WWWIN!WWI“!VHINH”WWWWW TYIRALB RAISRE MICHIGANS SWE LLLLLLL LLLLLLLL LLLLLLLLLLLLLLLLLLLLLLL LL L L LLLLLL LL This is to certify that the thesis entitled GENETIC AND ENVIRONMENTAL VARIATION IN AN INTENSIVELY CULTURED BLACK LOCUST (Robinia pseudoacacia L.) HALF-SIB PROGENY TEST presented by A’QiBOH G4Y€ has been aece wted towards fulfillment of the Acquirements for M degree in F9 P35 f1“): QLCV/EW Major professor Date 1 l , 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution ”‘3 Lame: L M“ Ff ' i‘; :L . ‘5‘ L‘r .1 qfi It: “$333” «Nae. o E fi-n u Unwe rem! “—- -mw PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE MSU Is An Affirmative Action/Equal Opportunity Institution c:\cIrc\datedue.pm3-p.1 .—.___——- — "v ~—--—-——»——-— ., w v __.. ~ ~- GENETIC AND ENVIRONMENTAL VARIATION IN AN INTENSIVELY CULTURED BLACK LOCUST (Rbbinia pseudoacacia L.) HALF-SIB PROGENY TEST By Abibou Gaye A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Forestry 1991 4324303 ABSTRACT GENETIC AND ENVIRONMENTAL VARIATION IN AN INTENSIVELY CULTURED BLACK LOCUST (Robinia pseudoacacia L.) HALF-SIB PROGENY TEST BY Abibou Gaye Based on results from a germination test in the laboratory involving 16 half-sib families of black locust, 5 fast-growing and 5 slow-growing families were used in a nursery progeny test intensively cultured to evaluate early genetic differentiation in height, diameter, number of branches, thorn length, insect susceptibility, stem form and photosynthetic efficiency. Also, the relationships between nursery characteristics and 4-year field height were investigated. The variation patterns for all characteristics indicate large within-family variation compared to family variation; but family heritabilities were much higher than within-family heritabilities suggesting that substantial genetic gains can be made from family and within-family selections. On the other hand, although 4 good families out of 5 figured among the 5 top ranking families in height and diameter in the nursery, the poor correlations observed between nursery traits and 4-year field height did not suggest reliable prediction of future performance. The effects of seed weight and the implications of the practice of top-pruning black locust seedlings prior to field planting on seedling development were analyzed and discussed. To my son Papa A.M. Gaye (four years old) who did not understand why I was separated from him for two and one-half years. iii ACKNOWLEDGMENTS I would like to express my sincere gratitude to my major professor Dr. James W. Hanover for his valuable contribution in my training through his guidance, support and confidence in my abilities. I would like to thank Dr. Daniel Keathley, Dr. Michael Gold and Dr. Richard Ward for their review and significant contributions in this thesis. Special thanks are extended to all the personnel of Dr. Hanover's laboratory for their help and support throughout the two and one-half years I spent with them. iv TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES INTRODUCTION SECTION 1. FAMILY VARIATION IN SEED CHARACTERISTICS OF BLACK LOCUST (Robinia pseudoacacia L.). SECTION II. FAMILY AND WITHIN-FAMILY VARIATION IN EARLY SEEDLING GROWTH OF BLACK LOCUST (Robinia pseudoacacia L.). SECTION III. VARIATION IN SEEDLING QUALITY FACTORS AND INSECT DAMAGE IN A HALF-SIB NURSERY TEST OF BLACK LOCUST (Robinia pseudoacacia L.). SECTION IV. EFFECTS OF GENOTYPES AND GROWTH POTENTIAL ON GAS EXCHANGE CHARACTERISTICS OF BLACK LOCUST (Robinia pseudoacacia L.). REFERENCES 14 49 63 74 Table Table Table Table Table Table Table Table Table Table Table 10. 11. LIST OF TABLES Physiological attributes of black locust. Seedlot characteristics and 4-year field height for 16 black locust open-pollinated families. Summary of ANOVA for percent germination (in parenthesis, percent of total variation) and correlations among seed germination and seed weight in black locust open-pollinated families. Mean seed germination, mean seed weight and ranking of families in black locust open-pollinated families. ANOVA form and EMS of ANOVA and ANCOVA on an individual tree basis. Total and daily growth rate (cm) between height measurements in a black locust nursery progeny test. Family means, number of seedlings and range of individual tree values for nursery growth character- istics in 10 half-sib families of black locust. Matrix of rank correlations between nursery growth characteristics in 10 half-sib families of black locust. Results from the ANOVA for the nursery growth characteristics based on 10 half-sib black locust families comprising 5 good and 5 poor families. Variance components, percent of total variance in parenthesis and heritability estimates for nursery growth characteristics in 10 black locust half-sib families. Phenotypic (between-family, within-family and total), genotypic and replicate correlations among growth characteristics in a black locust nursery progeny test. vi 11 12 19 21 27 28 29 33 37 LIST OF TABLES (cont'd) Table 12. Table Table Table Table Table Table Table l3. 