower for B. penetrans infected plants of Sanilac, Seafarer and Tuscola bean varieties (Figure 3.29A-C; Table A1). Plant heights increased with increase in degree days reaching a plateau atlllo DD 10 C (Figure 3.29). The difference in response to infection by P. penetrans is evident from the equations for the relationship. For noninfected Tuscola plants the equation for plant height is: Y = 36.79 - 6152/X (R2 = 0.99) 120 8- x anIan [D ... m SERFRRER g « A TUSCOLR 0: D o GRRTIOT c5 3— x 5901an + .1 J a KENTHOOD C3 03 c: n O- m P .PENETRRNS/IOO CM 1 ' r T r 0 360 680 980 BCCUMULRTED DEGREE oan (DDch V T T I 1 1200 Figure 3.28. Population dynamics of P. penetrans associated with six navy bean varieties. 121 Figure 3.29. Influence of P. penetrans on height of six navy bean varieties over the growth period. 122 .Om.m OHOOHO .. Son: 2% uwzomE 8:. .2225... 1 Eco fl wEo 3.83 out. ...:......a . OOO OOO OOH OOO. 8... OH DOW p P » 9U r b mm 0mm OnU . . O T1 d 11 .H 0 HT 0 .H U W I W m 1 1 H H H 3 m 3 a z 3 I T '1 I0 I 0. 0 my I H H I. J I. M. O m m .m m. -m w .3... u... H \ .nno . TS u > 3.3.5.-.. I 3... ".... x \ n... - 2.8 u » SSE... I .3... u.... x \ SN. . 5.3 u > 3.3.2..-. 1 .8... 1.... x \ SS - ..c... u .. 35......2...‘ n. on... J... .. \ nu... - 8.9.. u .. 3.3.2.22. I n. 2...... ".5 x \ m2. - 223 n » 5532.521 afi ' ' ’ 8...:sz -... 10 8:5... -... 0 5.2.9.... - a o 329.: fan mumouo SEEECLQ H... 29.: fan umzomc 85:52.2". H. San. w>¢o umxomo 33:22:... O . O O O OO . .... ...... ..Om cum. 2.... .....O 2.; cu OW Ow ... .m 00 OOW .... . . p0 ..1 d .1 ... -1 d 0 ..I 0 1| 0 «I. U U Hy N N N 1 I. 1 mm. m... H .76. T .m 1 .m u 0 0 0 H H H I. l I. m m m 10 1 T0 :5 TO I. .8... u... .. \ man - ....O. u .. 8.3.17: - .3... J... .. 4 $8 - 2.2 u p 28......1 .. .5... u.... .. \ an... - 3.... u » 3.3.12.1: ... u T . u Ill 8 . u I . u 1' .3... -..: x \ On; 2 an .. 3.3....sz v .3... J... x \ «.2 - .....z u .. 3.8.2.621. n. v .3 O .... .. \ 39 .n on .. 3.8.5.5.. n. v .383. .5 -0 5.3.38 - z . o ......zcm -... O 123 where Y = plant height and X = accumulated degree days at base 10 C. For E. penetrans infected Tuscola plants, however, the equation for the relationship is: Y = 19.17 - 3015/x (R2 = 0.98) The comparison of the two equations show that plant heights were lower in P. penetrans infected plants. For g. penetrans infected Gratiot plants the relationship between plant height and accumulated degree days is: Y = 26.36 - 4268/X (R2 = 0.99) and for noninfected Gratiot plants the equation for the relationship is: Y = 26.15 - 4113/x (R2 = 0.98) Comparison of these two equations show that heights of Gratiot plants were not significantly influenced by g. penetrans. The relationship between root weight and accumulated degree days correlated well with a second degree polynomial type relationship as expressed by the curves in Figure 3.30A-F. Root weight increased to maxima at 750 DD 10 C and then decreased rapidly until 1088 DD 10 C (Figure 3.30). Root weights of Sanilac, Seafarer and Kentwood varieties were significantly lower (P = 0.05) in E. penetrans in- fected plants compared to those of noninfected plants, while for Gratiot, Saginaw and Kentwood varieties there 124 Figure 3.30. Influence of P. penetrans on root weight of six navy bean varieties over the growth period. Equations for the relationships between root weight and accumulated degree days at base 10 C. Y = root weight ; X = accumulated degree days. NI = noninfected ; I = P. penetrans infected cv- Sanilac NI: Y = - 2.76317835468 + 0.0213472540522x - 0.000001659285771 x2 (R = 0.92) 1. Y = - 0.93304277061 + 0.009244466174 7 x - 0.000007408234021 x2 (R = 0.86) cv- Seafarer NI: Y = - 2.84413943365 + 020219605136831 x - 0.0000170987044 x (R = 0.87) I Y = - 0.810740336604 + 0.00841788236 24 x - 0.000006740109478 x2 (R = 0.87) cv- Tuscola NI: Y = - 2.92376327034 + 0.023442906419 x — 0.00001790035985 x2 (R = 0.92) I Y = - 0.87282288469 + 02009815010610 3 x - 0.0000078876075 x (R = 0.87) cv- Saginaw NI: Y = - 2.39974783238 + 0.9196105924317 x - 0.00001514828469 x (R2 = 0.96) I Y = - 2.44222442166 + 0.819942046743 x . - 0.00001556483007 x (R = 0.97) cv- Gratiot NI: Y = -2.33094449815 + 0.0 9195936554 § - 0.00001478955799 x (R = 0.90) I Y = - 1.99770667355 + 0.318337895437 x - 0.00001444678826 x (R = 0.90) cv- Kentwood NI: Y = - 2.8314348122 + 0.05507583198542x - 0.00001946861258 x (R = 0.87) I: Y = - 2.65487564121 +_O.924157245640§ X (R= 0.00001882603424 X 0.89) I .Om.m ouomHO 1 Sec. 3.3 “Exams out. _._:......a 152: mrcc umzomo awnafitzuua 125 .... OOO. 8.. cow 8.. OOW. 2.... OH. OOW. Om... 2.... .n . . . . no N. H. u... 0 0 D I 0 .. I I O m l. . v I. H ... H .m. H ... 3 I 0 m u .zm l I. U I. a m o c 0 / / v / d . w u T .l .I 1 a U W ..v M N a I I. m U m I. Q a U 83...... ....- BZE... ....- SSOOEzoz ..l- 88:...sz I ..s 8...:sz -5 2...:ch -5 8:5... -5 H... San. was “among SEE—=77... 1 Soc. 2% mumouo out. 522...... 1 Eco. wEn unmoun Snazizcuc O OOm . OO O O OON... O...m O...O 8W. 2.; 0.0 . OOW .O O... mm P. l 8 M. .. w 0 O .. 0 0 I 0 I. I. Y I. NH H 4...”. B 3 .... .6. .2 O l l I. m 0 ... .... / / v I d ... d HI .I n O. .... U ' N N 1 N 1 I. .1 a 8.5.... I.-. a 8.8.... I..- BSEEzOz I 8.3....sz I SEE!!! II... T: OOOEOOO -5 OOH—zen -5 «Joumah -5 ‘1 126 were no significant (P = 0.05) differences in root weight of noninfected and g. penetrans infected plants (Figure 3.30; Table A2). Leaf area of Sanilac, Seafarer and Tuscola plants were significantly (P = 0.05) decreased by P. penetrans while differences in leaf area in noninfected and P. penetrans infected Saginaw, Gratiot and Kentwood varieties were less marked (Table A3). Dry bean yield from Sanilac, Seafarer and Tuscola varieties were significantly (P = 0.05) lower in g. penetrans infected plants than in noninfected plants (Figure 3.31). For Gratiot, Saginaw and Kentwood varieties there were no significant (P = 0.05) differences in dry bean yield in g. penetrans infected and noninfected plants (Figure 3.31). For the varieties Sanilac, Seafarer and Tuscola the relative growth rates of g. penetrans infected plants were lower than those of noninfected plants (Figure 3.32A, B, C). For Sanilac plants, relative growth rate was higher in noninfected plants throughout the growth period (Figure 3.32A), while growth rate of noninfected plants of Seafarer and Tuscola varieties were higher than that of P. penetrans infected plants from initial growth up to 930 DD 10 C, after which there was no difference in 127 7 I— m. / g: 6‘) g a: - g / \\ cud _ a? : 7 —~ 7 7 D 96.3 Es?- (us? '66:: £66 {£63 VRRIETY Figure 3.31. Effect of P. penetrans on yield of six navy bean varieties. Vertical bars represent 95 % confidence intervals. N = noninfected ; I = P. penetrans infected San = Sanilac, Sef = Seafarer, Tus = Tuscola Gra = Gratiot, Sag = Saginaw, Ken = Kentwood. 128 Figure 3.32. Effect of P. penetrans on relative growth rate of six navy bean varieties over the growth period. Equations for the relationships between relative growth and accumulated degree days at base 10 C. Y = relative growth rate per week ; X = accumulated degree days. NI = noninfected ; I = P. penetrans infected cv— Sanilac NI: Y = 0.0755662541602 + 0.0909430491099 X2 0.000001340226071 X (R2 = 0.89) I: Y = 0.0575269502686 + 0.081084197987 7 X 0.000001352304453 X (R = 0.92) cv- Seafarer NI: Y = 0.0789468044517 + 0.0009585056413 X - 0.000001357854103 x2 (R = 0.85) I: Y = 0.02323289969 + 0.0003318011136 - 0.000001231264458 x (R = 0.85) cv- Tuscola NI: Y = 0.0705445316036 + 0.0909825407043 x - 0.000001353147372 x (R = 0.78) I Y = 0.0026517726648 + 0.00104944243792 x - 0.0000013249396614 x (R = 0.86) cv- Saginaw NI: Y = 0 .0640298556787 + 0.0810262552332 X 0.000001387527968 X (R = 0.80) I: Y = 0.0708459814593 + 0.00100470707038 x - 0.000001391798334 x2 (R = 0.79) cv- Gratiot NI: Y = 0.0800559470947 + 0.091014915726 5 X - 0.000001412741105 X (R = 0.85) I: Y = 0.080009763156 + 0.0099800761301 X 0.000001407212762 X (R2 = 0.89) cv- Kentwood NI: Y = 0.0405285386304 + 0.09106061667658 X 0.000001423001624 X (R = 0.89) I: Y = 0.028449637433 + 0.09107961761992 X 0.000001439563895 X (R = 0.88) .mm.m ousOHO 3 ...oo. mandmmouo QMEJaznuuc OON. OOO OOO OOO O H p . r . I b 5 L L I 5 n_. m: M. 0 3 .I Hy IL A 3 0 HO 0 M l H My 8 l 3 '0 J u_ a m m. OBS-...: ...--.- . Hm 8.8.2.2.... OI... H [0 ll 89:sz - 3 .... 9 D 2 1 15am. ecu mflmouo owncnscauum oom— oom ocw can 0 ..(h r b > L F O b P r m m w. .1 6 IL A 3 0 N. 0 H l H Mu U l 3 0 J a J... 0 a o w EGO-.... ...--... . B 8.3.2.2.... I H z-Sumzh 1 C :22: man mumomo mug-5:23: com. com com con 0 r I L T 5 P . I . 5 . n.v m. H. 0 3 HI . U ll- _ M 0 3 M 0 N. 0 H l 0 H 0 no 0 H. l 3 0 I . nu m w 88...... ..--.. n . 3 owhumuznzoz I a”... 0 ( 2.2.9.... -5 d. D .4208 w>mo mumomo mug-5:38.. oom— oom com com o. p p p p > L (P k > b L ) o m M .I U I. .1 A 3 0 M. 0 m. H H U 1 3 O / H“ 889.... ..--... a . H crow-3:20: I V,- zwzcmuum a 5 :28. 9.3 “Macao 3.52.3”... com. com com 00m 0. p > b (P ) w b > O > > 0 m w. 1 U IA A 3 0 n. 0 H w. M. 8 IL 3 0 \II a ...”... 0 O . .. o m 885:. ..--.. . 33... 8.3.2.2.... I W to 83...... - .6 9 .u 203 waq ummouo auhcnazauum com. com can com o. p > b 6 p h b 6 h b b o .... o 3.8.... ...--... . 8832.22. Ole ucn—zcm I B 9 130 relative growth rates in noninfected and B. penetrans infected plants (Figure 3.32). Relative growth rates of g. penetrans infected and noninfected Saginaw, Gratiot and Kentwood bean plants were similar (Figure 3.32D-F). The relationship between relative growth rate and degree days correlated well with a second degree polynomial type relationship as indicated by the equations and curves for the relation- ships between relative growth rate and accumulated degree days (Figure 3.32). For Sanilac noninfected plants the equation for the relationship is: Y = 0.0755662541602 + 0.0009430491099 X 2 — 0.000001340226071 x (R2 = 0.89) while the equation for Sanilac g. penetrans infected plants is: Y = 0.057526902686 + 0.00108419798777 X 2 (R2 = 0.92) - 0.000001352304453 X where Y = relative growth rate per week and X is accu- mulated degree days at base 10 C. The comparison of the equations shows the differences in growth rate of in- fected and noninfected plants. A comparison of equations expressing the relation- ship between relative growth rate and accumulated degree 131 days for noninfected and infected plants of Gratiot variety indicated that there was no significant difference in relative growth rates of noninfected and g. penetrans infected plants. For noninfected plants the equation for the relationship is: Y = 0.0800559470947 + 0.00101491572655 x 2 2 - 0.000001412741105 X (R = 0.85) and for E. penetrans infected plants the equation for the relationship is: y = 0.080009763156 + 0.0009800761301 x - 0.000001407212762 x2 (R2 = 0.89) 3.3.4.3 Responses of Sanilac navy beans to infection with different densities of Pratylenchus penetrans Final total population densities in roots and sOil associated with navy beans increased with increase in initial population densities of g. penetrans and the relationship between the log of initial and the log of final densities was correlated with a linear function (Figure 3.33) and expressed by the equation: Log Y = 0.34 + 0.93 (log X) (R = 0.96) where Y = log of final densities of g. penetrans plus one and X = log of initial densities of g. penetrans plus one. The percentage initial mortality was 20%, 20%, 50%, 11%, 24% and 38% for initial densities of 5, 10, 20, 80, 160 132 8— F— -2 O CD —<:: O —— m —o— —J5-— C) —45— A + __ do OS :5 ‘0 2: m ...,— 5 + -(5— O O 45- v—4 \ C0 _::: 2: 2: CE 3_ L00 Y : 0.34 + 0.93 [LOG X) m -J>— .— ir- R2: 0096 L; -5 LLJ .. 0. 0— ,_._T 1 LL111111 J 11111111 1 11111111 I llllllll T lllllll l 1111111!j 10 10 10 0 Pl/ 100 CM3801L Figure 3.33. Relationship between total (Root f soil) final population densities of E. penetrans and initial soil population densities of g. penetrans. 133 and 320 g. penetrans per 100 cm3 soil respectively. For an initial density of 40 g. penetrans per 100 cm3 soil the initial mortality was not obtained as population densities were higher than initial density at the time of sampling at 254 DD 10 C (Tables'A4-l,2.&}3). Population densities fluctuated over time. Two maxima in root population densities were evident and three maxima in soil population densities were observed (Figure 3.34) for populations associated with an initial 3 density of 320 g. penetrans per 100 cm soil. Root population densities increased steadily from initial growth until 523 DD 10 C and then decreased until 603 DD 10 C. Densities increased after this period reaching the second maxima at 865 DD 10 C (Figure 3.34). In thesmfljq densities decreased initially as nematodes entered the roots until 341 DD 10 C. The three maxima in population densities were observed at 434, 603 and 1094 DD 10 C (Figure 3.34). Lesions were present on roots of plants exposed to g. penetrans (Figures 3.35-3.36). These lesions are characteristic of the damage caused by root lesion nema- todes. The heights of plants exposed to initial densities of 20, 40, 80, 160 and 320 g. penetrans per 100 cm3 soil 134 .3- x P. PENETRRNS / 0 ROOT [D P. PENETRRNS / 100 CH3$0IL 1 H L‘ ‘ . '0 > _ - h .u ‘ r r f j r f r I r ' I I ' ' ‘1 Gb 300 600 900 1200 1500 RQCQHULBTEQ DEGREE QBY§ (flflggd Figure 3.34. Population dynamics of g. penetrans associated with navy beans exposed to an initial density of 320 g. penetrans per 100 cm3 soil. 135 Figure 3.35. Root-lesions produced by g. penetrans on navy bean roots. Pi = in§tia1 population density per 100 cm soil. Le = lesion 136 rl||1111141114 11 1‘ mm.m ousmflm 9.1. 137 Figure 3.36. Comparison of a noninfected and a g. penetrans infected navy bean root system. Le = lesion. .m musmflm. mm 139 were lower than the heights of noninfected plants (Figures 3.37-3.40). The relationship between plant height and log of initial population density was ade- quately expressed by linear functions with significant correlation coefficients (R) values for six time periods (341, 688, 782, 865, 967 and 1094 DD 10 C) (Figure 3.37). However for the time periods associated with 434, 523 and 603 DD 10 C the relationship between plant height and the log of initial population densities was corre— lated to second degree polynomial relationships (Figure 3.38). The curves for these relationships indicated increases in plant height at low initial population densities of P. penetrans. These increases in plant height were not evident at the other six time periods of growth. The relationship between plant height and accumu- lated degree days was curvilinear indicating increases in plant height with increase in degree days (Figures 3.39-3.40). Initial population densities above 20 P. penetrans 3 per 100 cm soil significantly (P = 0.05) reduced root area of plants (Figures 3.41-3.42) . The relationship between the log of initial population densities of P. penetrans and root area of navy beans was expressed 140 Figure 3.37, Relationships between navy bean plant height and initial soil population density of P. penetrans at different periods of growth. 1u41 .nm.m muomflm ooc— 4_ownzu 00— \_m oo_ o_ _ _ _ _ [o mm.o.. u x .x co... mm; u vo.oN N )- myco «a fi. .u Boo vmo: 0' lHOI3H lNUWd (H3) 4_own:u 00— \.m 4~omntu co" \_m _ co 4.0wnzu 00— \.m a. co_ a. , ¥1+IL$¥I|$§+TT110 mm.o - u a 1 .x oa3_ .m.n - up.m~ H y. .9 Eco Nor. m>¢o 3 V9 1H013H lNUWd (H3) ooo_ no. a_ 2 _ _ r 0 1| 8.0- u x I A. .x 8.: mm; - 2.8 n 5 8 N l H 3 0 H l m“ H .u 28 $2 «:6 2. V0 0 4.0wazu 00— \_¢ coo. on. o— _ 86 - u z I_d .x 8: m6 - 2.64. n » 10 m N l H 3 9 H I. ,1: m A E” ‘0‘ $23 cm .uo_oo coo. coo. on. o l _ _ _ n. 69.9 I u I I. Id 1'01 .x 8: 8.. - 3.8 u 5 W I. H 3 O H 1 mu u .u._aa moo. ”5:9 on v.0 o 310m.zu oo_ \_1 ooo_ oo_ o. _ rx++++IT||rx++++lfnlrx++++l+||+no T oa.o - u c o..a .I ..I 2 8.: E.~ - 2.4.. u 5 W I. H 3 9 H I. Mu nu .oo_oa _.n. m>co mu Ju42 .mpoHumm nu3oum ucmummmap um mcmuumcmm .m mo muflmcmp cofiumasmom awouflcw paw mannam :mwn w>mc mo unmflmn cmwzumn QHSmGOoumHmm .mm .m muswflm 4~ownzo oo~ \_L ooo. oo. o. _ rx++T+I+Ilrx+TT+|Tn|rx++++n+uu+.o T S .o.o ".5 v ..x ooh. .m._.._x oo3__~.o . .o.o~ u 5 ..m .lm ‘ 1 m“ a w. z (S .oo_oo moo. m5oo o. a e [0 lHOI3H lNUWd (H3) 4~owozu co" \_m ooo_ oo— o. _ rx++++I+Inrx++++|+nurx++++l+ul5.o T S T T mo.o ”.5 .15 ooo. o~._ - .5 oo3_ 55.o . oo.o_ u 5 1.0 ‘ ‘ I c 1.9 T w a . 1.m .oo_oo own. o5oo o. z lHOI3H lNUWd (H3) oooo.zo oo. \.¢ coo. oo— o. rx++++I+u:rx++++n+unr:++++n+uu4.o ..5 oooo 5o._ - .5 oo3_ 5o.~ . o..o. u 5 . .uo.oo vnv. 03.0 "a: ”pan an I 1H013H lNUWJ (H3) 143 Figure 3.39. Effect of P. penetrans on height of navy bean plants over the growth period. Equations for the relationships between plant height and accumulated degree days at base 10 C. Y = plant height ; X = accumulated degree days Pi = initial soil population density of g. penetrans per 100 cm soil. Pi = 0 ‘ Y = 34.21 — 7519 / X (R = - 0.99) Pi = 5 Y = 33.94 - 7369 / X (R = - 0.99) Pi = 10 Y = 33.32 - 7176 / x (R = — 0.99) Pi = 20 Y = 29.52 - 6064 / X (R = - 0.99) Pi = 40 Y = 27.34 - 5759 / x (R = - 0.99) 144 300 nccunu1nran DE GREE DRYS ( DD 111 n) Figure 3.39. 1 H Pl : 0 H P] : 0 O-QPI=S O ouoPlzlo E n g m L) L) 5— r— 5 S -1 ‘ H _ E 3 . ... a I I >— 1— 2 Z a: a E 2“ a 24 fi I 1 1 7 V 600 900 1200 300 500 900 1200 ncrunulnTED DEGREE DRYS (0010:] nrrtmulRTED DEGREE DRYS (00111:) 3‘ 9‘ ‘ H PI = H P1 = 9.4,, P. = 20 0‘ 9.9 P, = 40 g 8‘ z m L) L) E E (D O- 2 O— : ~ .1 .. I I r— : E E o E 2- E 2— ' I fl 1 1 fi 500 900 1200 ch 600 900 1200 300 RCCUHULQTED DEGREE oan (nomr1 145 Figure 3.40. Effect of g. penetrans on heights of navy bean plants over the growth period. Equations for the relationships between plant height and accumulated degree days at base 10 C. Y = plant height ; X = accumulated degree days. Pi = initial soil population density of P. penetrans per 100 cm soil. Pi = 0 Y = 34.21 - 7519 / X (R = —0.99) Pi = 80 Y = 24.84 - 5042 / X (R = -O.99) Pi = 160 Y = 22.87 - 4724 / x (R = - 0.98) Pi = 320 Y = 21.40 - 4374 / X (R = -0.98) 146 fio.ncu wrco mmmowc amba_:::cua oou— 0mm emu own DNM n f 0.10 On _L I f (H3) 1H013H lNHWd .oq.m wusmflm CON— 5 Huang. w5ca mucous nm5cozzzooa owo ooo own Dw_ u f 0.10 (H3) 1H013H lNUWd r. $1. —LI (H3) 1H013H lNUWd 147 Figure 3.41. Effect of different initial population densities of P. penetrans on root area of navy bean plants. 148 Ho.m 055655 €ng” -—-—/ Is 12 s e m. 5:31.00 8.x... 5 149 3’1 47 0915 (603 0010 ,1 CM?) ( CE LLJ 0: 0C ’— 03— Y =20.91—3.291L00x1 C3 0: _ R :‘0-99 to— I I l O 1 10 100 1000 Pl/ 100 CM3801L Figure 3.42. Relationship between root area of navy bean plants and the log of initial density of P. penetrans at 688 DD 10 C. 150 as a linear function indicating decreases in root area with increase in initial population densities of P. penetrans. This is supported by the high correlation coefficient R =-o,99 (Figure 3.42). The relationship between root area and accumulated degree days was first examined as a linear function from 254 to 688 DD 10 C and from 782 to 1094 DD 10 C (Figure 3.43). The low degree of correlation expressed by the R value, however indicated that a linear function did not adequately express the relationship. Second degree polynomial functions were developed to express the relationships between root area and accumulated degree days (Figures 3.43-3.45). Leaf area, shoot fresh weight, shoot dry weight and root weight were significantly (P = 0.05) decreased by initial population densities above 40 P. penetrans per 100 cm3 soil (Tables A5-A8). Dry bean yield was 'significantly reduced by initial population densities 3 above 40 P. penetrans per 100 cm soil (Figure 3.46). The relationship between initial densities of P. penetrans and dry bean yield was expressed by a linear function (Figure 3.47) and the equation for the relationship is: Y = 3.16 - 0.73 (log X) (R = -0.97) where Y = dry bean yield and X = initial density of 151 ) CM 0 1 ( ROOT RRER T I V Y ch 300 600 900 1200 RCCUMULRT D Y ( 0:) Figure 3.43. Comparison of linear regression functions and - a second degree polynomial function for the relationship between root area of navy bean plants and accumulated degree days. 152 Figure 3.44. Influence of different initial population densities of P. penetrans on root area of navy bean plants over the growth period. Equations for the relationships between root area and accumulated degree days at base 10 C. Y = root area ; X = accumulated degree days. Pi initial soil population density of P. penetrans per 100 cm3 soil Pi = 0 y = - 21.0092565907 + 0.1214843 406 x - . 