14. 15. 16. 17. 18. 19. Family mean correlations of seedling growth characteristics in the nursery with l-, 2- and 4-year field height, with percent germination and with seed weight of 10 families and in parenthesis of 8 families of black locust after deletion of 2 unstable families from the 10. Expected mean squares for the ANOVA based on individual-tree and plot mean basis (adopted from Foster, 1986). Mean squares, variance components, percent total variation in parenthesis and family heritability estimates of insect incidence and stem form in a black locust nursery progeny test. Mean insect incidence and stem form and rankings in the nursery for 10 open-pollinated black locust families. Correlation matrix between insect incidence and stem form components; and correlation coefficients associating insect incidence and stem form with nursery growth characteristics in a black locust progeny test. Means and summary of ANOVA in 10 open-pollinated families of black locust for late season net Pn, stomatal conductance, transpiration, and late season height in a nursery progeny test. Family means and percent of overall mean for late season net Pn, stomatal conductance and transpiration in a black locust nursery progeny test. Correlations between physiological characteristics and nursery growth characteristics, and field height in 10 open-pollinated black locust families. vii 4O 52 53 57 59 67 68 7O Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 5a. 5b. 5c. LIST OF FIGURES Percent germination for 10 seedlots of black locust, 5 days after sowing in the laboratory. Daily growth rate, curves of 10 half-sib black locust families, from sowing to end of growing season in a nursery progeny test. Growth curves of 10 half-sib black locust families from sowing to end of growing season in a nursery progeny test. Height growth curves of 5 good and 5 poor half- sib families in a black locust nursery progeny test. Age trends in variance components of height growth in a black locust nursery progeny test. Age trends in additive genetic (Va), environmental (Ve) and phenotypic family (Vp) variances of height growth in a black locust nursery progeny test. Age trends in individual, family and within-family heritabilities of height growth in a black locust nursery progeny test. Correlations relating nursery height and diameter to field height for 10 and 8 black locust open- pollinated families. Insect incidence and seedling form in an intensively cultured black locust progeny test. Correlation of average 2 poor stem form of seedlings with average 1 seedlings injured by insects in an intensively cultured black locust progeny test. viii 22 25 26 30 30 30 44 6O INTRODUCTION Black locust is one of the most widely planted species around the world (acclimated in most temperate and mediterranean zones of the world) because of its remarkable attributes (Table 1), its ability to utilize a wide range of sites and its multiple uses such as timber, posts, firewood, apiculture, fodder and erosion control. The species is frequently propagated by seed for economic reasons, but can be easily propagated by root cuttings (Swingle, 1937) and by tissue culture (Keresztesi, 1983; Davis and Keathley, 1987), and thus, its potential for further improvement through cloning and hybridization is great. However, in the U.S.A. where it is native, little attention has been paid to the silviculture and breeding of the species for commercial purposes until recently when fears of petroleum shortage prompted biomass energy research. Thus, comprehensive germplasm collections of half-sib families from the natural and naturalized range in the USA and southeast Canada have been made by Michigan State University (MSU) and the University of Georgia since 1983. Analyses of growth and phenological characteristics from provenance tests in Georgia (Kennedy, 1983) and progeny tests in Michigan (Mebrahtu and Hanover, 1989) have shown no geographic patterns of genetic variation but revealed variation among and especially within families. Therefore, it has been suggested that there is a need for progeny tests to select among and within the populations for genetic improvement of the species na- :— .I L A . .. l — . Table 1. Physiological attributes of black locust. - Rapid growth rate, out-competes weeds - Indeterminate growth habit - Nodulated roots, fixes atmospheric N2 - High density wood - Good pulping qualities - Highly resistant to decay fungi - Tolerates low fertility sites - Resistant to drought stress - Resistant to air pollutants - Resistant to low temperatures - Resistant to high temperatures - Very high net photosynthetic rates - High light saturation - High leaf area accretion rate - Long leaf retention time - Low stomatal diffusive resistance - High transpiration rate - Rapid leaf position adjustment to changes in light intensity - Small leaflets minimize self-shading - Vigorous sprouting of root cuttings - Very plastic root system: strong tap and dense fibrous upper roots - Flowers at early age — Produces abundant seed crops - High seed viability and longevity - Seeds easily cleaned, stored, sown - Seeds germinate rapidly - Easily micropropagated - High leaf protein - Much genetic variation IN: Hanover, J.W. 1990. Physiological genetics of black locust (Robinia pseudoacacia L.): a model multipurpose tree species. Proc. Conf. on Fast Growing and Nitrogen Fixing Trees, Univ. of Marburg, W. Germany, 1989. 3 for traits reflecting growth characteristics, stem form and damaging agents. Since tree breeding, usually achieved through progeny testing, is a long-term process requiring labor, space and money, theLbasic objective of tree breeders has always been to achieve selection as early as possible, i.e., before the economic maturity of the trait of interest, resulting in shortening the breeding cycle and hence, reduction of direct costs (Magnussen, 1989a; Namkoong et al., 1988). Thus, early selection, particularly in species such as black locust exhibiting substantial growth at early stages of development, will result, if proven efficient, in maximum genetic gain per unit of time (Magnussen, 1989a; Namkoong and Conkle, 1976). Keeping this general strategy in mind, the following study was designed to investigate the response of black locust open-pollinated families to early selection through laboratory and nursery trials and comparisons with field performance by pursuing these specific objectives: 1. To determine the kind and amount of genetic variation for seed germination, growth, insect damage, stem form and physiological (photosynthesis) characteristics in 10 open-pollinated, progeny tested seed sources of black locust. 2. To examine the relationships between seedling growth characteristics in the nursery and seed weight, seed germination, field performance (first-year, second-year and fourth-year height). 3. To discuss the extent to which nursery bed selection may be reliable with regard to studied traits. 4 The trait emphasized in the study was height growth because it is a primary component of commercial growth and its pattern changes can be readily analyzed (Namkoong and Conkle, 1976); but since it can be associated with undesirable characteristics (thorniness, damaging agents, poor form), attempts were also made to assess the relationships between growth and other characteristics. Indeed, characteristics can be closely or loosely, positively or negatively interrelated and thus, progress from selection is dependent on the nature and extent of the interrelationships found between characteristics (Matziris and Zobel, 1973). SECTION I. FAMILY VARIATION IN SEED CHARACTERISTICS OF BLACK LOCUST (Robinia pseudoacacia L.). ABSTRACT Eight fast-growing and 8 slow-growing half-sib seedlots of black locust were used in a germination test for the purpose of selecting 10 rapid germinating families (5 good and 5 poor) to be used in a nursery progeny test. Five days after sowing (following pretreatment of seeds in H2804 for 50 minutes), the germination percentages per family ranged from 47.70% to 98.17% with 88% versus 83.60% for good and poor families. The ANOVA showed significant differences among families (P<0.0l) but no statistical differences were found between good and poor families. On the other hand, the correlation results indicate that seed weight did not, apparently, influence seed germination. INTRODUCTION For tree breeding to be successful, rapid and uniform germination of seed in the nursery is required; that is, factors influencing germination such as seed dormancy, seed characteristics (size, weight, age) and genetic factors need to be identified. For hard seeds such as those of black locust, it is well known that the primary factor responsible for delayed germination is the dormancy induced by an impervious seed coat rendering seed difficult to germinate under favorable conditions of temperature and moisture unless pretreatments (water, acid, or mechanical) are done to soften the seed coat prior to 6 sowing. However, aside from the seed coat dormancy, seed characteristics (seed size, seed weight, age) and inherent factors may control the rate of seed germination and thus represent potential factors in delaying or accelenatingsseed.germination. The following germination test was conducted in the laboratory for the purpose of selecting among 16 seedlots, 10 rapid germinating seed sources to be used for direct seeding in the nursery. We also wanted to determine the relationships between seed germination percentage and seed weight. MATERIAL AND METHODS Sixteen half-sib seedlots were used in the germination test and comprised 8 known fast-growing families (good families) and 8 known slow-growing families (poor families), distinguished on the basis of height measurements made in 1989 from a progeny test including 393 families established in East Lansing in 1985. From the height measurements (1989) the top third and the bottom third families were