0008441463627 x (R = 0.89) Pi = 5 y = — 19.8948515196 + 0.1115955 2098 x - 0.000075622876 x2 (R = 0.91) Pi = 10 y = -18.7327810622 + 0.108994753853 x - 0.00007494743561 x2 (R = 0.92) pi = 20 Y = - 16.667328816 + 0.0969584231 x - 0.00006708621327 x2 (R = 0.94) P1 = 40 y = - 13.1817518989 + 0.9316703 79272 x - 0.00005761614299 X (R = 0.92) 153 Dom * b F can P P ov .vv.m musmom ~95on. w»co unread duhmqatauuc com cow. com com P b h P b h 5 » 1 b ’ H386 1008 (133 ) o. 154 Figure 3.45. Influence of initial population densities of P. penetrans on root area of navy bean plants over the growth period Equations for the relationships between root area and accumulated degree days at base 10 C. Y = root area ; X = accumulated degree days Pi = initial soil population density of P. penetrans per 100 cm soil. Pi = 0 Y = - 21.0092565907 + 02121484324 6 X - 0.0008441463627 X (R = 0.89) Pi = 80 Y = - 9.65024395178 + 0.067730239 367 X - 0.00004783616595 X2 (R = 0.89) Pi = 160 Y = - 9.58037983025 + 0.365590300 395 X - 0.00004671772711 X (R = 0.87) P. = 320 Y = - 9.75174063684 + 9.0640076153808 X 0.000045979134 X (R = 0.89) 155 002 r b .mo.m muooflo ism—a. “Han uumuua QUHm EEGUQ 08 can b (1MB 1008 I. ‘- o. On at SJ 156 ‘r—1 ’— 2: c1: __ _J U) 0. \\ c5 _ C3 -J .— UJ OJ H >— d * 2: GE UJ no _ >— 0: C3 _ o 1' 1H1“? 1‘ iHHHi 4, 411.1111. 1 10 100 1000 P; / 100 CNasoIL Figure 3.46. Effect of different initial population densities of P. penetrans on yield of navy beans. Vertical bars represent 95 % confidence intervals. 157 DRY BERN YIELD (G/PLRNT) 51— Y : 3.16 - 0.73 R 2-0097 1 11111111 1 1 1111111 1 1 1111111 CD 1 1111111] I T 117111] 1 1111111] 1 10 100 1000 P,/ 100 0033011 Figure 3.47. Relationship between yield of navy beans and log of initial population density of P. penetrans 158 P. penetrans plus one. The signficant degree of corre- lation and confidence intervals (Figure 3.47) indicated that the relationship was appropriately described by this linear function. The growth response of plants varied depending on the initial population density of P. penetrans (Figure 3.48—3.49). Growth was not significantly reduced by low initial densities (Figure 3.48) but significant reduction in growth was observed at higher densities (Figure 3.48-3.49). The relative growth rate of plants was reduced by population densities above 20 P. penetrans per 100 cm3 soil (Figures 3.50-3.51). The relative growth rate of noninfected plants and plants exposed to an initial density of 5 P. penetrans per 100 cm3 soil followed similar trends over the growth period (Figure 3.50A). The relationship between relative growth rate and accumu- lated degree days was expressed as second degree poly- nomials (Figure 3.50-3.51). The equation for the relationship for noninfected plants is: Y = 0.105434974483 + 0.00142888178201 X 2 (R2 = 0.67) - 0.000001991528545 X while the equation for the relationship for plants exposed to an initial density of 5 P. penetrans per 100 cm3 soil is: 159 Figure 3.48. Effect of P. penetrans on growth of navy bean plants. o5.o munmflm 161 Figure 3.49. Comparison of growth of navy bean plants in the absence of P. penetrans and in the presence of an initial density of 320 P. penetrans per 100 cm soil. 162 11.1 . ....mov.m $1.545me :Om .80 2: \ .m Figure 3.50. Equations for the relationships between growth rate and accumulated degree days 163 Influence of different initial popula- tion densities of P. penetrans on relative growth rate of navy bean plants over the growth period. relative at base 10 C Y = relative growth rate per week ; X = accumulated degree days. Pi = initial soil population density of P. penetrans per 100 cm soil. Pi = 0 Y = 0.105434974483 + 0.00142888138201 X - 0.000001991528545 X (R = 0.67) Pi = 5 Y = 0.0942405452017 + 0.0915116983398 X - 0.000002072951014 x (R‘ = 0.69) Pi = 10 Y = 0.0291013809244 + 0.09186911 35134 X - 0.000002266413232 X (R = 0.67) Pi = 20 Y = 0.116545193601 + 0.00129545035131 X - 0.000001922417876 X (R = 0.58) P=4O Y= 0.0450555327553 + 0.03172991 54509 X - 0.000002540119343 X (R = 0.63) 164 T 600 H P] "'0 P1 -0050 0000 A 1 '1-00 A 0'1050 j T 600 900 Figure 3.50. 1 300 'fi 600 165 Figure3.51. Influence of different initial popula- tion densities of P. penetrans on rela- tive growth rate of navy beans over the growth period. Equations for the relationships between relative growth rate and accumulated degree days at base 10 C. Y = relative growth rate per week; X = accumulated degree days Pi = initial soil population density of P. penetrans per 100 cm soil. P- = 0 Y 0.105434974483 + 0.00142888138201 X (R - 0.000001991528545 X = 0.67) P- = 80 Y = 0.02864789416 + 0.001§041993 867 X - 0.000002090975285 X (R = 0.50) Po = 160 Y = 0. 0.0362586010281 + 9.0012936133828 X - 0.000001903869134 X (R = 0.59) P- = 320 Y = 0.0128353084284 + 0.09161252 92496 X - 0.000002408870322 X (R = 0.73) 166 .L 0110 —m I Iffif 00'!- * W ' jfi 09'1J° 00'0 09'0- OS'O cou— Hm.m musmfim v 1 00'!- V T ‘r ‘7 00'0 OS'O‘ *7 r q 1 00'! OS°O V I 05'! 09:15” CON— 5 o..oo. o5¢o humouo ou5ooo=ouoo ooo ooo oon o. h b b r h b I b h r 0.. m. o .0 ... . co 00 .nu . in M: v o 0 v. o 0 o m. 0 1 _ .- .... m_ oo .. l o. 0 who 0 o ...o 411. . 167 Y = 0.0942405452017 + 0.00151169383398 X 2 (R2 = 0.69) - 0.000002072951014 X This indicated the similarity in growth response between noninfected plants and plants exposed to an initial density of 5 P. penetrans per 100 cm3 soil. A comparison of relative growth rates of noninfected plants and plants exposed to an initial density of 10 3 P. penetrans per 100 cm soil indicated that initially the relative growth rate of infected plants was lower than that of noninfected plants (Figure 3.50B). After 260 DD 10 C, however, the growth rate of infected plants increased above that of noninfected plants (Figure 3.508). The differences in relative growth rates for these two treat- ments (0 and 10 P. penetrans per 100 cm3 soil) are also evident from the equations for the relationships. For plants exposed to an initial density of 10 P. penetrans per 100 cm3 soil the equation is: Y = 0.0291013809244 + 0.00186911335134 X 2 2 - 0.000002266413232 X (R = 0.67) and the equation for noninfected plants is: Y = 0.105434974483 + 0.00142888178201 X 2 (R2 = 0.67) - 0.000001991528545 x Comparison of the first terms of these two equations indicates the initial lower growth rate in infected plants, 168 while comparison of the second terms of the equations indicates the increase in relative growth rate in infected plants after 260 DD 10 C. The relative growth rate of plants exposed to initial densities of 20 and 40 P. penetrans per 100 cm3 soil respectively followed similar relative growth rate trends as that of noninfected plants from initial growth until 175 DD 10 C and 325 DD 10.C respectively. After these periods the relative growth rate of infected plants were lower than that of noninfected plants (Figures 3.50C, D). The relative growth rate of plants exposed to an initial density of 80 P. penetrans per 100 cm3 soil was slightly lower than that of noninfected plants (Figure 3.51E). Growth rates were similar at 300 DD 10 C following which the growth rate of infected plants remained lower than that of noninfected plants (Figure 3.51E). The relative growth rate of plants exposed to an initial density of 160 and 320 P. penetrans per 100 cm3 soil respectively were lower than that of noninfected plants throughout the growth period (Figure 3.51F, G). For plants exposed to an initial density of 320 P. penetrans per 100 cm3 soil the equation for the relationship between relative growth rate and accumulated degree days is: 169 Y = 0.0128353084284 + 0.00161252592496 X 2 - 0.000002408870322 x (R2 = 0.73) and the equation for the relationship in noninfected plants is: Y = 0.105434974483 + 0.0014288178201 X 2 2 = 0.67) - 0.000001991528545 X (R Comparison of these two equations indicates the decrease in growth rate in plants exposed to an initial density of 320 P. penetrans per 100 cm3 soil. Growth rates were lowest in plants exposed to the highest initial density of 320 P. penetrans per 100 cm3 soil (Figure 3.51G). 3.3.5 Discussion Studies on the pathogenicity of Pratylenchus penetrans on navy beans indicated that this plant parasitic nematode species can penetrate navy bean roots, feed and reproduce. The plant response to infection by this nema- tode varied depending on the bean variety and the initial population density of P. penetrans. The results of the study on pathogenicity (3.3.4.1) indicated that densities of P. penetrans above 25 per 100 cm3 soil can affect the physiological functioning of plants resulting in detri- mental growth and significant reduction in dry bean yield of Sanilac bean variety. In this study the lowest initial population 170 density included in experimental procedures was 25 P. penetrans per 100 cm3 soil. Examination of the regression of the log of initial density of P. penetrans on the log of final densities of P. penetrans indicated the necessity for studies involving lower initial densities of P. penetrans. The importance of initial population density in relation to final density and yield of plants has been stressed (Wallace, 1973; Oostenbrink, 1966; Seinhorst, 1966; Norton, 1978). The need to examine effects over the growth period was also evident. Evans, (1972) pointed out that in considering relationShips between plants and their environments the complete cycle should be examined. Studies over time could assist in elucidating critical periods when some state of the environment, the pest and plant species interact to determine the functioning of the ecosystem. Sanilac, Seafarer and Tuscola navy bean varieties were highly susceptible to infection by P. penetrans, while Gratiot, Kentwood and Saginaw varieties were more tolerant to infection by this nematode species. P. penetrans penetrated roots of all varieties and reproduced. The response to infection, however, differed among varieties, in that growth parameters such as plant height, root weight, and relative growth rate were not significantly decreased 171 in Gratiot, Saginaw and Kentwood varieties, while detrimen- tal effects on these growth parameters were observed for Sanilac, Seafarer and Tuscola varieties. The yield of dry beans from Sanilac, Seafarer and Tuscola varieties respectively were reduced by infection with P. penetrans while there was no significant decrease in yield from P. penetrans infected Saginaw, Gratiot and Kentwood varieties. All varieties were exposed to similar 3 initial densities of 150 P. penetrans per 100 cm soil. The lower population densities maintained on Saginaw, Gratiot and Kentwood varieties and the observation that these densities had no significant detrimental effect on growth and yield of these varieties indicate that these three varieties are to some extent tolerant to P. penetrans. The plants' response to infection was such that the reproductive potential of P. penetrans was reduced on Saginaw, Gratiot and Kentwood varieties compared to the reproductive potential on Sanilac, Seafarer and Tuscola varieties respectively. If the number of generations of P. penetrans is related to the number of maxima in population densities, three generations were evident on Sanilac, Seafarer and Tuscola varieties respectively and, two generations on 172 Saginaw varieties and one generation on Kentwood variety (Figure 3.28). However because of the overlapping nature of life cycles of P. penetrans the number of generations associated with a particular crop is not always deter- mined by the number of maxima in population densities of P. penetrans. The discovery of bean varieties tolerant to P. penetrans is critical for development of optimum integrated management strategies in bean production. The choice of variety however is dependent on other factors such as effects of other pests, yields and eco- nomics of production. For example while Gratiot bean variety is tolerant to P. penetrans it has not gained economic importance in Michigan, and this is related to the yields and time to maturity of bean seeds (Adams, 1978). In time study on responses of Sanilac navy beans to infection with different initial population densities of P. penetrans at different intervals during the growth period (3.3.2.1) the initial densities ranged from 5 to 320 P. penetrans per 100 cm3 soil. The low range was chosen to observe effects which were not studied in the experiment on pathogenicity (3.3.1.1). Sanilac navy bean variety was chosen as it appeared to be highly suscep- tible to P. penetrans. The significance of initial 173 nematode density as a determining factor on yield and population dynamics of nematodes has been noted. Olthof and Potter (1973) observed a positive correlation between yield and initial density. Robbins eg 31. (1978) reported on an inverse relationship between yield and Pratylenchus spp. A salient feature of the research findings is that low densities of P. penetrans can cause increases in plant growth. This was also evident from the study on pathogenicity (3.3.1.1) where root weight and root length of navy beans were increased by population densities of 25 P. penetrans per 100 cm3 soil (Figure 3.25). Increased growth responses to infection by low densities of nematodes have been observed (Wallace, 1973), and is related to a resistance response of the plant to infection by P. penetrans. The threshold density for damage was 40 P. penetrans per 100 cm3 soil. The threshold density is however depen- dent on temperature, soil moisture and the associated host crOp (Wallace, 1973; Norton, 1978). While all replicates of treatments did not respond to the same degree, typical responses are evident in Figures 3.36, 3.41, 3.48 & 3.49 Some degree of stunting was observed but this is not. always evident in the field. The periods of sampling were converted to degree 174 days as this concept of degree days allows for correlation between a physiological determination factor of temperature with physiological development of plants and organisms. The relative growth rate of plants was studied by sampling at close intervals during the growth period. Because of the small size of plants, changes over one day periods would not be measurable hence the choice of weekly sampling intervals. Examination of relative growth rates allows broad generalized observations on the growth pattern of plant species over time. Relative growth rate is a physiological growth index and examination of the relationship between this growth index and a physiological time parameter of degree days is appropriate as the growth of plants is influenced to a large extent by temperature. There are however practical difficulties associated with the use of the physiological index of relative growth rate (Evans, 1972). In practice it is not possible to use the same plant to determine initial dry weight and final dry weight for any two growth or sampling periods. This requires use of two different plants which may not be identical in growth form and genetic makeup. The use of large numbers of replicates and uniform genetic planting material can, however reduce the error associated with application of relative growth rates. 175 The results from studies on relative growth rate indicated that generally at low population densities of P. penetrans, relative growth rates were initially lower than in noninfected plants, but with time the P. penetrans infected plants were able to overcome the detrimental effects associated with infection by P. penetrans and relative growth rates were similar in P. penetrans infected and noninfected bean plants during the latter phases of plant growth. Exceptions to this were observed. In one case infection by low densities of 10 P. penetrans per 3 100 cm soil increased the relative growth rate of bean plants (Figure 3.508). This could be related to a resis- tance response of the plant to infection. At high densities relative growth rate was generally lower in infected plants throughout the growth period. Relative growth rate responses vary depending on the plant species. Slinger (1976) observed initial decreases followed by increases and then further decreases in relative growth rate of carrots (Daucus carota L) over the growth period. The initial decrease however can be correlated with changes in source-sink relationships associated with formation of the tap root. For navy beans relative growth rate initially increased reaching a peak during the growth period and then decreased at the onset of senescence. 176 3.4 Influence of Environmental Parameters of Temperature and Moisture 3.4.1 Influence of Temperature Growth, development and activity of organisms are influenced by temperature. For most organisms there is a threshold temperature below which reproduction and development cannot take place, and above which detrimental effects on growth results. Temperature can be considered as a source of heat units or energy available to facilitate biological processes. The following studies were designed to examine the effect of temperature on P. penetrans associated with navy beans. 3.4.1.1 Effect of different temperatures and different initial densities of Pratylenchus penetrans on growth and yield of navy beans and on final population densities of Pratylenchus penetrans 3.4.1.1.1 Method The experiment consisted of a 2 x 2 factorial design of three replicates of four treatments of P. penetrans at four temperatures. P. penetrans treatments included densities of 0, 25, 150 and 300 per 100 cm3 soil. Temper- atures studied included 15, 20, 25 and 30. Forty-eight 2.36 cm clay pots were filled with 1000 cm3 sterilized 177 sandy clay loam soil. Four temperature control chambers were arranged to hold 12 of these clay pots respectively. The temperature control chambers were maintained at 15, 20, 25 and 30 C respectively. P. penetrans were extracted from roots of Sanilac navy bean plants propagated in culture boxes in the greenhouse. A suspension containing a calculated density of P. penetrans was prepared. The appropriate densities for this study were added to the soil in pots by extracting calculated aliquants of the suspension and transferring these to the soil in pots. Three navy bean seeds were planted in the soil in each pot. Two days after germination, plants were thinned out leaving one seedling in the soil in each pot. Plants were watered daily as required and maintained in the temperature chambers in the greenhouse for a period of 96 days. Plant height, shoot dry weight, root weight and dry bean yield were recorded after this period. Soil and root samples were taken for nematode analyses (3.1.1.2 and 3.1.2.2) and P. penetrans densities were determined (3.1.3-3.1.4). 178 3.4.1.2 Interactions of temperature and P. penetrans associated with navy beans over the growth period 3.4.1.2.1 Method A 2 x 2 factorial design of three replicates of two densities of P. penetrans (0 and 150 per 100 cm3 soil) and four temperatures (15, 20, 25 and 30 C) was used in this study. Twenty-four 2.36 cm clay pots containing 1000 cm3 sandy clay loam soil were arranged in each of the four temperature chambers maintained at 15, 20, 25 and 30 C respectively. P. penetrans were extracted from roots of navy bean plants which were propagated in culture boxes in the greenhouse. A suspension containing a calculated density of P. penetrans was prepared. Calculated aliquants of this suspension were added to soil in 12 of these pots to obtain an initial population density of 150 P. penetrans per 100 cm3 soil. The soil in the other 12 pots served as controls. Three navy bean seeds cv Sanilac were planted in the soil in each pot. Plants were thinned out three days after germination leaving one seedling in the soil in each pot. Plants were watered daily and maintained at the 15, 20, 25 and 30 C respectively in the greenhouse for a period of 91 days. Shoot fresh weight, leaf area, plant height, root 179 area, root weight and root length were recorded at four intervals during the growth period. Shoot systems were oven dried at 30 i 5 C and shoot dry weight was recorded. Dry bean yield was recorded after the 91 day growth period. Soil and root samples were taken at 4 intervals for nematode analysis (3.1.1.2 and 3.1.2.2) and P. penetrans densities were determined (3.1.3—3.1.4). 3.4.1.3 Results 3.4.1.3.1 Effect of different temperatures and different initial densities of P. penetrans on growth and yield of navy beans and on final population densities of P. penetrans Final soil population densities of P. penetrans were lower than root densities (Figure 3.52;Tables.A9vAll). Population densities increased with increase in temperature reaching maximum densities at 25 C and then decreasing above this temperature (Figures 3.52-3.53). The highest densities were associated with soil infested with the highest initial density of 300 P. penetrans per 100 cm3 soil. Interactions of temperature and P. penetrans had a significant effect on final population densities (Figure 3.53). For all sampling periods and at all temperatures the highest percent of the population cohort consisted of females (Table 3.12). The percentage of 180 5566 5566 3566 m m m mcmuumcum .M mo mmfluflmswc :ofiumasmom co wusumummemu mo oocmoamcH no. On 5 lo: $333155 mm 8 m. 2 p F L .o 0 1d 1” Cal U l 0 N 0 3 1N S 01 1 1A 585. o \ 2&5:qu ... c 1 0 ion 5 oo_ \ 9.5:qu .e ... o EU ooa umm mcmuuwcwm .m com mo xuomcwp HmHuHCH EU ooa Hod mcmuumcwm .mloma mo wuflmcmp amouflcfl EU OCH Mom mcmuuwcmm .m mm mo >uomcmp Hmwuflcfi n ADV Amv A>mc cuflz meMAUOmmm .m. .o: On » $353125 mo mo 2 p h /\ boom 0 \ mzamhuzum .m G 4_ow :u 00— \ wzcxhwzum .m I I I AlISN30 NOIlUTHdOd 0 0 01 .Nm.m 055655 .o: /\ /\ 2: ion to o2 \ 9&5:qu ... n 0 mmseqmumEMH mo om 2 S b p r 01 I AlISN30 N01183030d 0 5001 o \ wzathzum .m G 01 181 C) S— 33: ‘ } ..... {PI : 150 c: $3 C8314 }——--<| PI : 300 /k ._J C) 03 C) m fourth stage juveniles > males > third stage > second stage at 15 C. At 20 C the order of magnitude was females > fourth stage juveniles > second stage juveniles > males > third stage juveniles. At 25 C the order was females > fourth stage juveniles > males > third stage juveniles > second stage juveniles, and at 30 C the order was females > fourth stage juveniles > males > second stage juveniles 9 third stage juveniles (Table 3.12). Plant height, root weight, shoot dry weight and dry bean yield were significantly (P = 0.05) influenced by interactions of temperature and P. penetrans (Tables A12-A14). Plant heights increased with increase in temper- ature (Figure 3.54). There was no significant (P = 0.05) difference in plant height of noninfected plants and plants exposed to an initial density of 25 g. penetrans per 100 cm3 soil at temperatures of 15 and 25 C respectively (Figure 3.54A). Plant height was significantly (P = 0.05) reduced by population densities of 150 and 300 g. penetrans 3 per 100 cm soil at temperatures of 15, 20 and 30 C respectively (Table A12). Shoot dry weight was significantly (P = 0.05) reduced by all densities of P. penetrans at the four 184 .mcmnuwcwm .M mo mwfluflmcwp Hmfluflcfl acoumwwflp Ou ommomxw mucmHm coon >>mc mo Amy acofiws who pooch pcm A_ 0: D '1 C) ' I " I 1 l ' l T 1 10 15 20 25 30 35 TEMPERRTURE (“c1 Figure 3.56. Effect of temperature on yield of navy bean plants exposed to different initial densities of P. penetrans 188 3.4.1.3.2 Interactions of temperature and g. penetrans associated with navy beans over the growth period Total population densities of P. penetrans steadily increased from day 12 to day 91 of the growth period at temperatures of 15, 20 and 25 C respectively (Figure 3.57; Table A16). At 30 C total population densities increased reaching maxima at day 35 of the growth period. Soil population densities of P. penetrans decreased initially as nematodes entered roots and later increased as nematodes migrated from decaying roots into the soil at the end of the growth period (Tables A17-A18). Shoot dry weight was significantly reduced by g. penetrans at harvest at all temperatures (Figure 3.58; Table A19). Dry weight increased over the growth period reaching maxima at 57 days of growth and then decreased (Figure 3.59) after this period. Root area of noninfected and infected plants increased over the growth period reaching maxima at 57 days of growth (Figure 3.60; Table A20). 3. penetrans decreased root area at temperatures of 15, 20 and 25 C respectively (Figure 3.60; Table A20). Root weight, plant height, shoot fresh weight, root length and leaf area were significantly (P = 0.05) 189 300 400 . 1 1 1 200 1 P-PENETRHNS+IOO CM5801L+G ROOT V 0 20 45 55 80 100 TIME (DRYSJ Figure 3.57. Influence of temperature on population dynamics of P. penetrans over the growth period of navy beans. 190 D. D «l 15 c o)“ 20 c F A 1 H noun: Ecrco .- ‘ H NONINFECTED E sun-o xurccrto E o-mo mscrso (I m c: 1n _1 ..1 ..1 ._, KL "- n- .— \ \ D J O y— I'— I: I O 0:4 o 0" r... ... b-d urn Lu h.) 3 3 >— 1 >- ‘ . [z m "o' § C) U? D u) o .......... g” ‘ F- OT '- D.‘ “ O O ‘. O . I 1 g ‘ D K0 (0 O D ' f T f r * ' I 7 1 . ' V ' ' ch 20 4o so so 100 ch 25 41') 60 80 30 THE (BOYS) TIflE (DHYS) O J 25 c “r 30 c F _. 1 H NONI" ECTEO 1‘ ‘ H uouxurccrco mrurco )- E. 9' '0 E gnu-o INFECTED )(I U) AJ 4 J C‘ (L m n- "' \ \ o o H 4 P ‘ 3; E O 4 o 9., L—I N P- .- Lu Lu 3 :z 1 4 P * a: n: c. D u: 4 '4 p— .— F- o o 8 . O \ I + I 4 D U) 0') ‘3 v Y v w v 1 ' t ' 1 f I V I v I * Y ' 1 Ch 20 40 so so 100 ch 20 40 so so 100 THE (OMS) IIHE IDRYS) Figure 3.58. of navy beans over the growth period at four temperatures. Effect of P. penetrans on shoot dry weight 191 mcmuumcmm .M can omuowwcficoc mo unmwm3 >up uoocm co mnsumummEmu mo uommmm .poflumm Luzoum may um>o mucmHm coon >>mc Umuommcfl waaag mzHH 8 8 o P t 1 1 ms 1 ma .0 0 1 0 T. S 1m 1 .9 8552135561.; .3 00 1HOI3M AHO lOOHS (lNUWd/O) .mm.m musmflm L Hw>aov mzHc mm 0v ON c h _ L omkuwmzmzoz lHOIEM A80 lOOHS (lNUWd/O) l9 2 15 C H NONINFECYED o-u-Q INFECTED [9 CH ) l0 15 RR OUT (I I I 1 1 ‘0 60 BO 100 TIME (DRYSJ 00] CH'] I ROOT HRER 20 C H NONINFECTED ....Q xnrzcrco 20 ‘0 60 BO TIflE [DRYS) 25 c H nuuxmcrsn 9.1-3, lurscrzo 30 c H NONINFECTED .....Q W'ECYEO A 2‘ E U a 2- [LI _.- K " a y— x O 1’ 6‘ g m- d - 20 40 so so 100 ch 21': 41') 60 35 1110 TIME (DHYEJAAA, TIME (DRYS) FIgure 3.60. Effect of P. penetrans on root area of navy bean plant; over the growth period at four temperatures. 193 reduced by P. penetrans at 57 days of growth (Tables A21-A25). Dry bean yield was significantly (P = 0.05) reduced by P. penetrans at all temperatures (Figure 3.61). Dry bean yield of noninfected plants increased with increase in temperature reaching maxima at 25 C. Dry bean yield was significantly (P = 0.05) lower at 30 C compared to yields at 20 and 25 C (Figure 3.61). 3.4.1.4 Discussion The importance of the influence of temperature on growth, reproduction and infection of nematodes has been noted and several reports on effects of temperature on growth and development of nematodes and effects on plant growth and yield have been documented (Chapman, 1957; Patterson gt_§l. 1967; Mamiya, 1971; Radewald g£_§l. 1971; Wallace, 1973; Dunn, 1973; Miller and Rich, 1974; Acosta and Malek, 1979; Malek, 1980). The results of studies on effects of temperature on P. penetrans and effect on growth of navy beans indicated that temperature significantly influenced g. penetrans effect on navy beans. Lower population densities associated with navy beans at 15 C indicated lower development and reproduction at this temperature. This suggests that 15 C is below the threshold temperature for development and 194 2.5 1 O l—I (G/PLHNT] 2 'a—( l o_1 l 0-( DRY BERN YIELD O ———— NONINFECTEO INFECTED 0.0 10 1 I j 15 20 25 30 35 TEMPERRTORE 1°51 Figure 3.61. Influence of temperature on yield of noninfected and P. penetrans infected navy beans. Vertical bars represent 95 % confidence intervals. 195 reproduction of P. penetrans associated with navy beans. Higher population densities were observed at 20 and 25 C compared to densities at other temperatures. The highest population densities were observed at 25 C and this indicates that this temperature is optimum for development and reproduction of P. penetrans on navy beans. Acosta and Malek (1979) observed similar responses of maximum densities of Pratylenchus penetrans and P. vulnus asso- ciated with soybeans. Decreases in population densities of B. penetrans at 30 C were observed and similar responses were observed by Mamiya (1971), who observed reduced oviposition at temperatures of 30 C compared to oviposition at 20-24C. Population densities of g. penetrans increased with time at all temperatures. The fluctuations in densities observed in previous studies were not evident, and this is related to the choice of sampling date. Limitations in space in temperature control chambers dictated the number of pots which could be utilized in this study and conse- quently influenced the number of sampling periods. The four sampling intervals chosen appeared to correspond to maxima in pOpulation densities. In order to obtain detailed responses on population dynamics of P. penetrans associated with navy beans it is necessary to sample as often as 196 possible with a minimum of six sampling periods. The higher densities associated with navy beans at a temperature of 25 C is related in part to the greater availability of food from larger root systems formed at this optimum growth temperature. Poor plant growth and smaller root systems with less food source could be responsible in part for the lower densities observed at 15 and 30 C respectively. The nature of the population cohort was also influenced by temperature. The prOportion of second stage juveniles increased over the growth period indicating reproduction was taking place. Final population densities consisted generally of higher percentages of females and fourth stage juveniles compared to other stages. This could be related to the ability ofthese stages to with- stand adverse effects of toxins from decaying roots to a greater extent than other younger stages and males. The detrimental effect of high and low temperatures on physiological processes in plants contributed to de- creases in bean yields. Metabolic processes which promote assimilation of carbohydrates for plant growth and transport of these products are temperature dependent (Leopold, 1964), and at low temperatures the enzyme and hormonal systems which initiate and maintain these processes may not function efficiently. 197 The influence of temperature on P. penetrans and effects on navy beans is important for the development of nematode control strategies in navy bean production. The recommended planting date for navy beans in Michigan is late May to early June. At this time in Michigan temperatures range from 15 to 18 C. At these temperatures population densities are maintained at low densities due to the lower reproductive potential and high mortality. The percentage of crop loss is dependent on the initial density of P. penetrans, therefore crop losses can be minimized in the presence of low initial densities of P. penetrans. The choice of an early planting date when densities are low can be considered as an effective control strategy. The choice of planting date is, however, influ- enced by other factors besides optimum temperature for low densities of P. penetrans as Optimum temperatures for germination significantly influences yield. 198 3.4.2 Influence of Soil Moisture Soil moisture is an important environmental parameter which influences the growth and development of plants, nematodes and other organisms. Soil moisture is highly dependent on soil type. Nematode activity occurs mainly in the thin film of water surrounding soil particles and through pore spaces, therefore, soil mois- ture and pore space which are influenced by soil type are critical for survival of nematodes. This study was designed to examine the interactions of soil type, soil moisture and P. penetrans associated with navy beans. 3.4.2.1 Development of soil moisture characteristic curves for three soil types 3.4.2.1.1 Method In this experiment the volumetric percentage of moisture associated with four matrix potentials was determined in order to develop soil moisture characteristic curves for a sandy clay loam, a sandy loam and a clay loam respectively. Two replicates of 10 cm soil cores were prepared for each soil type. The soil cores were placed in a tray containing water and allowed to become saturated. The saturated soils were then subjected to pressures of 4, 30, 100 and 1500 centibars. The soils were weighed 199 prior to saturation with water. After moisture was re- moved from the soils at the respective pressures soils 'were reweighed. Soil cores were then oven dried at 105 C and reweighed. The percentage moisture associated with each pressure was calculated for each soil type (3.1.9). Soil moisture characteristic curves for each soil type were developed by plotting percent soil moisture versus matrix potential in negative centibars where soil matrix potential corresponded to pressures of 4, 30, 100 and 1500 centibars. 3.4.2.2 Interactions of soil type, soil moisture and P. penetrans asso- ciated with navy beans 3.4.2.2.1 Method The experiment consisted of a three factorial design of three replicates of two levels of g. penetrans (0 and 150 per 100 cm3 soil) at six moisture levels corresponding to soil matrix potentials of 5, 10, 50, 100, 500 and 1000 negative centibars, in three soil types including a sandy clay loam, a sandy loam and a clay loam (Table 3.13). Fifty-four 1 liter wax lined polythene cups were filled with 1000 cm3 of each soil type. Soils were adjusted to the desired matrix potentials (Table 3.13C) by weighing soils in cups and adding calculated 200 Table 3.13A Volumetric soil moisture content as related to matrix potential Sgtggtial Vglumetrig pgrcent moisgurg (-centibars) 1 ay an Y C ay an y oam loam loam O 58.99 53.33 36.06 4 50.83 35.66 30.35 30 48.48 30.72 24.18 100 45.11 20.53 19.34 1500 40.10 26.82 13.53 Table 3.13B Mechanical composition of soils Clay Sandy clay Sandy loam loam loam % clay 36.52 22.52 18.88 % silt 32.36 11.08 13.44 % sand 31.12 66.40 67.68 Table 3.13C Percent soil moisture asso- ciated with different matrix potentials Matrix Volumetric percent moisture potential _ . Clay Sandy clay Sandy ( centibars) loam loam loam 5 48 33 25 10 47 31 25 50 44 27 21 100 45 28 19 500 39 26 15 1000 38 25 14 201 quantities of water required to adjust soil water content to the desired matrix potentials. The soil in these cups was sterilized initially and served as noninfested g. penetrans soil. Fifty-four similar polythene cups were filled with sterilized soil from each soil type to give 18 cups of each soil type (three replicates for each treatment). A suspension containing a calculated density of P. penetrans was prepared by extracting P. penetrans from navy bean roots propagated in culture boxes in the greenhouse. Calculated aliquants of this suspension of nematodes were pipeted in to the soil in these cups to give initial 3 densities of 150 P. penetrans per 100 cm soil. Soils were adjusted to the desired moisture potentials by weighing and adding calculated quantities of water (Table 3.13C). Two navy bean seeds cv Sanilac were planted in the soil in each cup. Plants were thinned out leaving one seedling in the soil in each cup. Soils were main- tained at the desired moisture potentials by weighing to an accuracy of 1.0 g, and adding appropriate quantities of water. Plant height, shoot dry weight, root area, root length and weight were recorded after 92 days of growth. Dry bean yield was determined at the end of the period. Soil and root samples were taken for nematode 202 analyses (3.1.1.2 and 3.1.2.2) and P. penetrans densities were determined (3.1.3-3.1.4). 3.4.2.3 Effect of interactions of soil type, soil moisture and initial population densities of P. penetrans on growth and yield of navy beans and on population densities of P. penetrans 3.4.2.3.1 Method The experiment consisted of a 3x3x4 factorial design of three replicates of three soil types at three moisture levels with four initial population densities of P. penetrans. The soil types included a sandy clay loam, a clay loam and a sandy loam. The soil moisture levels corresponded to matrix potentials of S, 50 and 1000 negative centibars respectively. Initial densities of P. penetrans included 0, 25, 150 and 300 P. penetrans per 100 cm3 soil. Three hundred and twenty-four wax-lined polythene cups were filled with 1000 cm3 of the appropriate soil type to obtain the desired number of replicates. A sus- pension of P. penetrans was prepared by extracting nema- todes from navy bean roots propagated in culture boxes in the greenhouse. The desired densities (25, 150 and 300 3 g. penetrans per 100 cm soil) were added to the soil by 203 transferring aliquants of this suspension to the soil in appropriate cups. One hundred and eight wax lined poly- thene cups were filled with steam sterilized appropriate soil types to obtain the desired number of replicates. These soils served as controls containing a density of 3 0 g. penetrans per 100 cm soil. Soils were adjusted to the desired moisture levels and maintained at these levels by weighing and adding water as required (Table 3.13). Two bean seeds were planted in the soil in each cup. Plants were thinned out leaving one seedling in the soil in each cup. Plant height, leaf area, shoot dry weight and root weight were recorded at four intervals during the growth period of 94 days. Dry bean yield was determined after this period. Soil and root samples were taken for nematode analyses (3.1.1.2 and 3.1.2.2) and P. penetrans densities were determined (3.1.3-3.1.4). 3.4.2.4 Results 3.4.2.4.1 Development of soil moisture characteristic curves for three soil types The soil moisture characteristic curves developed for the three soil types indicated that the percent soil moisture increased in the order of sandy loam > sandy clay loam > clay loam. High moisture content was 204 associated with the clay loam even at a matrix potential of -1000 centibars (Figure 3.62). 3.4.2.4.2 Interactions of soil type, soil moisture and E. penetrans asso- ciated with navy beans Final root pOpulation densities of g. penetrans were significantly influenced by interactions of soil type and soil moisture (Figure 3.63; Tables A26-1—A26-5). Population densities were lowest in the clay loam and highest in the sandy loam (Figure 3.63). Densities of P. penetrans were lowest at a matrix potential of -lOOO centibars (Figure 3.63A, C). Population densities were highest at a matrix potential of ~50 centibars in all soil types (Figure 3.63A, C). Soil population densities of P. penetrans were also low at a matrix potential of -1000 centibars increasing with increase in soil moisture at a matrix potential of -50 centibars and then decreasing at high soil moisture levels corresponding to -5 centibars (Figure 3.64B, C). Final densities of P. penetrans in soil were influenced by interactions of soil type and soil moisture (Figure 3.64; Tables A27-1-A27-5). Population densities were significantly (P = 0.05) lower in the clay loam compared to densities in the other soil types (Figure 3.64A, B; 205 C)-—- mg [:1 SRNDY LURM 01" A SHNDY CLHY LORM CE OD x CLHY LORM F—CD ZO— LLJO OH | —Jcn CEO__1 }__ Z L1_J F— C) 0—0 XC—i O: 1.- CI: Z H V T T I 1 fir I U 7 ‘ T I j O 20 40 SO 80 SOIL MOISTURE [VOLUMETRIC%J Figure 3.62. Volumetric soil moisture content associated with three soil types at different matrix potentials. 206 1: a IHmCmp cowumasaoa uoou Hmcwm co on mfimuumcmm iii . mfimhumcwfi .m mo 5555 .m we suamcme Hagugcw oam musumwofi Hwom paw Amv mcmuumnmm .m mo muwmcmp Hmfiuwcfi cam mm%u HHOm .A228 5:158; 33 u ,‘R 183 (110$ {D (I)! / mm '0 All“ OHM WIUII .3: >5... fi1z.-;fi -tij,,1 34 Rd S g.— g SR! c \ shit .3 >2: 5:: z: m 5.21-1.1! II' -ll. (1108 (I) N! / mm 'd) um: 011M Willll .m®.m 115515 3.. »«d 53 58 g 53 Ba fiIIIITMMII .m!!!llfif::||. 