considered, respectively, as good and poor performers in the field. The respective height ranking from the progeny test of the 16 families used in this study is given in Table 2. All seedlots used for the germination test were collected in 1984 except for 2 seedlots which were collected in 1989 (Table 2) but from the same trees in which seed were collected in 1984. Seedlots were stored in paper bags at 19C. On May 15, seeds from each of the 16 seedlots were pretreated by immersion in concentrated H¢SOQ for 50 minutes, then removed and rinsed thoroughly with water, and set to germinate in trays containing moist cotton covered by filter paper. The test was carried out with two .umou hsowoun on“ mo moHHHaom mom onu ou obauoaou moaaaaom ed on» How wnaxnou u A . .moaaaaum ma on» How waflxcon u a .eaaflm «nu ca nuaouw unwaon Hoohuq can: woman .%H0>Huooamou .mowawaum noon .moHHHSwm Doom n mm .muxm «mm ca oo.nu¢ mad m>.H ¢Q-N mm Hae cum NH n¢.na¢ nma wo.a «mum mm mow «an a 00.no¢ «ma mo.a amuu mm mam chm AH on.na¢ woa on.H owuaa mm mmm «on ma on.mhm nma om.a «mum hm mum emu ma m¢.acm nHH aw.a #wum mm mum omw ma no.0am nNH mo.~ «mIN mm man «an «a mw.mhm flea mn.a cw-~ mm can mm o mN.HHn wad «o.H ¢mum mu Ham we m mm.man had oa.N «QIN mu mam ma m om.mw¢ mad ¢~.~ «mum mu «an me n oo.oam and m¢.~ «m-~ mu «mm «a H oo.moo ema mo.N am-HH we own mm a nn.wam ooa mm.~ «Qua me man ma N om.amm «NH em.a amuu mo awn mm m mm.m¢m «ma ao.~ «muw mu Nam connoh va , .uauaom aeoom mecca noau Aunwfiom you 9.3 final mo .02 OOH mo nooHHoo 90H How Judd Jada madam Module Hduoa unwaon_ mo ouun \flomhh [Doom .mofiawamm woumcfiaaom-como umdooa Momafi ma non uswwon oaowm umo%-¢ Dam mowumwuouomumno uoacoom .m oHan 8 replications at 25°C and continuous light. Germinants were counted during 3 consecutive days beginning 2 days after sowing to furnish the data for the calculation of germination rates. Count of germinants were stopped the 3rd day because germination was nearly completed in most seedlots. In addition, for each seedlot, 100 seeds were weighed to estimate seed weight. Percent germination data were subjected to an ANOVA using replication means following arcsine transformation of the percentages. Duncan's multiple range test and the family mean heritability were calculated as well as correlations associating rank and means of family seed weight with, respectively, rank and means of family percent germination. RESULTS AND DISCUSSION Variation in seed germination Mean percent family germination is given in Table 4 and illustrated in Figure 1. Five days after sowing, germination percentages per family ranged from 47.70% to 98.17% around a general mean of 85.88%, indicating a high germination rate which is highly desirable for nursery production. Seed from the 8 good families had a higher germination rate than those of the 8 poor families (88.00 vs. 83.60%), but in the 10 families selected for the nursery test (Table 4) the 5 poor families had a slight advantage in germination over the 5 good families (90.50 vs. 88.50%) because 2 rapid germinating good families were not retained for the nursery test due to lack of available seed. .63 509:: m5 5 now: 35th H * .boyotono. 9: E 9:38 tote mxop m .umzoflxooz to 30:58 or not cozoEEtoo Lcootod é 0.39.1 850w Doom _ i 3 wow 1.me in?» .62... mun Kan 0:” 3mm +mwm. awn *Nmn sown $3” 3% NmN moEES tooa s§$ mmEEE Doom § ON 00 00— ON— uououguueb iuewed 10 The ANOVA (Table 3) showed significant differences among families (P<0.01 for the 16 families and P<0.05 for the 10 families) but no differences were found between good and poor families either at the level of the 16 families or at the level of the 10 families. Family differences accounted for about 75% (16 families) or 63% (10 families) of total variation, explaining the high family heritability observed (Table 3). The decrease in family heritability in the 10 families versus the 16 families is due to the decrease of genetic variability in the 10 families as a result of selecting for higher germination rates. The error variance accounted for the remaining variation since variation due to replication was negative and hence, estimated to be zero. Effect of seed weight Average seed weight by family varied from 1.68 g/100 seeds (16.8 mg/seed) to 2.88 g/100 seeds (28.80 mg/seed) with a general mean of 1.98 g/100 seeds (19.80 mg/seed). This is somewhat consistent with the results reported by Pathak et a1. (1978) who found a variability ranging from 11.02 mg/seed to 26.73 mg/seed in 5 seedlots of black locust. The good families outweighed the poor families in either the 16 families tested or the 10 families selected for the nursery trial (Table 4). The correlation coefficients calculated between average seed weight or rank seed weight per family and mean percent germination or rank germination per family (Table 4) were low and either positive (16 families) or negative (10 families) suggesting that seed weight did not, apparently, influence seed germination. In contrast seed weight is reported to influence strongly seed germination in sweet gum, white spruce and slash pine (Franklin, et a1. 