1Hu 1i!¢$l.1IL . TitzéithT . T O WU 1+ 1 . {I ITWTILWU: 1-12-11 5 1 T7: -nw. III—HT .lll § I!:-n.7: -11.. TIA. -tIJ 51 i4 1: 1 13...! CR! o \ gpflt .3 5528 82538; i: c I THINK” llllfi‘ (Willi? ' 207 .mcmuumCmm .m mo mmwuwmcop cowumaaaoa Hwom Hmcfim co .on mcmuuwcum .m mo mufimcmlemauHcH paw eunumfioa HHOm oam .Amv munumwofi Hwom paw mama HHOm .A238 8:; .3: u 3.8 n6 Bu \ g .6 p23 5:? i: m < HNfiUHCH UCN 0Q%U HHOm MO wCOHUUMHUUCH MO MUCUDHMCH .¢©.m QHDth as 82 1 is =3 is 3... BS 53 53 53 So is So 53 is 53 1 m m «LT mu 111T a m u m. an TlffiWITmU WU. am m . Ill mu, 1m. 1w .. m m 71 ...Pl 114 n1 1“. FT. FT . L1] 8. m I A. ,l .111 n. 1 ...... I4 0 M. II;..11 TmTuITII mu! (Ililpm.wlll-.ll1 an m m 0 II The l I .5 ga 3.8 n5 8— ‘ g .8 >23 8:: .3: am— (‘IIOS ‘0 an I swam 'd) All” ”HM TIHIII 208 Table A27-l). Total population densities in soil and roots associated with navy beans were lowest in the clay loam soil, and highest in the sandy loam (Figure 3.65). For all soils P. penetrans densities were lowest at the high- est moisture level and highest at the moisture level corresponding to a matrix potential of -50 centibars (Figure 3.65; Table A28). Length of navy bean roots were significantly influenced by interactions of soil type and soil moisture and interactions of soil moisture and P. penetrans (Figure 3.66; Tables A29-l-A29—4). Lengths of navy bean roots were greatest at a soil moisture level corresponding to a matrix potential of -50 centibars (Figure 3.66). Root length was significantly reduced by P. penetrans at a moisture level corresponding to a matrix potential of -5 centibars in all three soil types (Figure 3.66). Root lengths were lower in P. penetrans infected plants com- pared to noninfected plants in all three Soil types (Figure 3.66). Shoot dry weight was significantly influenced by interactions of soil type and soil moisture (Figure 3.67; Tables A30-l-A30-5). Shoot dry weights were significantly decreased by g. penetrans at all soil moisture levels (Figure 3.67A, B; Table A30-1). Averaged over soil 209 8 1. x SRNDY LORM CJ—jt H .1 A SHNOY CLHY LOHM ‘5 ET CLHY LOHM >_ __ T—- kaca @255 DJ :2 Q -41- z _: CD +— __ [E .JC3___ 23" 2: Q_ __ C3 __ o. “‘ fir ,_, l llllllll J 11111111 1 lllllJll 1 1111111] TTTTTTTII T TTTTITT] T TTTTIHI T ITTTTTTI 1' 10 100 1000 10000 MHTRIX POTENTIHL [- CENTIBHRS] Figure 3.65. Influence of soil moisture on total popula- tion densities (root + soil) of P. penetrans associated with navy beans in thfee soil types. .mucmam coon >>mc mo numcma uoou co Amv musumHoE HHOm oam mama HHOm oam .Adv mcmuumcmm .m mo huwmcmp HMHuHCH pcm musumfloe HHOm wo mcofluomumDCH mo mocmsHmcH .om.m whomHm Gui—EH. - v .2—EHE x23! 53-5.5 :3.— >5u Sim 53 323 m on R 8m 8m 2:: _. . LI 1 J 210 1'1 m LJ ("I M S 8a *1 Ilg _II II; |_ LJ r7 rn r1 r1 LJ LJ LJ LJ HJ (SJBQIJUGD -) Istnuanod XIII?” ASVEBBFRK Asvfigg m < (1105 {I3 (I)! / W11}! '1!) LUSH]! Ullflflfld Will)” .mcmmn >>mc mo unmflm3 wuv uoonm co ADV mcmuumcmm .m mo wuflmcmc HMflUflCH cam mm>u HHOm wcm Amy mcmuumcmm .m mo muflmcmn amauflcfi wan muzumfloa HHOm .Adv musumflOE HHom Ucm mama HHOm mo mcofluomuwucfi mo mocmSHmcH .nw.m musmHm Ana—Emu . . (Sum—8 =5! 211 (QWHLD ' ) 1|“th XIINH 3.. :6 :4 >5... ES :84 g m S a 8. 8m Ran ‘84 >59 34 5.3 53m 3; 53 m m flu} u a m .IJ m 1 _ fill; x$ flflw 2 m m _ All; n m HJ _II_ M. u FL _ _ m a Hl|fl\ fillJ all; 71F\‘ n m rllu FIIL‘ HIIL / / Flu rial m m w w ‘ nu mu m m 3.53.5»? .fEiE—Sfi 19:53.55.“ u m < 212 moisture levels, dry weight was significantly (P = 0.05) reduced by P; penetrans in all soil types (Figure 3.67A, C). Shoot dry weight was lowest in the clay loam soil in noninfected and E. penetrans infected plants (Figure 3.67A, C). Plant heights were influenced by interactions of soil type, soil moisture and P. penetrans (Figure 3.68; Tables A31-l-A31-5). Plant height was reduced by P. penetrans in all soil types (Figure 3.688, C). Plant heights were lower at high moisture levels and increased at moisture levels corresponding to a matrix potential of ~50 centibars (Figure 3.68A, C). Root areas of plants were influenced by interactions of soil type and P. penetrans (Figure 3.69; Tables 832-1- A32-5). P. penetrans decreased root area at all soil moisture levels (Figure 3.69A). Root area was lowest in the clay loam in P. penetrans infected plants. Yield of dry beans were influenced by interactions of soil type, soil moisture and P. penetrans (Figure 3.70; Table A33-l-A33-5). E. penetrans reduced bean yields in all three soil types at each moisture level studied (Figure 3.70). Highest yields were obtained at the soil moisture level corresponding to a soil matrix potential of —50 centibars (Figure 3.70-3.7l). Lowest yields were obtained at high soil moiSture levels corresponding 213 .mucmHm coon >>mc mo munmflmn so ADV mama HHOm_pcm wusumfioe HHOm oam .Amv mcmuumcmm .m mo wuwmcmp Hmwuflcfl oam mama HflOm .Amv mcmuumsmm .m «o >uflmsw© Hmfluwcfl can wusumfioe HflOm mo mcofluomumucfl mo mocmoamcH .mo.m ousmflm 5:253 - o 7:55.. 2:3. 34 5.5 53 :3 55 :1: 524m («3 >39 53 >59 5.3. 53 53 m S 3 :2. 8m 93‘ Ill! Iv 1H Hull. m NL UL FL m w w IllJmHmTl hell“ FJIL e m 1.1!. Ami! _1 1_ .i a m M HWIJ _ _ m Wig m Hjlu r. _ a m m HI]... _ — _ T ..l .4 riL _ — _ fl § m m n J y. 1| \.. , L o Iii?! Ham 1U. gm T m m I nJJ .1]? : JDL HIT.— 82 e a. .5.:3_U.S ill 4 :bctnzgpg .5.—S_!S u m < (“05 ‘00 MI / M11534 '3 > “Will I11"ufi~:“lllhi 214 .mHCMHm coon >>mc Mo mmum uoou co AUV mama HHOm oam wusuwHoE HHOm pawl Amy mcmuumcom .m mo wuHmcmp HMHuHcH oam mmuu HHOm .Amv mcmuumsmm .m mo muHmcmp HMHHHGH oam mnoumHOE HHOm mo mcoHuomumHCH mo mocmoncH u I I1:.8._..>5u ‘8 .Sfl 55. 116.5 17% D ID! mug m 1 3mm .. ii ...... l l mm. lqwilmwi t .: l: mu slimmwli.1 r l$;:nlmml “mu H “Waugh—xx an O u-o 8 .8. § —0 (mum ‘ ) N11810:! llllfl :8.— >59 53 So 53. .%.q!§_ Sag (“05‘ ‘U3 mt / mm '4) mam HUM WHIII S 252—hwy - o 1:53.. is»! R 8— £31.15: .mo.m musmflm (”"05 fl) 0! I mam 'd) All” GUM Tflllll .mcmmn m>mc mo pHmHm co ADP mcmuamcma .M mo maHmcmp HMHaHsH oam mama HHOw cam Amy mamaamcma .a mo maHmcmo HMHchH paw masamHOE HHOm .Adv mama HHOm oam musamHOE HHom mo mcoHaomamacH a0 mocmsHacH .o>.m masmHa Gui—53 . a 1:55; :5! 215 (8.. =3 34 id 5.3 34 g m S 3 8‘ 8m RB— 53 5.5 :43 5.3 53 3; i W... W - 1...! 1J m m FL L 3 fiJ m m TIL. mu mu NU l.— —l .5 m S— _I _l n n .1J _ d m m FLL _ _ . .. 1-1m]. _ _ _ _ alJ m m 1a .FIIL FIIIIa c a m aJL m , ilIIIHHE- «MU lfillwx m m m. a. I an NU «MU m m 3.35:5 3.2::5 Slag-«HE u m < (Will?) ’ ) NHIIIOd lll'V- 216 Figure 3.71. Influence of soil moisture expressed as matrix potential on yield of noninfected and g. penetrans infected navy beans grown in three soil types. Equations for the relationships between navy bean yield and matrix potential. Y = navy bean yield; x = matrix potential NI = noninfected; I = P. penetrans infected Sandy loam NI: Y = - 1.3430390178 + .94734232927 x - 1.03799212599 x (R2 = 0.93) I : Y = — 0.497700825489 + 1.896 0676671 x — 0.510629921261 x2 (R = 0.82) Sandy clay loam NI: Y = - 1.56876476974 + .78813577679 x - 0.999015748033 x (R2 = 0.84) I : Y = - 0.391307829268 + 1.5361323444 x - 0.388188976379 x2 (R2 = 0.94) Clay loam NI: Y = - 0.612844452488 +22.018 8376449 X - 0.532283464568 X (R = 0.91) I : Y = - 0.245989441013 + 1.09555877425 x - 0.287992125985 x2 (R2 = 0.80) 217 “mammaazmu nu :aoa >¢4u aqaazwaom mol 0— owauuaz_ Dwauuuzazoz xamaqz d v rl 3 8731A N838 A80 [lNUWd/O] .Hm.m madea ouauuuz_ ouauuaz_zoz rue; >¢4u mozam .wzqmaasz 1. oqaazwaoa xamaqz ooo_ oo_ o. C X 0131A N838 A80 (lNUTd/O) L 2:— a a a 8% b H b - h 4 b b h F: b _ _:-—«H- q :: cabana:— ouauuuzazoz Eco; rozqw mamaasz 1. oqaazdea xamaqz omm_ oo_ or 1 . llNUWd/O) 0731A N838 A80 218 to a matrix potential of -5 centibars (Figure 3.7OA,B). The relationships between dry bean yield and matrix potential were eXpressed as second degree polynomials (Figure 3.71) and the curves for these reationships ade- quately describe the relationships. In the sandy loam soil yields from noninfested plants were significantly higher than yields from nonin- fested plants in the sandy clay loam and clay loam respec- tively (Figure 3.71). The equation for yield of non- infested plants in the sandy loam soil is: Y = -l.3430390l78 + 3.94734232927 X 2 (R2 = 0.93) -l.03799212599 X where Y = dry bean yield and X = matrix potential while the equation for yield from P.penetrans infected plants from the sandy loam soil is: Y = -0.497700825489 + 1.89670676671 X - 0.510629921261 x2 (R2 = 0.82) The differences in the terms in these two equations in- dicate the decrease in yield in P.penetrans infected plants. In the sandy clay loam soil the equation relating yield to matrix potential for noninfected plants is: Y = -l.56876476974 + 3.78813577679 X -0.999015748033 x2 (R; 0.84) 219 while for g. penetrans infected plants the equation is: Y = - 0.391307829268 + 1.5361323444 X 2 (R2 = 0.94) - 0.388188976379 X Reduction in yield is indicated in the equation for yield in g. penetrans infected plants compared to the equation for yield in noninfected plants. For noninfected plants from the clay loam soil the equation for the relationship between yield and matrix potential is: Y = - 0.612844452488 + 2.01878376449 X - 0.532283464568 x (R2 = 0.91) while the equation for yield from P. penetrans infected plants is: Y = - 0245989441013 + 1.09555877425 X 2 2 - 0.287992125985 X (R = 0.80) The decrease in yield in P.penetrans infected plants is evident in the last equation and the decrease in yields in this type compared to yields from plants in the sandy loam and sandy caly loam respectively is also significant. 220 3.4.2.4.3 Effect of interactions of soil type, soil moisture and intial population densities of P. penetrans on growth and yield of navy beans and on pOp- ulation densities of P. penetrans Root population densities increased with increase in degree days up to 1407 DD 10 C and then decreased (Table A34-l). Densities were influenced by interactions of soil type, soil moisture and initial density of P. penetrans at 1056 DD 10 C (Figure 3.72; Tables A34-2- A34-5). Root densities were lowest at matrix potentials of -1000 and -5 centibars respectively (Figure 3.72A, C). Soil densities of P. penetrans were lowest at 1407 DD 10 C and highest at the end of the growth period. Densities were influenced by interactions of soil type, soil moisture and initial density of g. penetrans at 1056 DD 10 C (Tables A35-l-A35-2). Final total densities at l407 DD 10 C were lower in the clay loam at all moisture levels (Figure 3.73; Table A36-l). At 1056 DD 10 C final total densities in roots and soil were significantly influenced by inter- actions of soil type, soil moisture and initial density (Tables A36-2-A36-5). Root weight was not influenced by three-way inter- actions of soil type, soil moisture and initial density 221 .Adv mama HHOm 0cm masamHOE HHom m0 mcoHaomamacH a0 mmcmsHmcH 33» n5 R: x ‘5'! .3 mtnfl 3:158; 1.2-— .0 OH on mmoa Wm mamaamcmm .M mo mmHaHmcmp :oHa Istaoa aooa co AUV mamaamcma ha mo maHmcmp HmHaHCH oam madamHOE HHom paw .Amv mamaamamm .a a0 maHmcmp HMHchH tam mama HHOm a .... 8 . I. a 4. . i- fl rmelmTl) a . Eila L... a. :8 a \ gala; .2 >2ka 8:155; u (mum ' ) 711113104 “ll“ 3.8 m5 8— x 35'! .5 >29! 8:: 1:..— 8. a: c o “.111“ mu! 'T is g 1.1 2|.mul'lmw 3 is So I). ) W“ ML. 53 .3 g :8 w \ grit .2 553.! 8.25.5; m .325 . . 1:55; 2:! a 8 RE .Nm.m masmHm rn u FT I.J .J IH) £9! a x 32 .8 pt: 8:: < 8....“ 84»; £5! 222 .mcmma m>mc saH3 pmamHUOmmm mcmaamcma .al no A HHom + aooav mmHaHmch Hwaoa HmcHa co ADV mamaamcma .a mo maHmcmp HmHaHCH paw mama HHOm cam Amy mcmaamcma .a mo maHmcmp HmHchH paw madamHoe HHom .Amc mo aanm3 aooa co ADV Imama HHom pom madamHOE HHOm oam Amy mama HHOm pom mamaamcma .a mo maHmcmp HmHchH .Adv mamaamcma .a mo maHmcmp HmHaHCH oam masamHOE HHom a0 mcoHaomamacH mo mocmsHacH .vm.m masmHa 23.5. - . 1:55. 2:... 2.8 .6 8. \ ...-air ... EB. 5.3.6. 1:... 2.8 .5 8. . BEE. .... En... 5.5.5. 1:... 224 (“HID ' ) Vlllllm IIIIN a 82 1))! 8. 8. n o 8. a. n _ W ...... BS fur mm .13 53 k mu fill. .IJ _|l fl |m L is :3 I.) flu is =3 “HI—7 an...“ I... a... 5:6,... 1-1+ m. 5:33 a mu. 3.5.5.88 3.5.!59 2.5858 g m < 225 .o OH om omOH am macmHa cmmn m>mc mo aanmz map aoonm co AUV mamaamcma .a mo maHmcmp HmHchH oam mama HHOm oam Amy masamHOE HHom oam mama HHOm .Amv mamaamcma .M a0 maHmcmp HmHaH:H 6cm masamHOE HHom mo mCOHaomamacH mo mocmsHacH .mm.m masmHa Sada—=8 - . ...—RES :5! 2.8 .5 8. \ mafilr .... :58 8.258.. 3:: 3.8 .5 8. \ magi... .... Emu! 8:158. 1:... 8. 5. n c m a 8... .. II§-: I 8. - a o . ..I 1| _ — Li . I 5.: 5.3 ~II L IL 53 5.3 I. Iflw III I..- III {“1 LII-d 2:2 :IIIImm 5a. .353 IIIIIm F7 I.J » EH... a: C 9+“) TNFIQ I ... 2...... I: .--m..._..--B -I I . I ,w I)? ,ITIIrII ~¢.S_U§»§ .o.S_U£—§ .o.:3_!E_R!m u m < L..I (“HID - I Nlllllfid IIUIV- 226 moisture (Table A39—2). Plant height increased with increase in degree days over the growth period (Table A39-l). Plants were highest at a matrix potential of -50 centibars (Table A39-l). Plant heights were signif- icantly (P = 0.05) reduced by densities of 150 and 300 P. penetrans per 100 cm3 soil (Table A39-l). High and low soil moisture levels corresponding to matrix potential of -5 and -1000 centibars respectively reduced yield of dry beans in all soil types (Figure 3.76; Table A40-l). Interactions of soil type and soil mois- ture, soil type and initial density of P. penetrans, and soil moisture and initial density of P. penetrans, respec- tively significantly (P = 0.05) influenced dry bean yields (Figure 3.76; Tables A40-2-A40-5). Navy bean yields were significantly reduced by population densities of 150 and 300 P. penetrans per 100 cm3 soil respectively. Yields were lowest in the clay loam soil and highest in the sandy loam (Figure 3.76A, C). Highest yields were obtained at a matrix potential of -50 centibars (Figure 3.76B). 3.4.3 Discussion Soil moisture characteristic curves for the three soils indicated that percent volumetric moisture content of soils increased with increase in matrix potential. The .mcmma m>mc mo pHmHm co ADV masamHOE HHOm pcm mama HHOm oam Amw mamaamcma .m wo maHmcmp HmHaHCH oam masamHOE HHOm .A!U£ .¢.n$.>’l§ u m < 228 soil moisture characteristic curve obtained for the sandy loam is as expected for this soil type (Baver, 1956). For the clay loam, however, the soil moisture character- istic curve is slightly different from that expected and percent soil moisture associated with low matrix potentials was somewhat higher than expected (Baver, 1956). The high moisture content could be due to inadequate re— moval of water at high pressures to the thickness of the soil cores used in experimental procedures. Adjust- ments were made in calculation of soil moisture content for the clay loam soil in determining soil moisture levels for other experiments. The higher population densities associated with the sandy loam soil is in agreement with reports on nema- tode movement in sandy soils (Oostenbrink, 1966; Wallace, 1973; Norton, 1978). Nematodes live and move in the thin film of water surrounding soil particles and this move- ment is facilitated in coarser textured soils with large pore spaces than in fine textured soils with small pore spaces. Although soil moisture content is generally lower in sandy soils nematode survival is generally higher in these soils at adequate moisture levels. The higher population densities in sandy soils are also related to optimum temperatures which are attained in these drier soils in contrast to lower temperatures in 229 wetter cold clay soils. The optimum soil moisture level for survival and reproduction of E. penetrans was at a matrix potential of -50 centibars. This matrix potential corresponded to volumetric soil moisture contents of 21, 27 and 44 per— cent in the sandy loam, sandy clay loam and clay loam respectively. In general population densities of E. penetrans increased with decrease in matrix potential reaching highest densities at -50 centibars and then decreasing at lower soil moisture levels. In the sandy loam and clay loam the rate of decrease in population densities of g. penetrans was greater than in the sandy clay loam soil. This is related to the ability of sandy clay loam soils to maintain optimum soil moisture levels because of drainage. In the clay loam soil moisture content remained high even at high and low matrix potentials and reduction in densities of g. penetrans could be related to lack of oxygen which is expected under high soil moisture conditions. Kable and Mai (1968) observed similar decreases in popula- tion densities at high and low moisture levels. Townshend and Webber (1971) observed greater survival of B. penetrans at low moisture levels compared to survival at high mois— ture levels. At low moisture levels plant roots were stimulated 230 to penetrate deeper into the soil matrix to obtain mois- ture, hence the increase in root length at high matrix potentials. Plant growth as indicated by shoot dry weight was greatest at a moisture content corresponding to -50 centibars. Plant growth was generally poor at high and low matrix potentials in both noninfected and B. penetrans infected navy bean plants. This is related to the lack of oxygen in wet soils and the inability of plants to maintain their water balance due to transpiration re- quirements in dry soils. The relationship between avail- ability of soil moisture and expression of damage by g. penetrans on tobacco has been observed by Townshend and Marks (1976), who reported increased growth at high mois- ture regimes in contrast to growth at low moisture regimes. Tobacco plants infected with g. penetrans required less moisture compared to moisture requirements for noninfested plants and this is expected due to the higher growth rate of noninfested plants and greater transpiration requirements. The higher cation exchange capacity of clay soils and higher associated organic matter c0ntent should en- hance growth of plants at adequate soil moisture levels (Lyon g£_§l. 1958). However the beneficial effects of cation exchange capacity and organic matter associated with clay soils can be negated under adverse soil moisture conditions. The sandy loam soil is also an adequate soil 231 type for plant growth under Optimum moisture conditions. However rapid drainage can occur in these soils and result in soil moisture deficiencies. Nematode movement is en- hanced in sandy loam due to the suitable size of pore spaces. In the sandy clay loam and sandy loam soils it was evident that at a soil moisture level corresponding to -50 centibars an initial population density of 25 3 g. penetrans per 100 cm soil could be tolerated on navy beans without significant losses in dry bean yields. In the clay loam however yield could be reduced by this initial population density at a moisture level of -50 centibars. The need for adequate management of soil moisture in dry bean production is evident. Soil moisture influences temperature and to a large extent the functioning of plant disease and pest systems. The use of appropriate irrigation scheduling in bean production can overcome problems of moisture stress, while adequate drainage can alleviate problems associated with excess soil moisture. Use of an early planting date can also reduce problems of soil mois- ture stress. Temperatures are generally high at the time of flowering and moisture requirements are high at this period. If beans are planted early at adequate temperatures for germination, the physiological process of flowering can 232 be attained before moisture stress conditions begin. Assimilates can be transferred to the reproductive sink in the absence of moisture stress and thereby increase the probability of high yields. Therefore the choice of planting date is critical for avoiding moisture stress problems during some growth phases of navy beans. 233 3.5 Interactions of P. penetrans and Mycorrhizae Endomycorrhizae are commonly found in bean pro- duction systems, and the need to examine the significance of this component of the E. penetrans-navy bean system is important. The following studies were designed to examine the effects of Glomus fasciculatus on growth and yield of navy beans and to examine interactions of this mycorrhizal fungus and P. penetrans and the effect on growth and yield of navy beans. 3.5.1 Effect of initial population densities of Glomus fasciculatus on growth and yield of navy beans 3.5.1.1 Method The experiment consisted of a randomized design of four replicates of six treatments including population densities of 0, 10, 50, 100, 500 and 1000 spores of Glomus fasciculatus. Forty-eight 3.72 cm clay pots were filled with 3000 cm3 of sandy clay loam soil containing the desired densities which were obtained by mixing steam sterilized soil with soil containing spores of g. fascic— ulatus. Three navy bean seeds were planted in the soil in each pot. After germination plants were thinned out leaving one seedling in the soil in each pot. Plants 234 were watered daily and maintained at a temperature of 85 i 10 C in the greenhouse. Shoot fresh weight, leaf area, plant height, root weight, root area and root length were recorded after a period of 56 days of growth (517 DD 10 C). Shoot systems were oven dried and shoot dry weight was recorded. After a period of 96 days dry bean yields were taken from the remaining 24 plants and dry bean yields were recorded. Vesicular-arbuscular root infection was determined (3.1.6) and spore density of Glomus fasciculatus was determined (3.1.5). 3.5.2 Interactions of P. penetrans and g. fasciculatus and effect on growth and yield of navy beans 3.5.2.1 Method The experiment consisted of a randomized design of four replicates of four treatments including initial population densities of (1) 300 P. penetrans per 100 cm3 3 soil (2) 1000 spores of g. fasciculatus per 100 cm soil (3) 300 P. penetrans per 100 cm3 soil plus 1000 spores of g. fasciculatus per 100 cm3 soil and (4) 0 P. penetrans per 100 cm3 soil plus 0 g. fasciculatus per 100 cm3 soil. One hundred and twelve 3.72 cm clay pots were filled with 3000 cm3 soil containing desired densities of P. penetrans and g. fasciculatus, which were obtained by 235 mixing steam sterilized sandy clay loam soil with P. penetrans infested soil and soil containing spores of g. fasciculatus respectively. Three navy bean seeds were planted in the soil in each pot. After germination plants were thinned leaving one seedling in the soil in each pot. Plants were watered daily and maintained at 85 i 10 C in the greenhouse. Growth parameters of plant height, leaf area, shoot fresh weight, root weight, root area and root length were recorded at 14 day intervals over the growth period of 98 days. Shoot systems were oven dried at 30 i 5 C and shoot dry weight was recorded. Leaf area ratios were calculated (3.1.8). Soil and root samples were taken for nematode analyses (3.1.1.2 and 3.1.2.2) and P. penetrans densities were determined (3.1.3-3.1.4). Vesicular-arbuscular root infection was determined (3.1.6). Soil samples were analyses to determine spore densities of g. fasciculatus (3.1.5). 3.5.3 Results 3.5.3.1 Effect of initial population densities of Glomus fasciculatus on growth and yield of navy beans Glomus fasciculatus germinated and colonized navy bean roots (Figure 3.77; Tables A41-A42). Colonization 236 (PERCENT) D -1S.82 + 23.48 0.95 (LOC- X] ll INFECTION V A M ROOT o T I I 1 10 100 1000 G.FASCICULATUS (SPORES / 100 CM3 SOIL) Figure 3.77. Relationship between percent vesicular- arbuscular mycorrhizal root infection of navy beans and log of initial spore density Q. fasciculatus 237 levels at 517 DD 10 C ranged from 11% in plants exposed to an initial density of 10 spores of g. fasciculatus per 3 100 cm soil to 63% in plants exposed to an initial density of 1000 spores of E. fasciculatus (Table A42). The relationship between vesicular-arbuscular root infection and initial spore density of g. fasciculatus was expressed as a linear function and the relatively high degree of correlation (R = 0.95) and confidence intervals indicate that the linear relationship is appro- priate. The equation for the relationship is: Y = 15.82 + 23.48 (log X) (R = 0.95) where Y = percent vesicular-arbuscular root infection and X = log initial density of spores of g. fasciculatus, and the equation expresses the increase in root coloniza- tion.by g. fasciculatus with increase in initial spore density. Final spore densities were greater than initial spore densities of 10, 50 and 100, but lower than the initial densities of 500 and 1000 (Table A42). Shoot fresh weight, shoot dry weight, leaf area, plant height, root area and root weight were significantly increased by initial Spore densities of 100, 500 and 3 1000 g. fasciculatus per 100 cm soil (Tables A41-A42). Linear regression functions were developed to express the relationship between plant growth parameters 238 and log of initial spore density of g. fasciculatus (figures3.78-3.80). These linear regression functions adequately espressed the relationship except for the relationship between log initial spore density and root area (Figure 3.79A). The wide confidence intervals associated with this function indicated a low degree of significance. The equations fim:the linear functions indicated the increase in shoot dry weight, leaf area, plant height , root weight and root area with increase in initial spore density of g. fasciculatus (Figures 3.78- 3.80). Dry bean yield increased with increase in initial spore density of g. fasciculatus and the relationship be- tween Umse two variables is adequately described by the linear function expressed by the equation: Y = 2.15 + 0.396 (Log X) (R = 0.96) where Y = dry bean yield and X = log initial spore density of g. fasciculatus (Figure 3.81). 3.5.3.2 Interactions of P. penetrans and g. fasciculatus and effect on growth and yield of nayy beans Vesicular-arbuscular root colonization increased with increase in degree days (Figure 3.82; Table A43) and the relationship between vesicular-arbuscular root infection and degree days was expressed by second degree polynomials for plants infected with g. fasciculatus and .muanm cmmn >>mc mo Am. moum mama Ucm Ad. unmflm3 wup poonm co msumasowommm .0 mo pommmm ....m mus... 239 3.8sz 8. \ 3.83 $248.85.... 3.8 Mao-m... \ 3.5.3 824.582.... 8.: 8. o. . 8o. 8. o. . r! b b 0 r- _ _ 0 T ... 1m It 8... 0 cm... x .I _II .... .x 8... ~23 . ~58 2W. .x 8... mm... .. Emu . z jaw-d.— .. V w. E ..m.- - m1 w Imrw. 0 Q.- \\ .IO 0 m 1 9 [IO 0 (1NV1d / 9) 1H913M A80 lOOHS 240 m0 Am. unmflw3 noon pcm Ad. mwum noon :0 msumasuflommm .0 mo pommmm .mucmHm cams >>mc .mn.m musmflm ...om so so. \ mumoam. m=.<.:o.um ---- .i a “M 3 ..vmw l. ... \l 9 9 I. [I d 1 .I V N ..enw m I ...om so so. \ mmmoamv m=.<.=o.um- .- Z < 35' >_ -a Y = 2-15 + 0.395 (LOG X) m“ a R : 0.95 c: I I I I 10 100 1000 G. FASCICULATUS (SPORES / 100 CM3 SOIL) Figure 3.81. Effect of g. fasciculatus on yield of navy beans. 243 mcmuumcmm .m mafia msumasowommm .0 can msumauoflommw .0 mo mocmsHmcH I .poflumm buzoum may um>o Amy mnpmHsoflommm .0 mo mofluflmcmp macaw so can .4. muoou cmon >>mc CH cofluommcw Houflnuuooms umstmDQMMIumasommm> mo McmEQon>m© co .Nm.m mnsmflm oom— — wjfiao. w>¢o wmmdmo ompcnzzsuum com. oam owe 0mm bIIr b ? * P 5 LI LI P .mw tzOJO + wzampmzwm .m 0 .mm wszonc G 63 1 1 I ' I 009 003 009 fi r 008 (1103 2ND 00; / SBHOdS) snlv1nolosva'9 ... SOD. w>¢o mumomo dwpcbnznuuc 8m. 8m. 8m 8.. com on F I _ p P I . p p . z 10 v 10 9 in. Y 8 .10 ...m maze-a . 9.5.82”... ... o--. < ...m was... I . m 0 (1N3383d) N01133:.INI 1008 H B A 244 g. fasciculatus plus 3. penetrans (Figure 3.82). Vesicular- arbuscular root infection was reduced in plants infected with both E. penetrans and g. fasciculatus compared to plants colonized with only g. fasciculatus (Figure 3.82A). The equation for the relationship between vesicular— arbuscular root infection and degree days in plants exposed to only g. fasciculatus is: Y = -23.5352315148 + 0.167913586149 X 2 - 0.00007271347219 x (R2 = 0.96) and for plants infected with both E. fasciculatus and g. penetrans the equation for the relationship is: Y = -22.5500367928 + 0.145471967184 X 2 (R2 = 0.95) - 0.0000643638763 X the high degree of correlation indicated by the R2 value indicates that the relationship is adequately described by the second degree polynomial function. Mycorrhizal spore density associated with soil initially infested with only g. fasciculatus was signif- icantly (P = 0.05) higher compared to densities associated with soil infested with both 9. fasciculatus and P. penetrans (Figure 3.82B; Table A44). Spore densities fluctuated throughout the growth period, and final spore densities were higher than initial spore densities of Q. fasciculatus (Figure 3.82B). Population densities of P. penetrans were higher 245 in plants infected with only 2. penetrans at the beginning of the growth period. After 56 days (715 DD 10 C) pop- ulation densities were higher in plants infected with both g. penetrans and Q. fasciculatus (Figure 3.833). Two maxima in population densities were observed at 343 and 603 DD 10 C respectively. Densities reached a max- imum at 603 and remained relatively constant at these densities until 965 DD 10 C in plants infected with only P. penetrans. A similar trend was observed in plants infected with both P. penetrans and g. fasciculatus except for a slight increase in densities between 603 and 965 DD 10 C (Figure 3.83A). Total densities in roots plus soil followed a similar trend except for a leveling off of densities in the presence of both P. penetrans and g. fasciculatus (Figure 3.83). Growth parameters of shoot fresh weight, shoot dry weight, leaf area, plant height, root weight, root area and root length were significantly (P = 0.05) in- creased by colonization with g. fasciculatus (Tables A45-A51). Dry weight of plants infected with both g. penetrans and g. fasciculatus were significantly higher (P = 0.05) compared to plants colonized with only g. fasciculatus after 14 days of growth (185 DD 10 C) (Table A46). There were no significant (P = 0.05) differences in dry weight and leaf area in plants infected with 246 l ll'l'l'll ll}! .>H0>fluoommmu msumasuflommw .m moam mamuchwm .M van mcmuumcmm .m pomomxm mcmmn >>mc nufl3 pmumHUOmmm mcmuumcmm .m mo moHEmcmp cowumasmom .mm.m musvflm .useo. w»¢o mumomo om.¢4323uu¢ .uaoo. m»¢o mmmomo ow.¢.:z:uu¢ com. com. o¢m owe own no com. com. 0mm owm oam — b . h t b p r p I F p I b I L t b b p I I 001 1008 0+7108 N3 OOI/SNU813N38'8 V I 002 I DOE I 009 j I 008 .mw macabo + wzcxpmzum .m 0 .mm monomo + mzcmpmzmm .m 0 wzmmpmzmm .m 9 I wzcmpmzwm .m G r 009 00: 002 002 001 1008 0 / SNUHIBNBd 'd 009 009 247 g. fasciculatus plus g. penetrans, compared to controls after 14 days of growth (185 DD 10 C) (Tables A46-A47). P. penetrans significantly (P = 0.05) decreased all growth parameters (Tables A45-A51). Root area was lowest in plants infected with 3. penetrans and highest in plants colonized with g. fasciculatus. Root area increased throughout the growth period reaching maxima at 715 DD 10 C and then decreased after this period (Figure 3.84). The relationship between root area and degree days was expressed as second degree polynomial functions (Figure 3.85). For control plants the equation for the relation- ship is: Y = -3.40464028328 + 0-0552470297167 X - 0.000037776936613 x2 (R2 =o.90) The increase in root area in plants infected with g. fasciculatus was evident from the equation for the relation- ship between the two variables: Y : —6.60066024855 + 0.0974171382959 X - 0.00006676630977 x2 (R2 = 0.87) and the decrease in root area in plants infected with g. penetrans is observed in the equation for the relation- ship between the two variables: Y = -1.760739383 + 0.0386747170543 X - 0.00002693062666 x2 (R2 = 0.92) 248 C3 ¢ CONTROL VI *6 P. PENETRRNS . 0 GLOMUS SP. [3 P. PENETRRNS + GLOMUS SP. I_\ o— N to Z (_J 0. CE 00 LLJ Of. G: . I_. C) O CD-I Q: v—c u// d \u' C) ' I I I ‘ I ' I ' I 0 300 600 900 1200 1500 RCCUMULRTED DEGREE DRYS [DDmc] FIgure 3.84. Influence of P. penetrans , G. fasciculatus and P. penetrans plus G. fasEiculatus on root area of navy bean—plants over the growth period. 249 Figure 3.85. Relationship between root area and degree days of noninfected plants and navy bean plants infected with P. penetrans (A), g. fasciculatus (B) and P. penetrans plus G. fESCiculatus - Equations for the relationships between root area and accumulated degree days at base 10 C Y = root area, X = accumulated degree days base 10 C. Control (noninfected) y = -3.40464028328 + 0.35524702 7167 X -0.000037769366l3 X (R = 0.91) P. penetrans y = -l.760739383 + 0.0386747170543 x -0.00002693062666 x (R2 = 0.92) Glomus fasciculatus Y = -6.60066024855 + 0.0974171382959 x -0.00006676630977 x2 (R2 = 0.87) P. penetrans + g. fasciculatus Y = -0.773505254102 + 0.94334717 572 X -0.000029999ll8087 X (R = 0.94) .mm.m 0058.0 250 ...-So. wt... HERE SEE—1.8.... 8... 8o 8% com —I . » in was... . 32.55.. ... oi U 32:23 I. a San. wEo umxouo am..a...::oua 8m. 2.... 2.... own ...:no. 2mm ammo-“E ou.c...z:..-.a 8w. 2.... emu 2.; OI oz §I ' (1H3 I U3UU 1008 I m ...m 2.5.... o... .2:on I 02 01 ("”3 J U385 1008 DE 1 2.5.5:... .. o... d. .8523 I DI 8388 1008 1 SI l 03 (1H3 ) v 251 Leaf area ratios of plants fluctuated throughout the growth period (Figure 3.86) and were highest in plants infected with g. penetrans and lowest in plants colonized with g. fasciculatus. Dry bean yield was significantly (P = 0.05) in- creased in plants colonized with g. fasciculatus (Figure 3.87). There was no significant (P = 0.05) difference in yield of dry beans from control plants compared to plants infected with both E. fasciculatus and P. penetrans. 3.5.4 Discussion Beneficial associations between g. fasciculatus and navy beans resulted in increased growth and yield in mycorrhizal bean plants. Spore densities above 50 g. fasciculatus per 100 cm3 soil significantly increased growth and yield of navy beans. The adverse effects of g. penetrans on growth and yield of dry beans can be minimized by the presence of mycorrhizal associations between navy beans and g. fasciculatus. The mode of action and the function of the fungus in interactions with P. penetrans and navy beans is unclear. Population densities of P. penetrans were not significantly (P = 0.05) different in plants infected with g. penetrans compared to densities in plants infected with both P. penetrans and G. fasciculatus, therefore the mode of action 252 g1 a CONTROL x P. PENETRRNS - 4 o GLOMUS SP. N: 03 P. PENETRRNS + ‘-’ E4 GLOHUS SP. 0 '1 ..— CI: 8- m c—c CI 4 LLJ I. CE (3.... L1. L0 C]: In.- __I C) I I ' I ‘ I ' I ' I 0 300 600 900 1200 1500 RCCUMULRTED DEGREE DRYS (0010 c] Figure 3.86. Influence of P. penetrans, G. fasciculatus and P. penetrans plus G. fasciculatus on leaf area ratio of navy bean plants over the growth period. 253 gIv‘ g? a z \ 2 F3 4 g o "’ g 4 z a z >— N‘ ¢ 2 / °= - z 36’ z :2 ~ g o z / / o 0 0L PP PP+GL TRERTMENT Figure 3.87. Influence of P. penetrans, G. fasciculatus and P. penetrans plus g. fasciculatus on yield of navy beans. 254 of the fungus was not related to reduction of population densities. Reports indicate that interactions of nematodes and mycorrhizal fungi are complex (Fox and Spasoff, 1972: Baltruschat, 1973: Schenck and Kinlock, 1974: Schenck gt 31. 1975). In some reports increases in nematode pop- ulation densities*wereobserved and this could be related to the increased food source provided by the larger healthier root system produced by the beneficial symbiotic association of the plant and mycorrhizal fungus. Decreases in population densities in the presence of mycorrhizal associations suggest an antagonistic interaction between fungi and nematodes. Reports on increased growth of plants in the presence of mycorrhizal fungi, contribute the increased growth to increased nutrient availability. It has been hypothesized that the fungus transfers the nutrients to the plant through a symbiotic relationship (Gray and Gerdemann, 1967; Rhodes, 1976). The exact mechanism by which phosphorus is transferred is unknown however, Tinker (1975) proposed that bulk flow and cyclosis are involved in the translocation of phosphorus from the fungi to the plant. The beneficial effects of mycorrhizae are influenced by soil fertility and is promoted in soils of low fertility in contrast to soils of high fertility (Tinker, 1975). 255 The presence of certain species of mycorrhizae in navy bean production systems can be considered as a beneficial phenomenon, and maintenance of Optimum densities of beneficial mycorrhizal fungi should be incorporated into management strategies in navy bean production. The influence of pesticides on mycorrhizal associations should be considered in development of nematode control strategies. Various reports indicate that pesticides influence mycor- rhizal populations and associations (Nesheim and Linn, 1969: Kleinschmidt and Gerdemann, 1972; Bird gt_§1. 1974; Backman and Clark, 1977; Bailey and Safir, 1977). The integration of mycorrhizal fungi as a nema- tode control strategy in management of navy bean production systems is dependent on the species of mycorrhizal fungus. The nature of the indigenous species must be determined and the effect of introducing other species should be evaluated before recommended strategies can be developed. Where the beneficial mycorrhizal species is not indigenous it can be introduced by first propagating plants in soil infested with the species in the greenhouse and transferring these plants to the field (Khan , 1972; 1975). In the field population densities of mycorrhizal fungi can be increased by effective crop rotation with plants inoculated with the desired beneficial mycorrhizal species. 256 3.6 Rotation Crops - Kidney Beans 3.6.1 Susceptibility and control of P.penetrans Egsociated with five dry bean varities 3.6.1.1 Method Five dry bean varieties were planted in a random— ized block design of five replicates of plots treated with aldicarb (Temik 15G) for control of P. penetrans and five replicates of plots containing initial densities of 116—134 B. penetrans per 100 cm3 soil. Each plot consisted of four rows 6.1 m in length and 0.9 m apart. Aldicarb was applied in 0.2 m bands at the time of planting on June 5, 1979 (207 DD 10 C). The dry bean cultivars used were Sanilac, Seafarer and Tuscola navy beans, and Montcalm kidney and Charlevoix kidney beans. Soil and root samples were taken for nematode analysis at six intervals during the growing period. Population densities of g. penetrans were determined (3.1.1.1 and 3.1.3.2; 3.1.3-3.1.4). The two center rows of each plot were harvested on October 25, 1979 (1281 DD 10 C), and dry bean yield was recorded.. 3.6.2 Results 3.6.2.1 Susceptibility and control of P.penetrans associated with five dry bean varieties Population densities of P.penetrans fluctuated throughout the season, and two maxima in densities were 257 associated with Sanilac navy beans and Montcalm kidney beans (Figure 3.88). Lowest densities were associated with Charlevoix kidney beans and Seafarer navy beans (Figure 3.88; Table A52). Densities associated with Montcalm Kidney beans decreased towards the end of the season in contrast to an observed increase in densities associated with other varieties at similar growth periods (Table A52). Aldicarb (2.0 lb per acre) was effective in reducing population densities of P. penetrans associated with all five varieties (Figure 3.88B; Table A52). Aldicarb was effective in maintaining population densities of P. penetrans at low densities throughout the season (Table A52). Yield of dry beans were significantly (P = 0.05) higher in plots with low densities of P. penetrans obtained through treatment with aldicarb compared to yields from plots with high densities of P. penetrans in the absence of nematode control inputs (Table A52). 3.6.3 Discussion Sanilac, Seafarer and Tuscola varieties were highly susceptible to P. penetrans. Seafarer appears to be less susceptible than Sanilac variety. Montcalm Kidney beans were highly susceptible to P. penetrans and maintained high densities of P. penetrans. This indicates that rotation 258 mcmuumcmm .m mo Houucoo 0cm Adv mcmnuocmm .m 00 mowEmc>0 cofiumHsaom I .mmfluflum> cmwn mac m>flm nufiz wqumOOmMM mcmuuwcmm .m mo Houucoo Dom meofiUHm mo uzmcfl cw sufiz .mm.m 0028.8 nine. m>¢o mumwmo 05.8.5230”... taco. w>¢o mmmumo omE-Szauuc com. . oam. com com com com. cow. oam com com o P t p F b . _ L . b . r E . b I. FI I p L _ p . F L L L . I 10 .d no 1.. .8 3 3 $2.... .83....5 a W. H W. 6.8:. 