1981), and in bald cypress (Faulkner and Toliver, 1983). 11 3:52.03 to .33 85 on 28:22... .3 c2 + C. c: .. c. an totem Co 325 “EV co_uao_.aom outzom ¢soa< 0:» gov not cool tau u 2. 3:330: to 12,3 35 s 2858.; u .. ucnu_w_cmmm uoc u we .IIIIIIJI agape: noon wn~.o mm~.o scat .m> comuncmlcou too» new. ugumo: mko.o 0m~.o noon .n> comuucmlcou noon cool uucomuo.0ttou Cup: E... Red 335:2... bi: nx<~.onvmh.~w --. omn.- Axon.m~v m~.o~ -- m~.o~ mp Locum -- . m: - -- -- mc -- P Loom .n> zoom Axo~.nov wr.ow. c¢¢.¢ -F.Foe Aan.¢nv Np.oh capo.o no.mwF my >Lmluu new o>_uoooc m: ~¢.o ~mo.o now o>muomoc m: «m.o Nm.- F co_uou_.nou . onward moccamua> .umou a cool moocamea) «now a ocuawa :99. wt 8:3: .332 2 8t 83.528 a 8:3: 2. :a .8 SEE-:8 u .moumsvm coma pouoomxo Dam .mowawamm woumaflaaom-aomo umDooH xooan ca uanoB town one fiofiuocwauow Doom mcoam maowumaouuoo Dam .AcowumHnm> Hmuou mo uaoouom .mwmonuaoumm CHV aowumCHauow unmouom you <>oz< mo %umaasm .m manna Table 4. Mean seed germination, mean seed weight and ranking of black 12 locust open-pollinated families. All 16 Families 10 Families Used In Nursery Tests Seedlots % germination Seed weight(g) % germination Seed weight(g) mean rank 100 seed rank mean rank 100 seed rank 411* 98.17 a 1 1.73 12 98.17 a 1 1.73 8 384 97.00 ab 2- 2.24 3 - 375* 9633 abc 3 1.80 10 96.33 ab 2 1.80 7 391* 94.00 abcd 4 1.92 9 94.00 abc 3 1.92 6 348* 93.96 abcd 5 2.88 1 93.96 abc 4 2.88 1 398* 89.68 abode 6 1.68 15 89.68 bed 5 1.68 10 382* 86.50 bcde 7 2.48 2 86.50 bed 6 2.48 2 344 84.56 cde 8 1.94 8 380* 83.12 de 9 2.06 7 83.12 cd 7 2.06 5 385 * 82.50 de 10 2.10 4 82.50 cd 8 2.10 3 383* 80.00 de 11 1.70 13 80.00 d 9 1.70 9 347* 79.25 , e 12 2.08 5 79.25 (1 10 2.08 4 408 79.18 6 13 1.68 15 310 77.00 c 14 1.75 11 282 74.62 c 15 2.09 5 373 49.50 f 16 1.69 14 All 85.88 1.98 89.60 2.053 families Good 88.00 2.21 88.51 2.308 families Poor 83.60 1.76 90.50 1.798 families *Families used in the nursery test. Means with the same subscript are not different at the 0.05 level of probability using Duncan’s multiple range test. 13 CONCLUSION It appears that, when properly pretreated and allowed to germinate under favorable conditions, seed of black locust will germinate well and rapidly but will also exhibit significant differences among genotypes. Nevertheless, the data failed to show significant differences in germination among the known fast-growing and slow-growing families. The results also indicate that percent seed germination is quite independent of seed weight. Thus, seed weight will influence the early performance of black locust seedling height growth but the effects are random with respect to longer term performance of progenies. Therefore, seed weight cannot be used to adjust for first-year growth rate when comparing genotypes for early performance. SECTION II. FAMILY AND WITHIN-FAMILY VARIATION IN EARLY SEEDLING GROWTH OF BLACK LOCUST (Robinia pseudoacacia L.) ABSTRACT Ten genotypes (5 good and 5 poor) of black locust were progeny tested in the nursery to: (1) investigate early genetic differentiation in height, diameter, number of branches and thorn length; and (2) assess the relationships between nursery growth traits, seed weight and 4-year field height. Total height in the nursery averaged 99 cm to 128.8 cm per family with 114.3 cm and 110.6 cm, respectively, for good and poor families. However, the ANOVA detected weak family differences (P<0.1) and none for good versus poor families. On the other hand, family differences were much stronger in diameter (P<0.05) and number of branches (P<0.01). The variation patterns for all growth traits were characterized by relatively little family variation and a large amount of within-family variation; but, the family heritabilities were high compared to within— family heritabilities. Seed weight showed significant relationships with diameter, number of branches and thorn length in the nursery and exerted an important effect on 4—year field height, masking thus, variation in inherent vigor. Therefore, selection should be delayed until after seed effects have ceased. Results also indicate poor correlations between nursery growth traits of the 10 tested families and 4-year field height of the same 10 families although 4 good families out of 5 were included in the 5 top 14 15 ranking families in the nursery. However, these poor correlations are thought to result from the top-pruning of seedlings prior to field planting. INTRODUCTION Sluder (1983), Robinson and Van Buijtenen (1979) have reported various studies based on conifers (Zobel et a1., 1977; Zaeger 1965; Hunt 1967; Grisby 1975) showing that substantial improvement in growth rate can be made by selecting outstanding nursery seedlings. However, these studies were based on mass selection, i.e., selection of best seedlings regardless of seed sources, which is different from selection among families in progeny tests (Sluder 1983) where genetic effects are to be separated from environmental effects. Thus, as pointed out by Rehfeldt (1983), reliable results in the nursery will require intense cultivation (weeding, spraying, fencing) to control extraneous environmental variation in order to test under conditions in which the phenotype is more a function of the genotype than the environment. But, since genes involved in trait expression in one age or environment may not be the same in another age or environment (Namkoong et a1. 