58.2.... + M H m 582: 4. 1w wmIIuNu ...”...ESW a 0N. 0N. 83.2% x m I 0 no II no 3 II 3 N ...I Hm .. H e 19 ”HIS 00 ..I00 01 01 ..I ~I m. 32.... 82.3.3.5 a I m. 8 $22.. 58.2.... + H 8 0 0 0 38m... 4 mn 0 I... m Ema-...... a H I... m 85.2% ... Ed D D 259 of navy beans with Montcalm kidney beans could lead to increased densities of P. penetrans and greater reduction in yields in susceptible navy bean varieties. Lower population densities of P. penetrans were maintained on Charlevoix kidney and this variety is a more suitable choice for rotation in a nematode control program for navy beans. 3.7 Comparison of Population Dynamics of P. penetrans Associated with Navy Beans Over Two Growing Seasons Because of changes in environmental conditions over periods of time, variations in seasonal patterns of population dynamics may occur from year to year. This study was designed to compare population dynamics of P. penetrans associated with navy beans in 1978 and 1979 navy bean growing seasons in Michigan. 3.7.1 Population dynamics and control of P. penetrans associated with navy beans in 1978 3.7.1.1 Method Six replicates of navy beans cv Sanilac were planted in a randomized block design on a sandy clay loam soil at Michigan State University Montcalm exper- imental farm. Six replicates of seven nematicide 260 treatments were included for evaluation for nematode control. Each plot consisted of four rows 6.1 m in length and 0.9 m apart. Three fumigant nematicide treatments of Di (2-chloroi30propyl) ether (Nemamort BB) were applied in-row 19 days prior to planting. The nonfumigant nema- ticides were applied (in-row) at the time of planting on June 21, 1978 (171 DD 10 C). Soil samples for nematode analysis were taken prior to the application of soil fumigants and at the time of planting. Soil and root samples from treatments were taken at six intervals during the growing season (3.1.1.1 and 3.1.3.2; 3.1.3- 3.1.4). The center two rows of each plot were harvested on October 20, 1978 (1301 DD 10 C) and the yield of navy beans recorded. 3.7.2 Population dynamics and control of P. penetrans associated with navy beans in 1979 3.7.2.1 Method Five replicates of navy beans cv Sanilac were planted in a randomized block design in a sandy clay loam soil at Michigan State University Montcalm experimental farm. The average initial density was 116 P. penetrans per 100 cm3 soil. Five replicates of seven nematicide treatments were also included for evaluation for nematode 261 control. Each plot consisted of four rows 6.1 m in length and 0.9 m apart. All nematicide treatments were applied in 0.2 m bands at the time of planting on June 5, 1979 (207 DD 10 C). A foliar oxamyl (Vydate L) spray was applied three weeks after planting (392 DD 10 C). Soil and root samples were taken for nematode analysis (3.1.1.1 and 3.1.3.2; 3.1.3—3.1.4) at six intervals during the growing season. The two center rows were harvested on September 21, 1979 (1221 00 10 0). 3.7.3 Results 3.7.3.1 Population dynamics and control of P. penetrans associated with navy beans in 1978 Three maxima in soil and root population densities of P. penetrans were observed during the growth period (Figure 3.89). Root densities were highest at 1044 DD 10 C and decreased towards the end of the season (Figure 3.89B). The highest percentage of the population cohort consisted of females at all sampling periods (Table 3.14). The percentage of males were three times lower than that of females but was higher than that of other life cycle stages. The percentage of fourth stage juveniles increased and was higher at the end of the season than at the initial growth period at 300 DD 10 C (Table 3.14). Iiililill I .mnma 0cm whoa ca mcmwn >>mc cue? pmuwHUOmmm mcmuuwcwm .m mo mOHEmc>© codumasmom .om.m wusmflm 262 Huang. w>¢o mumouo oukcqnzzuuc .9300. w>¢o wmmomo omhmJazjuuc Dow. DON" com com com 0 com. DON. com com com o — hr 1' r P P h b P b + P nu II — by b F b F b DI P p + F F b b B I L- .d mm d d I... . 3 “n N ”V18 13 03 OIL N HO 3 ...—u II I. N I] 8 S ”U II N / 1: S unl/ 10 “HID 00 00 0 3 0 ml 1! 0 S I. 0 ..I I. 1' 1 ...-m. 3 mm 1 ...-m. a I mbmfi X MfiIW mhmfi * m 0 0 263 Table 3.14 Dynamics of the pOpulation cohort of P. penetrans associated with navy beans in 1978. Population cohort (percent population) DD 10 c F M 2nd 3rd 4th 300 60.6 18.0 6.6 6.5 8.2 495 48.0 17.6 15.5 6.8 12.1 700 59.1 20.4 8.6 3.3 8.5 1044 56.3 16.6 11.9 5.6 8.6 1205 50.9 17.5 7.0 5.3 19.3 1272 45.7 17.2 19.8 7.8 9.5 1301 44.6 17.9 7.1 5.4 25.0 F = female M = male 264 Population densities were reduced by all nema- ticide treatments (Table A53). Soil and root densities of P. penetrans remained relatively low throughout the growing season in plots treated for nematode control (Table A53). Navy bean yields were significantly (P = 0.05) increased in plots treated with aldicarb for nema- tode control. Yields were significantly (P = 0.05) re- duced in plots treated with Di.(2-chloroisopropyl) ether (Nemamort 8E) at 36 lb per acre (Table A53). 3.7.3.2 Population dynamics and control of P. penetrans associated with navy beans in 1979 Two maxima in root population densities were observed (Figure 3.89; Table A54). Root densities of P. penetrans increased reaching an initial maximum at 636 DD 10 C and then decreased until 872 DD 10 C. Another maximum in population densities was attained at 966 DD 10 C (Figure 3.89; Table A54). Soil population densities of P. penetrans fluctuated throughout the season decreasing rapidly during the early part of the season as nematodes entered the roots and later increasing towards the end of the season as nematodes migrated from decaying roots (Figure 3.89). Population densities of P. penetrans were decreased with an input of aldicarb for nematode control (Table A54). 265 Aldicarb at 0.5 lb per acre did not significantly (P = 0.05) reduce population densities throughout the season (Table A54). Root population densities were significantly (P = 0.05) decreased by treatments of oxamyl at 1.0 lb per acre and oxymal at 1.0 lb per acre plus a foliar oxamyl spray (Table A54). Comparison of population densities in untreated plots over 1978 and 1979 navy bean growing seasons indi- cated some differences in the population dynamics of P. penetrans over the two different growing seasons. Three maxima in soil population densities were observed1111978 in contrast to two maxima in soil densities in 1979 (Figure 3.89). While soil densities of P. penetrans decreased at the end of the growing season in 1978, densities increased at this time in 1979. Soil and root population densities were higher in 1979 compared to densities in 1978 (Figure 3.89). Three maxima in root population densities were evident in 1978 and 1979 (Figure 3.89). In 1978 P. penetrans densities decreased after the Imvdmum at1044 DD 10 C, while in 1979 densities increased after the first maximum at 636 DD 10 C reaching another peak at 966 DD 10 C (Figure 3.89). The growing season was shorter in 1979 compared to 1978. In 1979 dry bean yields were significantly higher in plots treated with aldicarb at rates above 0.5 lb per 266 acre (Table A54). Yields were also higher in plots treated with oxamyl at 1.0 lb per acre plus a foliar oxamyl spray at 1.0 lb per acre. 3.7.4 Discussion Population densities of P. penetrans fluctuated throughout the growing season on navy beans. Soil densities generally decreased early in the season as nematodes entered roots and then remained relatively low throughout the season. P. penetrans is an endoparasite and the low soil densities are expected. Soil densities increased towards the end of the season as nematodes migrated from decaying roots. Control of P. penetrans was obtained with inputs of aldicarb, at rates above 0.5 lb per acre. Oxamyl was also effective in controlling P. penetrans. While Di (2- chloroisopropyl) ether offered some degree of control phytotoxicity was evident as indicated by the lower yields obtained with the application of this input. Phenamiphos was also effective in controlling P. penetrans but use of this input also resulted in some degree of phytotoxicity. The need for development of more cultural and biological methods for control of P. penetrans associated with navy beans is evident. Research on biological control of P. penetrans is limited and should increase in the 267 future (Ramaro, 1972; Saka, 1975). The choice of varieties tolerant to P. penetrans should be examined in conjunction with the economics of production of chosen varieties. 4.0 GENERAL DISCUSSION 4.1 An overview of the Research Findings Research findings indicated that Pratylenchus penetrans was found in 68% of Michigan bean fields. This nematode species was pathogenic to navy beans and signifi- cant decreases in yields of navy bean resulted in the presence of P. penetrans at densities above 25 per 100 cm3 soil. Varieties which were tolerant to P. penetrans were identified. Temperature, soil type and soil moisture significantly influenced the pathogenic relationship between P. penetrans and navy beans. Mycorrhizal associations with navy beans also influenced the development of the root- lesion disease on navy beans. Kidney beans were also susceptible to P. penetrans. Population dynamics of P. penetrans varied over two navy bean growing seasons. 4.2 A Conceptual Model of the P. penetrans-navy Bean system based on Research Findings A model of the P. penetrans navy bean system was developed, based on research findings (Figure 4.1). In this research study the interacting components of mycorrhizae and other crops grown in rotation with navy beans were exam- ined. The approach to this study however, indicated a 268 269 Tempera- ture Pra len- Cus etrans Soil Moisture Research Economic analyses Management Figure 4.1. Components of the P. penetrans - navy bean ecosystem. Components studied are enclosed in bold lines (A). Other interacting components are enclosed in dotted lines (B). 270 number of other interacting components. The model indicates that navy bean production is influenced by P. penetrans. The relationship between this crop and pest is influenced by environmental factors of temperature and moisture (Figure 4.1). Interacting components of mycorrhizae and other crops grown in rotation with navy beans also influence the patho- genic relationship between P. penetrans and navy beans. The development of effective management strategies requires detailed examination of the research findings, and economic analyses of control strategies. The research findings indicated that population densities of P. penetrans were lowest at low temperatures. This indicates that plant- ing dates should be considered as a control option if possible. Low temperatures are generally associated with early planting dates, and choice of early planting dates which are suitable for adequate germination of beans could reduce the yield loss of navy beans, as percentage yield loss is proportional to the initial P. penetrans density. Control of soil moisture is another management input which was identified. The detrimental effects of P. penetrans are emphasized under soil moisture stress or in the presence of excess soil moisture. The incorporation of been varieties which are tolerant to P. penetrans should be included in control programs. 5.0 SUMMARY AND CONCLUSIONS Pratylenchus penetrans occurs in an aggregated type distribution in the field. This therefore requires that analyses of data involve suitable transformations which assist in normalizing data. The log transformation is recommended or log plus a constant when data contain zero values. Pratylenchus spp. were present in bean fields in Michigan and high densities were associated with sandy soils and Kidney bean varieties. Tylenchorhynchus spp. were also associated with dry beans, and future research on the effect of this species on navy beans is necessary. The predominant Pratylenchus spp. was P. penetrans and this species is generally considered the most economically important species in this genus. Pathogenicity studies indicated that this species was detrimental to growth and yield of navy beans. The response to infection by this species varied depending on the bean variety. Studies indicated that varieties of Sanilac, Seafarer and Tuscola navy beans and Montcalm Kidney beans were highly susceptible to P. penetrans, while Saginaw, Gratiot and Kentwood navy bean varieties were tolerant to P. penetrans. 271 272 The pathogenic relationship between P. penetrans and navy beans was influenced by temperature. Growth and yield of navy beans were reduced at temperatures of 15 and 30 C respectively. Optimum growth and yield were obtained at a temperature Of 25 C. Population densities of P. penetrans were also influenced by temperature. Den- sities were highest at 25 C indicating maximum reproduction and survival at this temperature. Densities were lower at 15 and 30 C respectively, indicating lower reproduction or higher mortality. Interactions of soil type and soil moisture in- fluenced the develOpment of the root-lesion disease on navy beans. Optimum growth and development of P. penetrans was Obtained at a soil matrix potential of -50 centibars. Population densities of P. penetrans were higher in the sandy loam and this is expected as movement and activity of nematodes are promoted in sandy soils due to the presence of large pore spaces and more favorable temperatures. Growth and yield Of beans were generally poor in the clay loam and this was due to the large volume of water retained by this soil type with its numerous small pore spaces and great water holding capacity due to slow drainage. Growth and development of beans were decreased at high and low moisture levels corresponding to matrix potentials of -S and -1000 centibars. Population densities of P. penetrans were 273 decreased at these two moisture levels. The importance of adequate management of soil moisture in bean production was demonstrated. The detrimental effects Of P. penetrans on navy beans were minimized in the presence of mycorrhizal asso- ciations Of g. fasciculatus and navy beans. Growth and yield Of navy beans were increased by mycorrhizal asso- ciations of g. fasciculatus and navy beans in the absence Of P. penetrans. The exact mechanism of the interaction of g. fasciculatus and P. penetrans is unclear and further research in this area is necessary. Considering aspects of control choice of rotation crops should be carefully examined. The maintenance of low densities of P. penetrans at low temperatures indicate that choice of planting dates corresponding to temperatures high enough to allow adequate germination but low enough to maintain low densities of P. penetrans is advisable. Choice of early planting dates is also recommended for preventing problems associated with moisture stress at mid-season. While control of P. penetrans was Obtained with a management input of aldicarb, the use of the input should be examined from economic feasibility studies. The use Of all control inputs should theoretically be economically 274 \ analysed. However the use of economic thresholds as a decision criteria in control programs is not always feasible because of the difficulty associated with assigning monetary values to control inputs such as planting date, and crop rotation. The model indicates that continual updating of the research on this system is necessary to maintain control of P. penetrans. The research findings contribute to the understanding of the P. penetrans-navy bean ecosystem. The studies on the behavior Of this system and the effects Of interacting components provide information for development of manage- ment strategies for control of P. penetrans in bean pro- duction. While the research study addressed effects of environmental parameters of temperature and moisture and interacting components of mycorrhizae and Kidney beans, more detailed studies on other components such as insect Essay bacteria, fungi, other nematodes and other crops grown in rotation with navy beans are necessary for a more comprehensive understanding of the pest-crop ecosystem, and for development of more effective management of P. penetrans in bean production systems. These data should be adequate for simulation of a model of the P. penetrans- navy bean system. It would be essential however to vali- date such a model under varying field conditions in bean production. This model could then be used for development of management strategies. APPENDIX 275 .umou omcmu maaauaze d XHDmem< o.0 wasmx caEkmz acmcsum Oz» 0» 0c.wuooom Amo.o n a. ucmuOuuac %~ucmofiudcm.m be: one Am.uouu0a menu on» >2 UOBOHHON acumE CESHOU oh.om om.0m Oo.om Um.0m On.m~ no.0m pm.m~ 0m.m~ co.om cm.o~ on~.mH Um.na n~.h no.5 ooozucox nm.- nv.- no.- OH.- Om.om n~.H~ Oo.o~ Om.o~ unm.MH onv.ma ch.oa onv.~a nm~.o Om.w 3mcaomm no.H~ nm.H~ n~.H~ nm.HN n>.om n~.H~ O~.ma Ov.ma Om.m~ cv.vH onm.ma nh~.HH nmm.v nom.v quunu0 na.mH Om.mm Om.ma Om.om an.mH pv.a~ OH.vH cm.m~ n~.HH co.oH Om.m oam.MH nam.m na.o uaoomsh ano.va now.~m mm.vH am.~m am.vH onm.- nmo.m~ Ov.am co.m Om.mH ma.m on~.~a OH.v amo.m ucuuuuom no.ma nv.q~ mm.va OH.¢~ mo.vH Om.m~ mm.- o~.- co.a OH.O~ mo.m ono.HA m~.v no~.m omaacmm .so. uem.o: u:m.e omH o om. o - oma o omH 0 cm“ 0 cm. 0 cm. o ...Om mEo ooH\mcmuuocOm .M. >uwmcou acqumasaoa HOMuACH omma mooa mama baa Nvo mwv mom .mOmoa. m>mv wouowv vmuoasfisuud .mmeumwum> anon >up xam mo Davao: co mcmuumcum mscocmaxumum no vacuum 02% "H4 manna 276 nasmx :88302 ucoosum may 0» mcapuooom amc.o u a. ucouwuuac >aucmuauacmam uoc mum amvumuuwa 080m 0:» .umwu oocnu oamauaOE >n 0030aaow mecca :Esaoo 0mm.a coh.a nwo.~ non-m 0v».m 050.0 Omb.v Omh.v me.m cmv.m amo.~ flaw-m nw¢.a amm.a voozucox onmm.o unva.a nam.~ nav.~ nwo.v nea.v flown.m 00mm.m oncw.~ onvv.N nmo.~ nmo.~ nem.o nom.c anaomm unmo.a Ov~.a nwo.~ Dam-N ama.v nvm.v Ooe.m Omw.m onmh.~ no~.~ DON-w ama.N www.o unm.o acauuu0 nmm.o cao.a mfiata ama.m amm.~ oven.m n-.~ unam.v nm~.a Ovm.~ Oma.a nmn.N uvo.a umo.a naoonna Ohm.o nom.o mmo.a amm.~ mma.~ onnm.v amm.a 00¢.m m>~.a onmv.N umm.o Ama.~ nmh.o umm.o u0u6unom cmm.c onmm.c weo.a n-.~ Om~.~ onom.v nmvm.a 00m.m mma.a unan.~ 8mm.o nwo.~ umm.o oam.o onaacom Aucmam\0. unmamz uoom oma o oma o omw- o o oma o oma o oma o .aaON nEo ooa\m:muumcmm .a. >uamcmc ceaumasaoa amauaCH omma mooa mama 5mm mvo mmv mom anemoov axon wwuwoc vmumasfiaouc .mwauwaum> camp hep Xam mo acmaoz uoou co mcmuumcom manocmawumum uo acmuuo One .~< manna ..mO. 30cc» oaaabase masox caE3oz acccaum 0:0 (1 acapucooc .mc.o u a. accumuuap >auccuauacoam uoc Ohm am.umuuva 08mm on» xn flozoaa0u mcwoe cEanu 277 cco.ma_ an.c__ £h¢.c- nun-mwm puo~.~mn coo-Omv Una.wan unm~.oaw uOQm.mha umov.mwa 03mm.mh ooo.om vvoh.wm mpav.vm GOOJucvx news-mv neam.he 2c ~.mva ncom.nv_ unca.mm~ OUvm.0am nmc.~a~ Dam-CNN on~0.h0a owh.oaa nemm.wm onmm~.oo conovv.0n wcvnha.vv 3mcavum zme.mm n.o.vc scam.~na beam.maa ccb~5.aaa coao.nsn Obeo.ov~ Own.m- aca.~ma oca~.~ma o~o.wv m-.ov cmn.m~ cmv.m~ uoaumuo :_v.vm Omp.vc Ova-cc new-ox. ncm~.na~ ccam.mma cco.moa Obvm.mo~ bemv.oo uOm~.ana oom.vv unavw.mo 000nm s? eho.oo uaounse ass-ma are-me www.mm new-cc. cmv.ona Obno.vo. umo.vaa on-.amw mom.ah vma.mma ohm.ov oncoa.m¢ unamw.o~ onm-.vn Honouwmm cmc.- baa.no com.en ama.eo~ na~s.va~ cOm~.~mn mam.mma onmv.nv~ uao.mh 0m.vva Unma.hh 983m.mw noon.m~ onmbo.~n uaaacam ~60 mono mama i 2..-! .-Ieith. e... e I am. e e... e em. e om. p e... e .3225 .aaOm .Eo ooa\mccuuocoa .a. >uancoc coauwasaom amauaca coon ...-eaI-I I- I: 3.: ...