1988) assessing the degree of relationships existing between early and later plant characteristics is required to determine whether or not early seedling characteristics can reliably predict future growth. To my knowledge, genetic studies of black locust based on nursery progeny tests have not been done, and thus, this following study is intended to provide a necessary basis for forecasting relationships between juvenile and mature characteristics. 16 MATERIAL AND METHODS Nursery procedures. Seed fromtthe 10 seedlots selected for the nursery test were hand- sown (June 15) after stratification (50 minutes in H2804) across nursery beds in a single soil series characterized by good internal drainage at the Tree Research Center at Michigan State University. The experimental design was a RCBD with 4 replications of 80-spot rectangular plots (4 rows of 20 sowing spots each) and spacing was 45 x 33 cm within-plot and 110 cm between plots. The plots were fumigated and leveled prior to sowing; the sowing depth was approximately 2 mm and about 2 seeds were used per sowing spot, i.e., 160 seeds per plot or 6400 seeds total. A germination count conducted 7 days after sowing (June 23) and based on well established seedlings (at least 2 leaves well developed) has shown good results and thus, consistent with the germination test results from the laboratory. A week later seedlings were thinned to one per emplacement and few transplants were made. Throughout the growing season, the plots were hand-weeded, sprayed with insecticides and watered when necessary, and protected by a fence. However, blocks 3 and 4 were attacked and apparently randomly damaged by rabbits a few days after thinning, prompting the reinforcement of the protective fence around the nursery experiment. Though most of the seedlings maimed by rabbits flushed again, only about 50 seedlings out of 80 per plot (> 2000 total) were selected for observations and measurements by excluding the disadvantaged seedlings (damaged seedlings plus transplants). 17 Characteristics measured Height measurements were made to the nearest centimeter at 40 days (July 26), 63 days (August 18), 82 days (September 6), 108 days (October 2) and 137 days (October 31) after sowing with the last measurement occurring after the seedlings had shed their leaves. Also after the growing season, diameter was measured to the nearest millimeter at ground line, the number of branches per seedling counted, and thorn length scored by a visual estimate according to the following procedure: 0 - 53 mm; 1 = 3 to 10 mm; 2 - > 10 mm. Statistical and genetical analyses All growth traits measured on seedlings were subjected to an ANOVA on an individual seedling basis, assuming the following random linear model: yijk = u + R1 + Fj + (RF)ij + Eijk where yijk - performance of individual k from population j in block 1; u = overall mean; Ri = effects of the ith replication (i = 1, 2, ... 4); Fj = effects of the jth family (j = l, 2, ... 10); (RF)ij = effects of the interaction between the ith replication and the jth family; Eijk deviation of seedling k from the effect of population j in replication (= within-plot error). With the assumptions that families are half-sib and that epistasis and dominance are ignored (Namkoong et a1. 1988), than family effects are considered to estimate 1/4 of additive genetic variance, and within- 18 plot error effects 3/4 of additive genetic variance plus environmental variance. The form and expected mean squares of the ANOVA as well as the expected mean cross products of the Analysis of Covariance (ANCOVA) are given in Table 5. Variance estimates (replications, family, family by replication interaction and within-plot) and narrow sense individual, family and within-family heritabilities were calculated and means were separated by using Duncan's multiple range test whenever the ANOVA appeared significant at 0.05 level of probability. In addition, total (individual), between family, within-family and additive genetic correlations relating growth characteristics were calculated as well as family mean correlations associating growth characteristics with seed germination, seed weight and field height (1-, 2- and 4-year). Expected genetic gains were not estimated because the heritability values were based on few genotypes growing on a single site rendering their use in predicting genetic gains of limited value (Hicks et a1. 1977). All analyses were made using the Statistical Analysis System (SAS Institute Inc., 1985) and figures were obtained from Plotit (Eisensmith 1985). RESULTS I. Height growth 1. Patterns of height growth Figure 2 illustrates the estimates of daily growth rates as presented in Table 6 and can be summarized as follows: From June 15 l9 .Ammmflv .Hm um wcooxamz scum amummea uoam\mmGHHUoom mo Hones: coma owfiofihmfi I u moHHHamm mo nomads I m mnofiumowamon mo Hones: I u H-umu qooz< <>oz< umou m m: we oouaom mam axon <>oz< .mump menu HMDDH>HDGH Go momma A<>oozoo mo wwmhamcm one <>oz< mo AmZMV moMmSUm some vouoomxo use autos A<>oz mo mwmkam¢< .m manoH 20 (sowing date) to late July, height growth was relatively slow (2.6 mm to 3.45 mm per day per family); then it increased rapidly during August and peaked at early September (18 mm to 24 mm per day per family) before decreasing sharply and nearly ceasing in late September. The residual growth observed in October averaged less than 1/2 mm per day per family. The slow growth rates observed during July may have been due to adjustment of the genotypes in the environment and/or development of an efficient root system prior to aerial expansion. Overall, the daily mean growth per family varied from 9.30 to 11.80 mm around a general mean of 10.42 mm. The known fast-growing families (good families) average 10.58 mm per day versus 10.26 mm per day for the knoWn slow-growing families (poor families) while the individual tree values varied from 1.44 mm to 19.5 mm per day. The residual growth accounted for little in total growth since, at the end of September, the proportion of total height growth completed by families ranged from 97.60 to 99.50% with 98.80% versus 98.50%, respectively, for good and poor families. Similar patterns of height growth in natural conditions were reported on black locust by Jester and Kramer (1939) whose results from greenhouse and field experiments showed that long days allow continuous growth while short days result in onset of dormancy in black locust. Wareing (1954 in Kennedy 1983) speculated that the photoperiodic receptor, growth inhibitor substance, is manufactured in mature leaves under short day conditions. However, Waisel and Fahn (1965 in Kennedy 1983) indicated that cambial activity was influenced primarily by T°C. The cambium appeared to be 21 pcoEouuna Aswan: gape» - any ”menu ca Ha>uoucaVucoEouona Sandor u A can .532 13:: u in noon» Huana>wona kHs.A-saA.o ooo.u-oo.o Ho.~-oo.o oos.m-nna.o oo.m-oo.o nus.o-n~o.o «0 omnau 9.308 noH.H-~so.o sno.o-H~o.o am.a-ma.o ne.~-am.fi om.fi-ma.o osm.o-~o~.o sadaau uo omega ouo.H on.sa mmo.o as.” oNH.H ma.m~ nH.N om.oq an.” as.s~ os~.o ao.HH «sacs unaudflaau Hoom moon» Husva>avafi no.H-s~.o H4.H-oo.o Ho.~-oo.o nan.s-noa.o o~.m-oo.o nuk.o-n~o.o «0 omega @508 osH.H-ono.o Hno.o-oso.o ~n.~-mo.~ k~.~-um.fi ~on.a-~mm.o oom.o-km~.o Aguaau uo omega ono.a mo.~oa 44°.o m~.H o~.H mm.~n AH.~ sfi.oa ~«.A nH.m~ mw~.o an.HH mecca "quHAaau coco noouu Hoaoa>auaa no.H-¢aH.o H¢.H-oo.o Ho.~-oo.o Hm.s-noa.o ou.m-oo.o nes.o-n~o.o mo omnum agon— oH.H-ono.o ano.o-a~c.o on.u-ono.o ne.u-oo.fi on.a-~mw.o oan.o-flsfl.o mafiauu no annex ~4o.a na.ao~ qu.o ooA.H noA.H ko.Hn nnH.~ en.oe o-.H oo.m~ nm~.o um.HH aqua: sHo.H as.om Hmo.c com.o cmo.a oo.o~ no~.~ Ha.fis ~N~.H Ha.o~ ~o~.o mq.ofl ”as sko.o oo.¢m nn°.o ano.o mac.a om.k~ onH.~ cc.oq smo.a ¢~.n~ on~.o nN.oa won nno.a oa.~oa oco.o 0H.H mun.a Ne.en ooo.~ «H.on ~aa.a as.s~ so~.o Hm.HH Han onm.o no.0s neo.o a~.H na~.H Afl.un kas.u ¢¢.on «mo.o on.o~ sm~.o on.a nun ~aa.o H¢.Ha ano.c as.” soA.H oo.an wmo.H no.0» mmm.o Ho.H~ HaH.o no.5 new mNH.A om.ooa Hmo.o as.H Hon.H no.an onfl.~ no.os na~.H A¢.~N mm~.o nA.AH «mm o¢A.H on.HHH neo.o n~.H mm~.H sa.~n ns~.u m~.mq ~on.a on.sm nom.o H~.~H own moo.o om.no ono.o oe.a oms.o mfl.¢~ ono.u on.mn can.” Hm.an oam.o oa.NH nan mac.” nn.ao nao.o as.“ nmo.H ma.o~ was." mN.Hs mam.fi nm.on oom.o om.~H as” noH.H no.nHH Huo.o «Ho.o osm.A so.nn nns.~ Ha.os ~a~.H No.~m osm.o «o.mH he» nuvxoacu Hagen nue\oa¢u Adana nuvxouau Hagan hvuxouau Hanan nuvxou-u annoy haexouou Adana Ran accrue Ruse. nan upon» ago. as Doors anew. A» unvmuaa undo .oa unqunu have. sou museum” ensue anal-m 22E 88.4: SS4: 354: 83.:— S: in .umou maowoua muomudc umdooa xoman m aw Aaov mums £u30uw unwwon hawmp one HMDOH . 0 0.3mm. .:¢.mmm.mm .m vam H mezEE Loom ”mefimmdmmdewLVM H mmEEB boom 9 58 E E; 22 .53 cm 3: o E 6088 306 v8 Ucm ow ow Eot .mflzES $302 x003 £mltoc or v6 mezzo 30‘. £29. 360 .N 950E mwov :28 goo 88m $93 83., 9:2, _ . _ _ _ _ .x 2.