-2 2... m3. ...... ...... aucmOO. m>mu emuvoc kuuaseaoo< .mwaucauc> coon >00 xam mo none mama co mcmuuwcmm mszocoamuuum no vacuum one .n< «anus 278 Table A4-1: Influence of initial population density of P. penetrans on root population dynamics Of P. penetrans associated with navy beans. INITIAL POPULATION DENSITY/100 cm3 SOIL O 5 10 20 40 80 160 320 DDID C Population Density/P. penetrans/g root 254 De 2a 3a 5a 12a 33b 47c 59c 341 0a 2a 6a 9a 20b 39c 85d 999 434 0a 3a 13ab 19ab 23b 53c 94d 132e 523 0a Sb 19ab 29bc 44c 113d 149e l69f 603 0a 8a 193 19a 20a 83b 115c 123c 688 0a 18a 30a 34a 37a 137b 192c 215C 782 0a 8a 15a 49a Sa' l60b 292C 309C 865 0a 17ab 38ab 58ab 80ab ll7b 332C 333C 967 0a 9a 29a 45a 65a 154b 208b 218b 1094 0a 3a 14a 20a 453 127b 168C 183C 1305 0a 2a 8a 12a 28a ll4b 115b 143b The row means followed by the same 1etter(s) are not significantly (P - 0.05) different according to the student Newman Keuls multiple range test. Table A4-2: Influence Of initial population density of P. penetrans on soil population dynamics of P. penetrans associated with navy beans. 3 INITIAL POPULATION DENSITY/100 cm SOIL 0 5 10 20 4O 80 160 320 DDloc: Final Population Density/100 cm3 soil 254 0a 23 5a 5a 29a 38a 75b 140c 341 0a 3a 4a 5a 7a lOab 13ab 19b 434 0a la 2ab 4ab Sab 10bc 15c 30d 523 0a 2ab 4ab 6ab 7ab 9b 150 17c 603 0a 4a 12ab 13ab 20bc 27bc 30bc 37c 688 0a 3ab 6a’ 8bc 9bc 140 13c 24d 782 0a 3a 7a 12ab l9bc 20bc 23bc 25c 865 0a 2a 3a 7a 10b 12b 15b 18b 967 0a 7ab 12ab 22bc 25bcd 27bcd 390d 43d 1094 0a 17ab 25abc 48bcd 60cd 77d 117e 1399 1305 0a 20b 18b 24b 49c 63d 1039 104e The row means followed by the same 1etter(s) are not significantly (P - 0.05) different according to the Student Newman Keuls multiple range test. DD 10 C - accumulated degree days at base 10 C 275) Table A4-3: Influence of initial population densities Of P. enetrans on total (root + soil) population gynamics of P. penetrans associated with navy beans. INITIAL POPULATION DENSITY/100 cm3 SOIL 0 5 10 20 40 80 160 320 DD10C Final Population Density/100 cm3 soil + 9 root 254 0 4 8 10 41 71 122 199 341 0 5 10 14 27 49 98 118 434 0 4 15 23 28 63 109 162 523 0 7 23 35 51 122 164 186 603 0 12 31 32 40 110 145 160 688 0 21 36 42 46 151 206 239 782 0 ll 22 61 74 180 315 334 865 0 19 41 65 90 129 347 351 967 0 16 41 67 90 181 247 261 1094 0 16 39 68 105 204 285 322 1305 0 22 26 36 77 177 218 247 Row means followed by the same 1etter(s) are not significantly (P = 0.05) different according to the Student Newmans Keuls multiple range test. DD 10 C = accumulated degree days at base 10 C. Table A-5: Effect of different initial densities of P. penetrans on weight of navy bean roots over the growth period. INITIAL POPULATION DENSITY P. PENETRANS/lOO cm3 SOIL 0 S 10 20 40 80 160 320 DD1oc Root Weight (g/plant) 254 1.03a 1.02a 0.99a 1.48b 0.99a 0.95a 0.87a 0.73a 341 1.73b 1.64ab 1.63ab 1.50ab 1.19ab 0.85ab 0.45ab 0.78a 434 2.56c 2.98cd 3.40d 2.94cd 1.97b 1.42a 1.21a 0.97a 523 3.67b 3.66b 4.06b 3.18b 2.46a 2.19a 1.88a 1.48a 603 3.98c 3.79c 3.78c 3.50c 2.83b 2.48ab 2.36ab 1.77a 688 4.35d 3.93cd 3.84bcd 3.67abcd 3.21abc 2.9lab 2.75a1 2.85a 782 4.21b 4.13b 3.86ab 3.76ab 3.28ab 3.07a 2.84a 2.92a 865 3.87d 3.48cd 3.29cd 3.10c 2.51b 2.26b 1.93ab 1.40a 967 2.4lb 2.24b 2.01b 1.98b 1.50a 1.51a 1.18a 1.13a 1094 1.56b 1.50b 1.41b 1.26b 0.97ab 0.82a 0.75a 0.56a "Row means followed by the same 1etter(s) 0.05) different according to the student Newman Keuls multiple range test. are not significantly (P = Table A6: 280 Effect of different initial densities of P. penetrans on leaf area of navy beans over the growth period. INITIAL POPULATION DENSITY/100 cm3 SOIL 5 10 20 40 80 160 320 2 DD10C Leaf Area/cm 254 39.06c 45.166 43.66b 33.97b 25.296 23.77a 20.766 17.636 341 70.93c 72.48C 71.88c 69.96c 50.88b 40.72ab 40.66ab 31.896 434 123.26e 122.14e 117.70de 112.506 76.496 63.726 60.436 48.476 523 196.83a 195.278 188.01c 181.286 153.03c 118.87b 97.17c 83.926 603 308.99f 307.40f 306.30f 270.86e 238.32d 203.406 162.966 124.576 688 431.689 408.85fg 400.67f 369.15e 296.616 246.52C 212.796 138.94a 782 308.76f 307.85f 303.25f 223.70e 190.24d 129.50C 112.226 82.48a 865 189.626 179.526 176.246 112.61C 107.56c 71.796 50.21ab 35.20a 967 104.22C 103.146 100.746 75.636 72.086 39.13a 31.426 24.086 1094 53.796 51.116 49.236 34.34c 25.226 19.04ab 13.126 9.736 Row means followed by the same 1etter(s) are not significantly (P = 0.05) different according to the student Newman Keuls multiple range test. Table A7: Effect of different initial densities of P. penetrans on shoot fresh weight of navy beans over the growth period. INITIAL POPULATION DENSITY/100 cm3 SOIL 0 5 10 20 40 80 160 320 DD10C Fresh Weight/g 254 1.84b 1.77b 1.7Zab 1.566b 1.Slab 1.49ab 1.316b 1.21a 341 2.27bc 2.48c 2.86d 2.23bc 2.04bc 1.89ab 1.766 1.516 434 3.83c 4.12c 4.26c 3.19b 2.94ab 2.53ab 2.266 2.166 523 6.53c 6.94c 7.27c 6.09c 4.93b 4.34ab 3.236 3.086 603 9.82d 11.42e 12.39e 9.376 7.63c 6.24b 5.26ab 4.196 688 14.89d 16.10d 15.97d 11.79c 9.03b 7.93b 6.73b 4.426 782 12.39c 14.47c 13.38c 8.50b 8.30b 5.946 5.126 3.866 865 7.77c 9.1Sd 8.98d 5.93b 5.44b 4.086 3.386 2.936 967 5.39cd 5.756 6.22d 4.50c 3.58b 3.01ab 2.426 2.08a 1094 3.16c 4.53c 4.65c 3.10b 2.26ab 2.03a 1.506 1.34a Row means followed by the same 1etter(s) are not significantly (P = different according to the Student Newman Keuls multiple range test. DD 10 C = accumulated degree days at base 10 C 0.05) 281 Table A8: Effect of different initial densities of P. penetrans on dry weight of navy bean shoot system over the growth period. INITIAL POPULATION DENSITY/100 cm SOIL 0 5 10 20 40 80 160 320 DD10C Dry Weight/g 254 0.77d 0.73cd 0.68de 0.66de 0.656bc 0.606b 0.54ab 0.506 341 1.20c 1.18c 1.08c 1.03c 0.85b 0.786b 0.69ab 0.596 434 1.96b 1.65b 1.58b 1.44b 1.006 1.926 0.826 0.746 523 2.47c 2.39c 2.28c 2.18c 1.73b 1.106 1.016 0.896 603 4.23e 4.17e 4.07e 3.60d 2.49c 2.07b 1.316 1.056 688 5.64d 5.52d 5.51d 4.77c 3.72b 3.44b 2.496 1.666 782 4.04c 4.02c 3.99c 3.20b 2.81b 2.166 1.486 0.906 865 2.55d 2.48d 2.19d 1.39c 1.26b 0.89ab 0.726b 0.546 967 1.41c 1.31c 1.29c 0.89b 0.80ab 0.686b 0.466b 0.366 1094 0.99d 0.91d 0.90d 0.60c 0.46bc 0.356bc 0.256b 0.126 Row means followed by the same 1etter(s) are not significantly (P = different according to the student Newman Keuls multiple range test. DD 10 C = accumulated degree days at base 10 C. 0.05) 1282 Table A9: Interactions of initial density of P. penetrans and temperature on final root densities o P. penetrans. Temperature (C) Initial density P. enetrans/ 15 20 25 30 100 cm3 8011 Final Population Density (P. penetrans/g root) 0 06 06 06 06 25 5b 7b 12c 5b 150 20d 35b 62f 20d 300 27de 79f 92f 29de Column means followed by the same 1etter(s) are not significantly (P = 0.05) different according to the Student Newman Keuls multiple range test. Table A10: Interactions of initial density of P. penetrans and temperature on final soil population densities of P. penetrans Temperature (C) Initial density P. penetrans/ gig 20 25 30 3 100 cm soil Final Population Density (P. penetrans/100 cm soil 0 0 0 0 0 25 20b 37c 590d 24b 150 40c 94ef 128fg 45cd 300 72de 1629 237i 70de Column means followed by the same 1etter(s) are not significantly (P = 0.05) different according to the Student Newman Keuls multiple range test. 2£33 Table All: Interactions of initial density of P. penetrans and temperatures on final total population densities of P. penetrans. Temperature (C) Initial density P. penetranS/ 15 20 3 25 30 100 cm 3011 P. penetrans/100 cm + 9 root 0 06 06 06 06 25 25b 44c 70d 29b 150 60d 129fg 157g 67de 300 99ef 240h 329h 9968f Column means followed by the same 1etter(s) are not significantly (P - 0.05) different according to the Student Newman Keuls multiple range test. Table A12: Effect of P. penetrans on height of navy bean plants at different temperatures. Temperature (C) P. penetrans/ 15 20 25 30 100 cm 5011 Plant Height(cm) 0 12.7c 18.7f 21.89 24.7h 25 12.2c 17.1ef 21.19 23.29h 150 9.4b 13.60d 15.3de 18.4f 300 7.26 11.3bC 12.5C 15.6de Column means followed by the same 1etter(s) are not significantly (P = 0.05) different according to the Student Newman Keuls multiple range test. 284: Table A13: Effect of P. penetrans on weight of navy bean roots at different temperatures Temperature (C) P. penetrans/ 15 20 25 30 100 cm 5011 Root Weight (g) 0 0.61ab 1.16c 2.09d 0.88bc 25 0.580d 1.08c 1.92d 0.82bc 150 0.256 0.526b 0.64ab 0.526b 300 0.206 0.336 0.516b 0.286 Column means followed by the same 1etter(s) are not significantly (P = 0.05) different according to the Student Newman Keuls multiple range test. Table A14: Effect of P. penetrans on dry weight of navy bean shoot system.at four different temperatures. Temperature (C) P. penetrans/ 15 20 25 30 100 cm 5011 Shoot Dry Weight (g/plant) 0 0.4706 0.83f 1.519 0.60de 25 0.28ab 0.48Cd 0.77ef 0.396 150 0.213 0.36b 0.63de 0.286b 300 0.11a 0.28ab 0.44Cd 0.12a Column means followed by the same 1etter(s) are not significantly (P = 0.05) different according to the Student Newman Keuls multiple range test. 28E5 Table A15: Effect of P. penetrans on yield of navy beans at different temperatures. 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Interactions of soil type and soil moisture on final root densities of g, penetrans associated with navy bean Matrix potential ( - Centibars) Soil Type 1000 500 100 50 10 5 Final population density (P. penetrans/g root Sandy loam 6 10 23 88 27 7 Sandy clay loam 5 17 38 66 20 28 Clay loam 2 4 10 37 28 8 LSD (5 %) = 19 Table A26-4. Interactions of soil type and initial density of E. penetrans 3 Initial population density Pi/100cm soil 0 150 SOll type Final population density (P.4penetrans/Q root) Sandy loam 0 53 Sandy clay loam 0 58 Clay loam 0 29 LSD (5 %) = 11 Table A26-5. Interactions of soil moisture and initial density of g; penetrans Matrix 3 potential Initial population density of (P./100cm soil) {-Centibars) Q 150 l 3 44 Final population density (P. penetrans/100cm soil 1000 ’ 0 9 500 O 20 100 0 46 50 0 127 10 0 50 5 O 28 LSD (5 %) = 16 mmhu Hflom u U l Acausmuom xfluums aflom u m mcmnumcmm .m mo wuflmsmp :oHumHsmom HMHMHGH u ¢ Hmvam.mon homom.momom mm mommm mmmma.o mmmmv.a mammm.mmoa mvamm.mmmoa oH om< mmme.o mmmmv.a mammm.mmoa mwamm.mmmoa 0H om Hammo.o Hmoom.m mmmbo.hmna mmamm.mamm m um ««« oocoo.o Hmmmo.mH mmmoo.vomaa ommvo.o~mwm m m< Hammo.o Hmoom.m mmmwo.hmha mmamm.mamm m U ««« ooooo.o Hammo.mH mmmoo.¢omaa omowo.ommmm m m «a; ooooo.o wowm>.vma wonmb.mvbmoa wohm>.mvhmoa H d momHN.mmooom 50H Hm>mH .mHm m m: mm as Hmuoe 1. condom 9 mocoflno> mo mflmwamcd "Nibmd canoe 2 HHom mEoooa\m:muumcmm .m Hafiuflsfl u m HHm u mmv omH mm mm mm mm vm ma oma O O O O O O O smoq mmHo hm hm me mm mm 0H omH Smog O O O O O O O amHo scamm om ooa mom mv Om OH omH O O O O O O O anon macaw O OH om OOH OOm OOOH Hm Hmumnflucmo IV Hmwucmuom xfluumz Hwom Eoooa\mmmuumcmm .m m momma >>mc nuw3 pmumfiUOMmm manhumsmm monocwamumum wo mmwufimcmp cofluwasmom HHOm Hmch co mcmuumcwm .m can whopmHoE HHom mo uommmm “Hunmmmanms 294 Table A27-3. Interactions of soil type and initial density of P. penetrans on final soil densities of P. penetrans associated with navy bean Initial density~(P. penetrans/100cm3'soil Soil Type '0 150 1 Final population density (P. penetrans/100cm” soil Sandy loam 0 71 Sandy clay loam 0 72 Clay loam 0 48 TableA27-4. Interactions of soil type and soil moisture Matrix potential (-centibars) Soil Type 1000 500 #100 50 10 6 Final population density (P. penetrans/100cm3 soil Sandy loam 7 19 23 101 50 15 Sandy clay loam 5 13 33 84 43 39 Clay loam 6 12 31 43 36 14 LSD (5 %) = TableA27-S. Interactions of soil moisture and intital density of P. penetrans Initial population density (Pi/100cm3 soil) 0 150 Final population density (P. penetrans/100cm Matrix Potential ( - centribars) 3 soil 1000 0 11 500 O 28 100 0 58 50 O 152 10 0 87 5 0 45 295 HHomtmsoOOH\»uHmcmO mamuumcmm .m HmHuHcH n 4m MO ONH OOH HO HO OH OmH O O O O O O O smog mmHo OOH FNH OON NOH Om ON OmH smog O O O O O O O OMHo mocmm we OOH ham OO hm Om OmH O O O O O O O smog mccmm m OH Om OOOH oom OOOH um Amumnfluucmo IV Hmwpsmuom xfluumz Hwom EcooH\mcmuumcwm .M m .mcomn w>ms nufl3 pmumaoommm msmuumcmm .m mo mmfluwmcmv HHMOm + poonv Hmuou Hmcflm so musumwoa HMOm mo uommmm "mmfi magma 296 muwmcmp msmnuocmm um HoHuHGH mam» HHom u U HMHusmuom xHHumE u m u a wmwmm.m OOOO0.00H NO mommm NmHmm.O mmmmo.H vmmmh.~ bmmmm.nm OH omd «« ONOO0.0 «HOOO.N vmmm0.0 nmmmm.mw OH om ~OOMH.O Hmmvo.m mmovm.m OMHO¢.OH m Ud «as HOOO0.0 OOOON.O mmOO0.0H mmmom.mm m m< «ga OOOO0.0 Hmvmm.>m vmmbO.nm OOOmH.¢mH m o ««« OOOO0.0 mmmhv.mm Hmmmq.O>H woemv.mmm m m «a« OOOO0.0 mmmvh.mm Ohmmv.mmm Ohmmv.mmm H 4 ~mwvm.mmOH OOH Hm>mH .mHm m m: mm mm Hmuoe mousom wocoHum> mo mHthOC¢ umIm~¢ mHnme HHom mEoOOH\>uHmcw© mcmuumcmm .m HMHu . n HR O.H H mm QmHv H.O m.OH O.NH m.MH «.mH O.mH omH H.HH O.HH 0.0H h.vH O.mH O.mH O N.m ~.OH 0.0H m.mH v.vH ~.OH OmH m.~H H.mH O.HN m.OH m.OH 0.0H O amHo ~.m O.HH 0.0H 0.0H 0.0H m.OH omH EMOH meU aocmm O.mH O.mH O.mm 0.0H, O0.0H H.OH O smoq accmm AEov zumqu boom H m OH om OOH oom OOOH .m HmHmnHusmo uv HMHucmuom xHuuoz ucmumMMHp me um czoum muoou coon >>mc mo cumcmH so mcmuumcwm .m mo “comma mHMHucwuoglumum3 HHom “Hlmmd mHQMB 297 Table A29-3. Interactions of soil moisture and.initia1. density of P. penetrans on length of navy bean roots. ' Initial population density (P. penetrans/100cm3 soil Matrix potential ' O 150' (- Centibars) Root Length (cm) 1000 16.8 15.4 500 15.4 14.1 100 17.3 15.6 50 21.3 14.9 10 12.9 10.9 5 12.1 7.8 LSD (5 %) = 1.0 Table A29-4. Interactions of soil type and Soil moisture Matrix potential ( -centibars) Soil Type 1000 500 1000 50 10 5 Root Length (cm) Sandy loam 17.7 15.3 18.2 20.9 12.8 10.6 Sandy clay loam 16.3 15.5 17.2 19.2 11.7 10.3 Clay loam 14.3 13.5 14.1 14.4 11.1 9.2 LSD (5 %) = 1.4 mama HHOm u U HMHucmuom xHHumE u m huHmswU mcmuumcmm “M HMHuHCH I d 298 NOOH0.0 ONOO~.H NO mommm OOOO0.0 NOOO0.0 NOOH0.0 ONOOH.O OH om< «O OONO0.0 «OOOH.O OOOO0.0 OOOO0.0 OH om OOOO0.0 ONOOO.~ OHOO0.0 ONOO0.0 m om *«« OOOO0.0 NHOO0.0 NOOOH.O OOOO0.0 O m< ««« OOOO0.0 OOOO0.00 OOOO0.0 ONHHN.H m o «.x OOOO0.0 OOHO0.00 OOHO0.0 NOOO0.0 O m ««« OOOO0.0 OOOO0.00 OOOH~.H OOOHN.H H < OOOOH.O OOH Hm>wH .OHO m m: mm mo Hmuoa MDHDDM mocmHHmp mo mHmemsm "Niomd mHQMB HHOm mEoOOH\mcmuumcmm .m mo %UHmcm© :oHumHsmom HMHDHGH n Hm OH.O AOO OOHO OH.O OH.O O0.0 ON.O OH.O OH.O OOH OH.O OH.O O0.0 O0.0 OH.O -.O O OOHo O~.O O0.0 O0.0 O0.0 ON.O ON.O OOH smog H0.0 O0.0 ON.H OO.O NO.O O0.0 O OmHo Oncmm -.O O0.0 O0.0 N0.0 O~.O ON.O OOH O0.0 H0.0 HH.H NO.O OO.O O0.0 O smoH Owcmm Amc uanmz OOO noonm O OH OO OOH OOO OOOH Hm AmumnHucmo Iv HmHucmuom XHHumz mHmHusmuom Hmum3 HHOm usmHmMMHp me um c3oum mucmHm coma >>ms mo uanm3 mup co mcmuumcmm .m mo pommmm uHlomd anme 299 TableA30-3. Interactions of soil type and soil moisture on shoot dry weight of navy beans Matrix potential (~centibars) Soil Type 1000 500 100 50 10 *5 Shoot dry weight (g) Sandy loam 0.30 0.31 0.57 0.82 0.56 0.30 Sandy clay loam 0.32 0.30 0.62 0.97 0.67 0.34 Clay loam 0.20 0.17 0.53 0.52 0.17 0.16 LSD (5 %) = 0.10 TableA30~4. Interactions of soil moisture and initial density of P. penetrans . . . . 3 . Matrix potential Initial population den31ty (Piloo/cm soil) '(- Centibars) 0 150 Shoot dry weight (9) 1000 0.31 0.23 500 0.28 0.24 100 0.78 0.36 50 1.0 0.53 10 0.6 0.38 5 0.3 0.22 LSD (5 %) = TableA30-5. Interactions of soil type and initial density of P. penetrans Initial population density (Piloo/cm3 soil) 0 150 Shoot dry weight—(9) Sandy loam 0.60 0.35 Sandy clay loam 0.66 0.41 Clay loam 0.35 0.22 LSD (5 %) = .06 300 mam» HHom u o HmHucmuom xHuums u m muHmcmO mmmuumamm hm HmHuHcH u m OOOO~.H OOOO0.00 NO mommm 8.8 ~OOO0.0 OOOO0.0 OONHH.O OOONH.HO OH omm «8. ONOO0.0 OOHO0.0 OOOO0.0 OOOO0.00 OH om «88 HOOO0.0 OOOO~.OH OOON0.0H OHOO0.00 m om «a. HOOO0.0 OOOON.O HOOO0.0 OOOO0.00 O m4 ««8 OOOO0.0 OHOOO.HOH OOOO0.00H OOOO0.000 m o «*8 OOOO0.0 OOOH0.0~H HHOON.OOH OOOOO.HOO O m ««« OOOO0.0 OOON0.00~ OOOOO.HON OOOOO.HON H m OOOO0.0~OH OOH Hm>mH .mHm m m: mm mm Hmuoe mousom mocmHum> mo mHWNHmc¢ "NIHmd anme llllllll I H HHom mEOOOH\mcmuust .m mo wuHmsmp HMHUHGH u .m O.H u HOO OOHO 0.0 «.mH 0.0H O.~H ~.O H.O OOH O.HH O.~H 0.0H 0.0H O.O 0.0 O OOHo O.HH O.~H 0.0H 0.0H O.HH 0.0H OOH smog 0.0H ~.OH O.O~ 0.0H 0.0H O.~H O mmHo macaw H.OH 0.0H 0.0H 0.0H O.~H O.HH OOH «.mH 0.0H O.mm 0.0H. ~.OH 0.0H O smog Occmm Eo M.mHmm paw m H O OH OO 1H, O OmH. H OOO OOOH .m HmnmnHucmo iv HMHucmuom xHuumz .mHm>mH musumHOE uanGMMHU me um c3oum mucmHm coon >>mc mo uanm: so mcmuumcwm .m mo uommmm "HIHm4 GHQMB 301 TableA31-3. Interactions of initial density and soil moisture on height of navy bean plants Initial density ' "Matrix potential (-centibars) ggigenetranS/loocm 1000 500 100 4 50 '10 5 Plant Height cm/g root 0 11.9 12.3 18.2 20.7 16.8 12.7 150 9.8 10.4 14.1 15.5 13.3 10.9 LSD (5 %) = 0.8 TableA31-4. Interactions of soil type and initial density of P. penetrans 3 Initial population density (Pi/100cm .soil) Soil Type 0 150 PiantfihEight(chi Sandy loam 17.1 13.6 Sandy clay loam 17.2 12.9 Clay loam 12.0 10.4 LSD (5 %) = 0.5 TableA31-5. Interactions of soil moisture and soil type Matrix potential (-centibars) Soil Type 1000 500 100 50 10 5 Plant height (cm) Sandy loam 12.9 12.8 17.2 20.4 16.5 12.2 Sandy clay loam 11.8 13.3 17.2 19.6 15.5 12.8 Clay loam 7.8 7.9 14.0 14.2 13.0 10.3 LSD (5 %) = 1.0 0mm» HHow u o HaHucmuom xHHuaE u m Illa- I wuHmcmo wcmuumsmm .m.HaHuH:H u m 302 OOONO.O OOOOO.OO mommm ONNOO.O OONOO.O OOOOO.O OOOOO.O owc NHOOH.O ONONO.H OOHOO.O OOOHO.O ow ... NOOO0.0 OOONO.NH ~ONON.O aaOaO.OH om ... OOOO0.0 OOOON.OH ONOOO.O ONONO.ON ma ... OOOO0.0 OOOOO.OO OOOOO.O~ OOHOO.aO o ... OOOO0.0 OOOOO.HO OOONO.O~ OOOOH.O~H w ... OOOO0.0 OOaOm.HOm OOOOO.OaH OOOOO.OOH a HOOO~.OHa OH Hm>mH .mHm m m: mm mo Hauoe mouoom mUZMHHab mo mHmNHacd "NINm4 mHnma HHom mEoOOH\muHmcm© msmuumcmm .M HmHUHSH I Hm O0.0 u AOOO cwq mm.~ NO.O O0.0 OH.O Na.m aO.~ OOH ~0.0 O~.O ~O.O OO.a OO.O :OO.O O maHo OO.~ NO.O OO.O HO.O O0.0 OO.a OOH caom 1O.O aO.w OO.O OH.O OO.O OH.O O maHo macaw ma.m ~O.O mm.O -.O NO.a O0.0 OOH O0.0 O0.0 OO.OH OO.O am.O OO.O O caoH macaw ANEom moan uoom O OH OO O H OOO OOOH .m AmuanHucmu IV HmHucwuom umumz HHom WHMHUCMUOQ .Hmfimm UCOHOMMHU me um CBOHm wucmHQ mama >>ac wo amum uoou co wcauumcmm .m mo uomwmm "Himmd anwB 303 TableA32-3. Interactions of initial density of P. penetrans and soil moisture on area of navy bean roots Initial density Matrix potential‘(-centibars) P: penetrans/100cm 1000. . 500....100 50 .. 10 a 5 301 ‘root area (cmz) 0 4.7 5.1 6.0 9.0 7.7 5.4 150 3.6 3.7 4.3 5.4 4.1 2.9 LSD (5 %) = 0.4 Table A32-4. Interactions of soil type and initial density of P. penetrans Initial population density (Pi/100cm3 soil Soil Type 0* 150* root area (cm2) Sandy loam 7.4 4.5 Sandy clay loam 6.7 4.0 Clay loam 4.9 3.5 LSD (5 %) = 0.30 TableA32-5. Interactions of soil moisture and soil type Matrix potential (-Centibars) Soil Type 1000 500 100 50 10 ‘ 5 root area (cmz) Sandy loam 4.5 5.2 6.0 8.2 6.7 5.0 Sandy clay loam 4.8 4.5 4.9 7.5 6.0 4.4 Clay loam 3.2 3.5 4.6 5.9 4.9 3.1 LSD (5 %) = 0.52 304 mmmu HHom u U HaHucmuom xHHumE u m mcmnpmcwm am mo muHmch HHom HMHuHcH n_¢ OOHv0.0 mammm.m NO mommm Hvam.O mmamO.H OHva.O HOHmv.O OH 0mm ...MHOO0.0 ONNNN.O OOMOH.O mmva.H OH um ...OmOO0.0 mmOmm.m OONOM.O OOmN0.0 m um ...HOOO0.0 mmmwm.O mHamm.O OOONO.H m md ...OOOO0.0 ONOH0.00 mmOmm.m OHmmO.m m U ...OOOO0.0 Nmmvv.mm OOOMO.N mvomO.MH m m ...OOOO0.0 HNOOH.OOH HOOON.O HOOm~.O H 4 OOOOO.vm OOH ,Hm>mH .mHm m w: mm mo Hmuoe mousom mUCMHHM? mo mHmmHmafl "Nammfi anme mcmnumcwa .M HmHuHcH n Hm O~.O u AOO quv om.O O0.0 O0.0 N0.0 ~0.0 m¢.O omH mv.o mm.O O~.H Ov.H mm.O m0.0 O OaHU mm.O O0.0 OH.H OO.H O0.0 M0.0 OmH Smog ~0.0 am.O Om.~ HO.~ «O.H HO.H O >aHU >©cam m0.0 O0.0 Ov.H HO.H O0.0 O0.0 OmH O0.0 Oa.H «0.0 am.m OO.H ON.H O saom macaw O.O Awe aHaHm caam H m OH om OOH com OOOH m Amhmnwucmu IV HMHucmuom xHHumz . . O .mHmHuanoo xHHumE ucmumwpr me pa csouo mcamn Ono mo UHmHh co mcmnumcmm .m mo pomwmm "Himmfi GHQMB TableA33—3. Interactions of soil type and soil moisture on field of navy beans Matrix potential (~centibars) Soil Type 1000 ‘5005 5100 50 ’ 10“‘ 5 Dry bean yield (9) Sandy loam 0.96 1.20 1.83 2.06 1.11 0.78 Sandy clay loam 0.87 0.96 1.55 1.72 0.80 0.62 Clay loam 0.59 0.72 1.11 0.95 0.83 0.40 LSD (5 %) = 0.16 TableA33-4. Interactions of soil moisture and initial density of P. penetrans Matrix potential {-centibars) Initial den§lty 1000 500 100 so 10 3 (Pi/ 100 cm 8011) Dry bean yield‘Tg) 0 1.0 1.16 1.88 2.04 1.12 0.71 150 0.62 0.76 1.10 1.11 0.71 0.49 LSD (5 %) = 0.08 TableA33-5. Interactions of soil type and initial density of P.penetrans Initial population density (Pi/100cm3 soil Soil Type 0 150 Dry bean yield (9) Sandy loam 1.69 0.96 Sandy clay loam 1.33 0.84 Clay loam 0.93 0.60 LSD (5 %) = 0.16 I306 HHoa msoOOmeuHacaa a .m HaHchH .. m HH ON MH ON Awm own. «O NO NO NO OON Nv OO NNH v0 OO OOH NO OOO ON Om ON Nm OOH «N mH NN NH Om OO mm OOH O O O vN Nw NN N OH O m «H O mN O O O O O O O O O O O O O smog Oocmm O Om m ON NO ON NN cm on Om mo Oq OOm OH vN OH OH mm ON O NN OH OH on mH OOH H v n O ON OH N O m O O O ON O O O O O O O O O O O O O anq OaHo OH NO OH mv NHH Ov Om OO O OO mNH OO OOO O NN O NN OOH mN mH mm NH mN Om NN OOH H O H OH ON OH O O m O OH O mN O O O O O O O O O O O O O 5804 Opcam uoou O\mcauum:mm hm HO m on OOOH m Om OOOH m Om OOOH m 0M\‘ ooOH AmmanHucmo u. HaHucwuom mouas HHom vaH‘ Nada}, Ode‘ mON HOOHQQO mace omnmwc pwuaHseooo< .WEHu um>o mcauuocwm .M mo meuHmcmp coHuaHoaoa uoou co mcmuuwcmm .a mo mmHuHmcmc :oHuaHsmom HaHuHcH pca wax» HHOw HaHucmuom uwua3 HHOm mo wcoHuomumucH mo uoomwm "HlvmcoHnme 307 .HHOm mEo OOH \ wcauuoswm.nm.mo OuHmch HMHuflcw u U HMflucouom xfluumE n m mam» HOOm n m OOOOO.HNH OOOO0.0000 NO mommm ..OOOO0.0 OOmmv.N OOOmv.OON NmmHm.HOmm NH 0mm ...OOOO0.0 OOva.OH mOHHm.OmmH OmOOO.HOOO O om ...OOOO0.0 NOaNO.vH vONNv.HOOH OOOmm.OOOOH O U< ..OOOO0.0 OOOOO.m OOmm0.0mv HOOHO.HMOH a mm ...OOOO0.0 mNHmv.mvH «HOHN.mOOOH HaOmO.mOva m u ...OOOO0.0 vaOO.Hm OvaO.HOOm OONOv.mOOO N m ...OOOO0.0 OONOO.mH OOOON.OOOH OOOOm.OHOm N m OHmmv.HOOOO OOH Ha>am .OHw m w: ww mo Hauoe mousom mocmHum> mo mHmOHmcd 0 OH Do OOOH um mmauumcom .m mo mmHuHmcmp COHuHasmom Doom :0 mcauumcmm .O OO Oprcmp HaHucH Una ousumHOE HHom .mmwu HHom mo mcoHuomHmusH "vam< mHQaB 308 TableA34—3. Interactions of soil type and soil moisture on final root densities of P. penetrans associated with navy bean Matrix potential (-Centibars) Soil Type 1000 50 '5 Finalgpopulation density (P.¥penetrans[g‘root) Sandy clay loam .5 38 20 Clay loam 11 20 8 Sandy loam 20 39 24 LSD (5 %) = 6 Table A34-4. Interactions of soil type and initial 'density of P. penetrans Initial population density (Pi/100cm3 soil) Soil Type 0* 25 150 300 Final population density (P. penetranslg root) Sandy 1aom 0 6 27 50 Sandy clay loam 0 4 13 34 Clay loam 0 5 16 87 LSD (5 %( = 8 TableA34-5. Interactions of soil moisture and initial density of P. penetrans Matrix Initial population density (Pi/100cm3 soil) potential (-Centibars) 0 25 150 300 Final population density (P. penetrans/100cm3 soil) 1000 0 3 11 33 50 0 9 33 86 5 0 3 12 53 LSD(5 %) = 8 1309 .H .HHom OEUOOH you Ouncon wcauuwcmm .M HaHuwcH u .O O u HOO OOHO NO OON OO O vm OH NN NO OH ON OO OH OOO OO OOH OO O NN OH OH Ov OH OH NO OH OOH ON HO ON v ON NH O OO OH O O O ON O O O O O O O O O O O O O smog Ovcmm vv NNH ON O «H O O NH O OH «O O OOO NH Om OH O OH O O vH O O OH O OOH OH NN O N O N O ON HH O O O ON O O O O O O O O O O O O O smog OOHU OO O... OH O «H O O OO N OH HO OH OOO Om OO OH O NH O OH on O NH ON NH OOH O OO O O OH N O ON O O O O ON O O O O O O O O O O O O O 3804 OOHU Omcam Hwom mmoocmwwcauumcmm.m H O Om OOOH OO OOOH (O OO OOOH\ (O OO‘ OOOH .O quabHrucmer HaHucmuom umuaz HHom OVOH OOOH OONI HUOHQQO name mmumwc cmumHsfisoo¢ i .mEHu um>o mcauumcom .M no mmHuHmcwc coHuaHsmoa HHom :o mcauuocom .m no moHuHmcoc soHuaHsQom HaHuHsH ucmummch Oca mama HH0m.Hawu:muom umuaB HHOO mo :oHuomumuCH mo noomum OHIOO¢ mHnme 310 HHow Eo OOH \ wamuuocmm .M mo Oufiwcmv HaHuHcH n u m HaHucmmon xHuuaE u m OOOH HHow n < OOOMH.OM OOOO0.0¢ON NO mommm «.MOMH0.0 ONOmm.N NvovH.Om OHmm0.000H NH Omd «««.OOOO0.0 OOHN0.0H Ovam.OH¢ Hmva.OO¢N O 0m *««.ooooo.o mOHOm.m NOom0.0mm COMOOOONON O Dd *«a OOOO0.0 OOvH0.0 HmOm0.00m ONOO0.00¢H v md *«¢.ooooo.o NOOmm.Om OOOOO.MONN OONHN.OOOO m U ¥%«.ooooo.o OOvON.HO OOmmv.mOvm HVOO0.0000 N m *fcooooo.o HOOOO.H¢ Hmem.HOOH MOONO.MONm N fl OONHN.OOOON OOH HMUOB Ha>aq OHw m w: ww mo aoccow mocaHua> mo meOHac< . .UOHQQ OOOH um mcauuwcmm .M mo mmHuHmcmO HHom co mcauumcmm .m cam waxy HHom .musumHOE HHom mo mcoHuoaHmucH HNlmm.< mHQMB 311; .HHom OED OOH \mcauumcmm .m «o OuHmcmn HaHuHcH u U HMHucmuom xHuuaa u m mama HHom n < OOONO.HON OOOOO.HONON NO momma «a. OOOO0.0 OOOO0.0 NOOOm.vmvH OOOON.NHNOH NH Um< «c. OOOO0.0 OOOO0.0v NOOO0.00NNH OHOVH.OOOOO O Um ... OOOO0.0 OOva.OH OOOOH.OOvO HOvHO.mHJdOHm m m: mm mm Hauoe wou50m .mocaHua> wo mHmOHac< "NIOmd poaB ON u HOOV OOH OOH OHm NO OO OOH ON NO OOH Om OOO OO vNN HNH ON OO ON Om NO ON OOH Hm OO Om OH ON NH O «O O ON O O O O O O O O O O AHHoa OOH\8OO mancaa coHuchmom HacHO HHow O EUOOH mwcamw II Imama .m OuHmcwc O OO OOOH O OO. OOOH O OO. OOOH HaHuHcH OmuanwwchIOHaHucwuom umumz Hmom EaOH Opcmm EcOH xaHU EaOH xaHU Npcmm amme HHow mcauumcmm .M mo mmHuHmcmo coHumHsaom HOCHO co wcauumsmm mscocmHmuaum HO mQHUHmch coHustaom HauHucH oam max» HHow .wuoumHOE HHOO O0 uomwum "HIOmo unOHm3 uoou cawn >>ac co mmmmwmmmm .m mo mmHuHmcoO :oHumHsmom HaHuHcH ucmumOOHO can mam» HHow .HaHucmuom “mum: HHom O0 mcoHuoaumucH mo uomOOm “HIOOO mHnaB 314 mcmuumsmm .M mo Ouwmcmo HmwuHcH U Hafiucouom xHuuaE u m mama Hflom n O OHOOH.O ONOOO.NH NO mommm OmOO0.0 OONO0.0 OONNH.O OOOOO.H NH om< .OOOH0.0 OOONO.N OOOO0.0 OHNOO.N O om OOOO0.0 OOOON.O OONO0.0 OOOON.O O oO HNOO0.0 OOOO0.0 NOOOH.O ONOO0.0 O OO ...OOOO0.0 OOHON.HO HOOO0.0H OOHON.NO m o ...OOOO0.0 OOONN.OO OOOO0.0 OOOOO.HH N m ...OOOO0.0 OOOO0.0H ONOOO.H OONO0.0 N m NONO0.00 OOH Ha>aq .OOw m m: ww Oc Hauoe PPM—90m mocmHHm? mo meOHmsd "OIOO.€< mHnt OOOO0.0 OOOOH.O NO mommm ONOON.O HOOON.H OOOO0.0 OONO0.0 NH oma OOOO0.0 OOOO0.0 OOHO0.0 OOOOH.O, O om .OOON0.0 OOOOO.N OONHH.O NNOO0.0 O om ...OOOO0.0 OHOON.O HHOH0.0 OOOON.H O m< ...OOOO0.0 OOOH0.00 OOONO.H OOOO0.0 O o ..OOHO0.0 NOHON.O NOOH0.0 OOOO0.0 N m ...HOOO0.0 OONHH.OH OOOO0.0 OOOOH.H N 4 NONOO.NH OOH Ha>am .OHw O w: ww ma Hauoe TOHHHOm mocafluab mo mOmOHacm uNIOm d. mHQMB 315 msmupmcom .M mo OUHmsmO HaOuOcH o HaHucmuom xHHuaE n m mmmu HHOO n m OOOO0.0 OOOOO.N NO momma OONH0.0 OOOO0.0 OOOH0.0 OOHHN.O NH om< ONOH0.0 OONO0.0 ONHO0.0 OOOOH.O O om OOONH.O OOOHO.H OOHO0.0 OOOO0.0 O DO ... OOOO0.0 OHOON.O OOOOH.O OHOO0.0 O OO ... OOOO0.0 OONON.OO OOOON.N OOOO0.0 O 0 «O. HOOO0.0 OOOO0.0H HOHO0.0 OOOO0.0 N m .. NONO0.0 HOON0.0 OOONN.O OOOO0.0 N m OOHNO.NH OOH Ha>aq OOw m wz Ow mo Hauoe LI condom mOQMHHmb mo mHmOHac¢ "OIOO4 anaB OOOOH.O OOOON.NH NO mommm OOOOH.O HOOH0.0 OHNNN.O NH 0mm HOONH.O OOOOO.H OOOON.O OOOOO.H O om OHOH0.0 OOOOO.H OOOOH.O OOOOO.H O U< ..OOOO0.0 NOOO0.0 OOHO0.0 OOOOO.N O md ... OOOO0.0 OONO0.00 OHNO0.0 OOOO0.0H O U ....HOOO0.0 OOOO0.0 OOHOO.H OOOOO.N N m . OOOO0.0 OOOO0.0 OOOO0.0 OOOOH.H N « OOOOH.OO OOH Ha>aq OOw O w: ww ma Hauoa mousom mocaHHm> mo meOHmsm "VIOm.4 a GHQMB 316 TableAB7-6. Interactions of initial density and soil moisture on weight of navy been roots " Initial density Matrix potential (-centibars) of P. .3penetrang/ 1000 50 ' 5 100cm. soil .. . root weight (g) 0 1.2 1.2 1.1 25 1.1 1.2 0.9 150 0.8 0.7 0.5 300 0.6 0 7 0.5 LSD (5 %) = .12 TableA37-7. Interactions of soil type and initial density of g. penetrans 3 Initial population density (Pi/100cm soil) Soil Type 0 25 150 ’ 300 root weight (g) Sandy loam 1.0 1.1 0.7 0.6 Sandy clay loam 1.1 0.9 0.7 0.5 Clay loam 1.3 1.2 0.6 0.6 LSD (5 %) = 0.12 TableA37-8. Interactions of soil moisture and soil type r Matrix potential (- Centibars) .- S 11 T e 1500 50 S O yp root weight (9) Sandy loam 0.7 0.8 0.7 Sandy clay loam 1.0 0.9 0.7 Clay loam 0.7 0.7 0.8 LSD (5 %) = 317 H. HHom OEoOOH\mmmmmmmmm .m we maHacaa HaHuHcH n .O O0.0 NH.O O0.0 OO. .OO OOHO ON.O N0.0 OH.O ON.O Ov.O O0.0 N0.0 O0.0 O0.0 O0.0 H0.0 O0.0 OOO H0.0 O0.0 ON.O Ov.O O0.0 O0.0 O0.0 O0.0 O0.0 O0.0 O0.0 Hv.O OOH O0.0 O0.0 O0.0 O0.0 H0.0 O0.0 OO.H OO.H HO.H O0.0 O0.0 N0.0 ON N0.0 O0.0 O0.0 O0.0 O0.0 H0.0 NH.N HN.O OO.H O0.0 O0.0 Ov.O O Smog Occam ON.O H0.0 OH.O O0.0 N0.0 O0.0 O0.0 N0.0 «0.0 ON.O O0.0 O0.0 OOO H0.0 O0.0 ON.O O0.0 O0.0 H0.0 O0.0 NO.H O0.0 O0.0 Hv.O O0.0 OOH «0.0 O0.0 O0.0 Hv.O O0.0 O0.0 OO.H OO.H NH.H O0.0 O0.0 O0.0 ON O0.0 O0.0 O0.0 N0.0 O0.0 O0.0 HO.H NO.N HO.H O0.0 O0.0 O0.0 O EOOH OMHU HN.O ON.O OH.O H0.0 O0.0 O0.0 H0.0 OO.H O0.0 N0.0 O0.0 O0.0 OOO O0.0 O0.0 ON.O Ov.O N0.0 O0.0 O0.0 OO.H O0.0 O0.0 O0.0 Ov.O OOH Ov.O O0.0 O0.0 O0.0 O0.0 H0.0 OO.H HN.N ON.H O0.0 O0.0 O0.0 ON O0.0 N0.0 O0.0 O0.0 O0.0 O0.0 OO.H OO.N NO.H N0.0 O0.0 O0.0 . O 5804 maHU Occaw HucaHm\OO ucOHwa Nun HO O OO OOH .O)» OO OOH . O OO OOH O O OOH kuaamucmo vawmmucmuom swam: Hwom OOOH OOOH‘ OOOH OON .wEHu uw>o unOHoz OHO uoosm coma O>acOuo mcauumcmm .M mo mmHuHmsmp :oHumHsmom HaHuHcH ucmHmOOHp can oQOu HHom .HmHucmuoa umum3 HHOO mo mcoHuoaumucH O0 nomOOm UOH OOO mmmo omuOmO cmumHssdoo< "Himmfi mHnt 318 mcmuumcwm .M O0 maHmcaa HaHuHcO n o HaHucmuom xHuuaE n m mam» HHOO n 4 OOOOH.O OOOHO.NH .NO mommm OOOO0.0 OOHO0.0 HOOO0.0 OOON0.0 NH um4 ... ONOO0.0 OOOH0.0 OOOO0.0 HOOOH.O O om ONOON.O OOOOO.H OOOON.O NONNO.H O U4 OHOO0.0 ONHO0.0 OHOOH.O OOOO0.0 O m4 «t. OOOO0.0 OHOH0.00 OONO0.0 HOOO0.0N O U ... .HOOO0.0 OOOO0.0H NHNNO.N Ova0.0 N m OOHO0.0 OOON0.0 OOOOH.O OHOON.O N 4 OOOO0.00 OOH Ha>anlmew m w: ww mo Hauoe mousom mocmHua> mo mHmOHac4 "OIOO.4 mHnt OOOO0.0 HNNON.O NO» mommm OHOO0.0 OHON0.0 OOHO0.0 HOOH0.0 NH. om4 HOOON.O OHHOO.H OHOO0.0 NOOO0.0 O um OOOO0.0 HOOON.O OOOO0.0 NNOO0.0 O 04 ... HOOO0.0 HOON0.0 NHHN0.0 OOOO0.0 O m4 .... OOOO0.0 ONOO0.0H HOOO0.0 OONOH.O O U ... OOOO0.0 NOHO0.00 ONOON.O OOOO0.0 N m ... OOOO0.0 ONOO0.00 OOOON.O HONHv.O N 4 HHOOO.H OOH Ha>aq .OHw m w: ww ma Hauoa monsom wocaHHOP mo mHmmHms4 ”NaOO.4,mHQaB 319 msmuumcmm..m mo Oufimcmc HOHUHCH HaHucmuom anumE n O max“ HHOm u 4 OOOO0.0 OOON0.0 NO mommm OOOO0.0 OOOO0.0 OOOO0.0 NHNO0.0 NH Um4 OONO0.0 OOOON.O ONHO0.0 OOOO0.0 O om HHOON.O OOOON.H NOOO0.0 OOOO0.0 O 04 «O OOOO0.0 OOOO0.0 OHOH0.0 OOOO0.0 O m4 ... OOOO0.0 ONOO0.00 OOHON.O HNOO0.0 O U ... OOOO0.0 HOON0.00 HOOON.O OOOH0.0 N O «O. OOOO0.0 OOOO0.0H ONOO0.0 OOOO0.0 N 4 OOOOO.H OOH Hm>mg OHw m w: ww mo Hauoa mousom mocaHHa> mo mammHms4 "OIOO.@ MHQaB .\ OOOH0.0 OONN0.0 NO mommm OOOH0.0 HONN0.0 ONOO0.0 OOOO0.0 NH Um4 OOOON.O NOOON.H OOOH0.0 ONOO0.0 O om OOHO0.0 HOHO0.0 OOOO0.0 OHON0.0 O 04 ... OOOO0.0 OONO0.0 HOOO0.0 OOOO0.0 O m4 ... OOOO0.0 HOOO0.00 HOOO0.0 NOONO.H O U ... OOOO0.0 OOOON.OO HOOO0.0 OOOO0.0 N m . OOOH0.0 OOHNN.O OONO0.0 OOOO0.0 N 4 OOOO0.0 OOH Ha>aq OHw O w: ww mo Hauoe .mbhbbm mocaHuab mo mHmOHms4 "Olmm.4 mHQmB 320 TableA38-6. Interactions of soil moisture and P. penetrans on shoot dry weight of navy beans. Initial density 3 Matrix potential (-Oentibarsl E. penetrans/100cm 1000 50' "5 soil "Shoot dry wei§ht‘(g) 0 0.37 0.54 0.46 25 0.35 0.51 0.42 150 0.27 0.43 0.33 300 0.18 0.31 0.24 LSD (5 %) = 0.04 TableA38-7. Interactions of soil type and soil moisture ‘ , Matrix otential (-centibars) 5°11 type 1000 IR 50 *3 Shoot dry weight Sandy loam 0.28 0.42 0.38 Sandy clay loam 0.30 0.39 0.31 Clay loam 0.31 0.53 0.39 LSD (5 %) = 0.04 TableA38-8. Interactions of soil type and initial density of P. penetrans. Initial population density (Pi/100cm3 soil Soil Type 0 25 “150 300 Shoot dry weight (9) Sandy loam 0.46 0.42 0.34 0.23 Sandy clay loam 0.40 0.38 0.31 0.25 Clay loam 0.51 0.48 0.38 0.25 LSD (5 %) = 0.04 321. fIlIIlIII- HHom OEUOOH\uwQ mmmmmmmmm .M O0 muHmch HmHuHcH u HO H.N o.N O.H 0.0 me QmHO O.HH H.OH 0.0H 0.0 N.OH 0.0 m.O m.NH 0.0 O.m N.m .m.m com O.NH 0.0H 0.0H O.HH 0.0H 0.0H 0.0 0.0H 0.0 0.0 0.0 m.m omH 0.0H 0.0N 0.0H 0.0H N.HN 0.0H m.HH 0.0H 0.0 0.0 0.0H 0.0 ON 0.0H H.Nm H.OH 0.0H N.Nm 0.0H N.mH N.HN m.HH 0.0 O.NH 0.0 o anq mocmm N.OH N.mH 0.0 0.0 O.NH 0.0 H.O N.O 0.0 0.0 0.0 H.m OOO 0.0H m.OH H.OH 0.0H m.mH H.OH 0.0 O.HH N.O m.m M.O 0.0 OOH H.MH 0.0H m.NH N.MH 0.0H M.NH 0.0 O.NH 0.0 m.m 0.0 m.m ON m.mH N.mN O.NH H.OH m.MN m.NH 0.0 H.OH 0.0 m.O 0.0 m.m o Eocn OMHU O.HH 0.0H N.O 0.0H 0.0H 0.0 0.0 N.HH 0.0 O.m 0.0 O.N com O.HH H.OH 0.0 O.HH 0.0H 0.0 0.0 O.NH 0.0 H.O 0.0 0.0 OOH 0.0H 0.0H 0.0H 0.0H 0.0H O.MH H.OH 0.0H m.O 0.0 0.0 m.O mN 0.0H 0.0N N.OH 0.0H 0.0N m.NH O.HH 0.0H 0.0 H.O N.m N.O o EOQH OOHU Opcam AEUO uAOHm: acmHm HO m cm OOOH m. cm OOH m on OOH m cm. OOOH OMuanHucmuer Hmmucmuom\uwua3 HHom OOOH OOOH OOOH mmN HUOHQO. mxmo omumon cmumHsesoo4 .meHu um>o :awb >>ac wo uanmc co mwmwmmmmm .M O0 mmHuHmch coHuaHsmom HaHuHcH ucmumOOHp nca max» HHOO .HmHucwuoa Houa3 HHOw O0 mcoHuoauwucH Oo uomuwm "HIOO4 mHnme mamuuwcmm «M mo huHmcmc HmHuHcH u o HMHucwuom xHHumE u m mam» HHom n O 322 ~oamm.~ mmmhm.oma mm mommm ~om~m.o mmam¢.o ~com~.a maooo.ma NH 0mm **« mmooo.o mmamv.¢ mwaom.aa onmom.om e on «m mmmoo.o momem.m mmm-.m oomvm.mv m um Hmmae.o ommmm.o moamm.~ m~¢m¢.oa v mm «m« oocoo.o mvvma.mq mmmmo.mfla mmmmm.mmm m u mmm ooooo.o ommmm.¢ma mommh.mme omamw.amm m m ««m ooooo.o mmmmm.om moooa.~m maoom.vma m m nmmaa.amma mom Hm>mq .mmm m m: mm mo Hmuoe wOHSOm mOCMHHmp mo mHmmHmad "mumm.< mHnma mmmom.o hmmmm.mm mm mommm mammv.o mommm.o Hmmom.o mmmmo.m NH 0mm m*« moooo.o mamma.m momHH.m mmomm.ma e um «mm ooooo.o nmqom.ma mvmmm.m ommmm.hm e um ««* oocoo.o mmmom.aa mmamm.m nomma.m~ v mm mm« ooooo.o mmmnm.mm mmvmo.m¢ mmmmm.vva m u *«m ooooo.o mmmvv.mva mmmmo.~n momma.eva N m ;*« ooooo.o oqmmo.mma mmoom.am moflmn.mma m m mommm.mmm boa Hm>mm .mmm m mm mm mm Hmuoe wUHSOm wOCMHHmb mo mHmmHmc¢ "mumm.4 mHnma 323 mamuumcmm .M mo huHmcmo HMHuHcH n u HMHpawuom XflHHME " m 0mm» HHom u 4 , mehv.m hOOem.mvm N5 mommm hNO¢0.0 OHOmv.O ONmm¢.H hOOHm.bH NH 0m< «mm OOOO0.0 MNOmN.NH mhvmv.N¢ Obmom.vON O um ONOvH.O VO>MO.H mOva.O OHOOH.vm O Dd VOOMH.O hmmmh.H HOMVN.O VOme.vN w mfi mmt OOOO0.0 OHOH¢.OO HOOOh.vmm Q>ONH.vOOH m 0 «mm OOOO0.0 «MOO0.00H hOhHN.th whmm¢.OOHH N m «mm OOOO0.0 NNmmv.ON hMOOm.Om fihONh.OhH N 4 OOHmH.HNmN hOH Hm>mq mam m m: mm mm Hmuoe mounom mocwHHm> mo mHm>Hmc¢ um.mm.m-mHQma HHHOO.m OOOO0.0HN Nh mommm OMNHh.O OOOMN.O OmmuN.N thNm.ON NH omd mmm OOOO0.0 hOmOO.m NOON0.0N OHMOO.th O 0m «mm OOOO0.0 NOONO.¢ OVHHH.¢H OhOOO.¢m O 04 HOOO0.0 thNv.N NNnO¢.h OOON0.0N v md «mm OOOO0.0 OmHOO.mNH hmva.Omm HOOON.OOHH m 0 mm« OOOO0.0 mmNOv.mHN HOOON.HOO Nthm.NOmH N m mmm OOOO0.0 mOmOH.VN vaOO.m> OOMNH.th N d hHmov.OhHm hOH Hm>mQ{wmm m m: mm mm Hayes mousom mOCMHHm> mo mHthmcfi "vumm.¢ymHnma mmmmmmmmm .M mo auHmcmv HmHuHcH u U HmHucmuom xHuqu n m mama HHOm u < mvmmo.c MHth.v Nb mommm OhmMH.o mNmNm.H mmomo.c aMOmc.H NH om< mum moooo.c mmHmN.O hmHhm.o mmmNN.N O um «um Nocoo.c anhv.O naemm.o Hmmom.N O om «c¢ Hmooc.c cvme.m mmOmm.o mmvvm.H v m< «mu coooo.c ommho.OmH mhth.a thNm.hN m U amm ooooo.o mmmOm.mm hmmmm.m «monm.HH N m «cc oocoo.o thNm.v> hNth.v vmemm.m N t hmHmb.mm FOH M 323 .mmm m m: mm me 132. no mouaow mocmHuw> mo mHmmHmcd "Ntov4 anme «N.o u Ammv nmq mm.o Om.o mN.o 5H.o mm.o OH.O hm.c vO.o HN.O com mm.o mm.H OO.o Om.o mO.o mN.o mm.c mm.o mm.o omH NH.H bO.N mo.H 0O.o vm.H Nm.o OO.H o.N OH.H mm MH.N vm.~ VH.H mm.o mO.H mm.o om.H ON.N hm.H o HucmHm‘\mO UHwHN camp N>mz m on 83 m cm. 83 m cm 83 mm HmumnHuCOUIHHmHucwuom uwumz HHoM. Emoq xvcmm Smog NmHU EmoH mmHU .mvcmm mm>s HHom mammn >>mc mo chHh co mcmuumcom manocmHNumum mo NuHmcmO :oHumHsmoq HmHuHcH vcm musumHOE HHOm .wmmu HHom mo uowuwm "Hooqd mHnma 325 Table A40'3- Effect of interactions of soil type and B. penetrans on yield of navy beans. Initial population density (Pi/100cm3 soil) Soil Type 0 25 I50 4300 Yield‘(g) Sandy clay loam 1.92 1.62 0.63 0.41 Clay loam 1.03 0.82 0.42 0.24 Sandy loam 2.04 1.62 0.98 0.55 LSD (S %) = 0.16 Table A40-4. Interactions of soil moisture and initial population density of g. penetrans. Initial population density (Pi/100cm3 soil Matrix_ potential (~Cent1bars) 0 25 150 300 Yield (9) 1000 1.09 0.92 0.44 0.21 -50 2.25 2.0 0.98 0.63 5 1.64 1.13 0.61 0.35 LSD (5 %) = 0.16 Table A40-5. Interactions of soil type and soil moisture "1 Matrix potential {-Centibars) Soil Type 1000 50 -5 Yield (g) Sandy clay loam 0.83 1.46 1.34 Clay loam 0.38 0.99 0.50 Sandy loam 0.78 1.94 1.17 LSD (5 %) = 0.14 326 .ummu mmcmm mHmHuHsz mHsmx mcmezmz ucmosum on» cu OGHOMOOOM HmO.O u mO ucmuwmeO mHucmonHcmHm uoc mum HmvumuumH mEmm may ma Om3oHHow memos CESHOU 0mm.m OO0.0N nmm.vmv OOO.v OO0.0N OOOH 0mm.m OON.mN QmO.va omm.m OO0.0H com onmm.N onmv.mN nvm.mov QmO.m 0mm.>H OOH anO.N namm.ON mOm.ONm nmvv.m nO.mH om nomv.m anN.ON mHOOHM bovN.m nNh.vH OH mON.N mOO.OH amm.va mOO.N mnH.NH O vaHmuMMMM\MuQ uanmmo.um wwmwmmmww meHmmm .uwcmwmmw HHom\nEo OOw\mmHomm mwumHsoHommm um .mcmmn >>mc mo OHme cam :uBOHm co msumHsoHommm moEoHo mo meuHmcmO ucmummmHO mo uommmm .HfimmHnt 327, .ummu mmcmm mHmHuHDS mstm mcmezmz pawnsum may on OGHOHOUOM AmO.O u my ucwnmmOHO mHucmoHOHcmHm no: mum HmvumuumH menu can an nm3oHH0m memos CESHOU UNHO OMO OmO.>m OON.> nhm.mm OOOH OOOm Omm UmN.Nm QOH.O nhm.Om OOO nmvH OUHm AN0.0N nomH.m nON.vm OOH MOO onHN mHO.HN mNh.v mOO.HN om Mam QMHH mOh.OH mHh.v MHO.ON OH mo mO mOH.OH mo.v mOH.H O HHom mEo OOH OBJQOchH ucmHm\Eo ucmHme ucme\NEo HHom mEo OOH \mwuomm mo .02 uoou w numcmH uoom uanm3 uoom mmum uoom \mmuomm mm mDEoHo .msuHsoHommO .m O0 monomm Mo Monaco mam :oHuomOcH boom HmNHnnuoomm :0 can muoou coma >>mc uo numcwH Ocm uLOsz .mmum co mobmeoHOmmO .O OO mmHuHmch ucmnmmmHO mo Mommmm .Nv< mHnme 328 ‘i .ummu MOCMm mHmHuHsz mstm :Mezmz ucmcsum on» on OGHUHOOUM AmO.O u my ucmummeO OHHCMUHOHCOHm uoc mHM HmvnmuumH mEMm may mg UmonHOM OGMME GESHOU HHOm EUOOH Hmm monomm .mm mceoHu OOOH u mcMHumcmm .M.OOm H .mm mWEon + mcMHumcwm .m m HHom nEoOOH Hmm OGMuumcwm .AIOOm “.mcMnumcwm .M HHom Eu OOH Rmmuomm wouMHsomomMM.0 OObH H .mm mSEOHU mmuMHsomomMO mseon O + mcmuumcum .m o u [Houucoo . .mm m580Hw amom nmmm meH OOOH O NO uOOH nHom + mmmuumcmm um MO MO MO MO MO MO MO mCMHumcmm .m ammo noom an coma . nmm nae nmwm .mm masoao MO MO MO MO MO MO MO Honucoo Hwom 580 OOH\\»wMHmcmO whomm ucmEUMmHB vamH NHHH\_ vmm . man mum Nam mmH HUOHQQO mmMO mmummc OwUMHsEsoom OO «O on Om NO ON OH nuBonU mo NMQ mGMmb >>Mc nuHB OmOMHUOOmM msuMHsoHomMO .m O0 muHmcmO muomm .vvdenMB .mm.mmEOHU nam nmm new nmm nmm QMH _ as + mcmuuommm nu MO MO MO MO MO MO MO mcMuumcmm .m owe «ma can ado nmv UHN oam .mm mseoHo MO MO MO MO MO MO MO Houucoo coHuommcH ucmoumm ucmEuMMHB «HmH NHHH vNO OH mHh mvm th mOH AU may mmMO mmummw OmuMHSEsood OO «O on mm. 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I334 MN MO Mm MO Mo Mm MO MO Mm MHH MH Mm nOm MOO onma.MH muuM\mM\nH m OMH usoMemz onMH Mm Mm Mow MN nMO Mmm MHH Mm Ma Mm MNH MM MNm Mo.oH Mqu\nH on MO uuoEMsmz onam MHH Mm MOH Mm an Mm Ma Mm MOH Mm MOH MHH nmm am.OH mqu\nH ON Mm uuosMemz nMHH MO Mm MMH MO nom Mm MM MM Mmm Mm Mam MOH Mmo oam.MH mqu\nm MO uuosMsoz MN Mm Mm Mm MO an MM MOH Ma Ma Mm MNH nmm Mam Mm.¢~ Mqu\MM am m com MMMM>> MN MN Mo Mm Mm an Mmm MHH Mm MO Mm MOH cam Mam M0.0~ mquxfiM am m.H omH mfisma an Mm Mm MN Mo an MM Mm Mm Mmm MN Ma Mom Mwm Mm.- muqufiM OH ma.o MMH xfisoa oam gum nmm nmom now can gem nae nmm nMO nMON nmo chm MOM u~.mm xumco HOMH NFWH OONH\‘OOOH \bmh MOO O osmmHu uoou O 009 .oz HOom\mEoOOH um .02 mqu\u30 mqu uma muMu OcM OH0H> coOuMHOEuoO unwEuMwua wm no OM OOMuumcwa msnocwHOuMnm .HOOOHVOCan >>Mc 50H: pmuMHUOmMM OMMuumcmm manocwHOuMum O0 Houucoo OCM OUHEMMOO COMuMHsmom "OmummHnMB I335 acmvsum 0:» 0» OMHOHOOUM AO0.0 u mO ucmumOOHc OHucMoHOHcOHm no: muM uwuumH mEMm up» On szoHHoO mcMwE assHoo i .ummu «OCMu 0HmHuHOE mHsmx :ME302 * OO0.0 x N OOO I Amsmu .xME + .mEmu .cHEO u OOOH MOMO mmummc vmuMHsfioooM u on « Mm MO MO Mm. MO MO MOm MO Mm MO MO MO MNNH OO0.0N ¢\.H.M nH O.N 0OH xHewa Mm MO MOH nMOH nO nO MOO MOH MO MOH MO MO MHHH OOOH.ON <\.H.M nH O.H 0OH stme MO MOH MOH nMOH MNH MOH MHO MNH MOH MON MHH MNH MOHH OOQON.HN <\.H.M nH O.H 0OH xHama nMOH MON MOO onhm nMOOH MHO MNNH MOH MON anm MOH nOm MHNH onMOH.OH <\.«.M nH 0.0 0OH xHEMB nMHH MO MO nMON MONH nNh MOO MOH MON MOH MOH MOH MNOH nMNO.OH ¢\.HMO O.H OOIOO 0cHouonuuwa MO MOH MNH nMO MNH MOH MOO MOH MOO MOH MO MON MOO UUQHN.NN .OMumm uMfiHoO <\a.M OH O.H Msmm ¢\.M.M nH o.H a muMM>> MO MO MOH nMO MOO MOH MOO MOH MON MNH MNH MOH MOO bMOO.OH .¢\.H.M nH O.H A muMcO> nON anH nONm 0OO nOON oOOH nOON ONO nONH nOO nOO nHO MOHH MHO.OH .xomsu HNNH MOHH OOO NOO OOO OOO HNNH MOHH OOO NOO OOO OOO OON 05mmHu uoou O\.oz HHom mEoOOH\.0z A<\u30O 0u0< O0 muMm UcM «no uM mcMuummwm manocmHOuMum OH0H> coHuMHsfiuom .ucmeuMmuB .AOOOHO mcan >>Mc :uHB OmuMHOOmmM mcMuumcmm .M O0 Houucoo OMM OOHEMCOO :oHuMHamom "OO_O0HQMB BIBLIOGRAPHY 7 . 0 BIBLIOGRAPHY Acosta, N. and R.B. 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