- IO 1 1m U: I low m. N w. m e I TWP w e W \mw/ T ION W WI» I I I 1 mwm «La. mmm I 1mm 0mm Elm mum Ill ®¢M GIG Nfim 9W0 23 active under short day conditions and 28°C/20°C day/night temperatures, and became dormant under 18°C/12°C day/night temperatures. Therefore, the effect of short day photoperiod in inducing dormancy in black locust may be inhibited by T°C. 0n the other hand, Figure 3 illustrates the family growth curves and their rank changes over time. Growth curves are similar in shape (sigmoid) and are characterized throughout the growing season by fluctuations in rankings, indicating that the families did not perform consistently relative to each other over time. However, the rank correlations (Table 8) performed to quantify the degree of association between family mean rankings of height at different measurement ages proved significant in all situations. Further, the correlations increased in significance over time indicating that rankings were more steadily maintained specially after 82 days of age. In fact, as indicated in Table 7, the patterns of rank changes showed a certain stability in family ranking throughout the growing season: 2 families (1 good and 1 poor family) were consistently at the top level whereas 3 families (1 good and 2 poor families) were consistently at the bottom level. 2. Variance trends and heritability estimates 2.a. Variance trends. The results of the analysis of variances performed on all height measurement ages are given in Table 9. There were highly significant differences for replications and family by replication interactions at all ages whereas significant but small differences among families (P<0.1) were detected only after 82 days of seedling age while the good and the poor families showed no significant 24 differences at all ages (Figure 4). For the residual growth, only family x replication interaction showed significant (P<0.05). Variance components are given in Table 9 and their trends were plotted over age to examine their pattern changes (Figure 5a). 2.a.1. Familz variation. The main effect of family increased steadily through time, accounting for 0 to 3.03% of total variation. It reached its maximum absolute value at age 108 days coinciding with the end of the active growing season, and then declined slightly during the residual growth period to account finally for 2.76% of total height variation. On the other hand, the within-family variation contributed without exception for most of the variation associated with height at all ages. It accounted for 42.62 to 71.35% of the total variation and its trends appeared similar to those of the main effect of family variance. Within-family variation includes both environmental factors (microsites) and additive genetic effects that cannot be separated, but in segregating families a sizeable genetic component can be expected (Ying and Morgenstern, 1979). That is, if family selection is to be made in the nursery stage it should be followed by within-family selection in order to achieve more genetic gain. These results on family variation are consistent with previous findings on black locust showing relatively little family variation and a large amount of variation within-family (Kennedy 1983; Mebrahtu and Hanover 1989). 25 :Ymmmfimmmnmfivm M 92:88 Loon ”Pom.mwm.mwm.o mamvm bowls: #262 x83 0 E cowoom 9:38 smog. €008 8.2:..8 poom .8 vco 8 9:38 E0: 62:an $302 xooB £mlto; or .5 $230 £29m £90; m>:o_3E:o .m PSOE wmn . mun.PTvmnnullllllllllll. 3mm 1 awn . owna h¢n 1838 ...lnlll||\\ w\\ u .\. 98v 5 oo< ow ION 19. low low IOOF ION? 10¢? (wo)1qfigeH 26 .7on no m améo; so 2:82 Son 9.6 @000 ocoEo moocotmatp €08.53? 0: H m: .....Hmow xcoootq E85: 6300. .503 o E mo___E8 Q m vco pooo m to $230 £308 390; 3:23:50 .v 9:0: 92% E 02 09 02 om 8 9. om 6.6 row IOOP ION? 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DOPE: “252 x83 >582. .262 1993 a E. 526.3 Ego; so 03:210., Aa>w EEO £29.23 o F. 5330 20.6: Ha 85:09:00 occurs) E. "can: 03‘ .Acv m 320E cca.Ao>V_BcoE:o:>co 405 03239 25.23 5 not»: 00 AA 0 83¢ x vo< n on 5 {av .... 094. 9. H H H o _ . 8 o 8 S 2.2.3—ofio: 8. 3 3 Z 3 3 3 ...—.3 ow ~.3 4...‘m._ cm. a . . . . p . . _ . H > H . . CIYIIIIIIIIII 3E0.— \\ v ul|lullllll|l ..ozafiif a $8 9 a 39033.: x a E — H n a '8. o u c a I . u a -8. > 1 £55755} 31 2.a.2. Family x replication interaction variation. The family by replication interaction was highly significant for all height measurements including residual growth and accounted for 22.37 to 37.57% of the total variation. From ages 40 days to 108 days old, though the interaction variance increased in absolute terms, its relative magnitude showed a steady decline from 37.57% at 63 days to 22.10% at 108 days (end of active growing season). The significance of the interaction effects reflects the failure of the genotypes to perform consistently from one replication to another due to random environmental differences among replications (damaging agents, i.e. insects, rabbits; variation in soil moisture and fertilization, etc.). As a result, interaction effects decreased the capability to detect inherent genotype differences. It seems that from age 40 to 82 days (non-significant family differences) and to some extent the following ages (significant family differences at P Uflumgmw 0>HUHUUN "4ND HNO N \N \— NS. .H.D. . .L. H. M N; 3 HM H moi. Noi.No .mmHHHamm QHm-MHm3 a \< H .m H . . . n o o H pH H muHHo oouu m: H>H :H H macaw oocmHum> onhchosa “hub umoq N N Ni .H.n . S H p. .p . N: .mmbH .Hw um umfium aoum omHSEHom mucofiomaoo kuHHHfimuHuom omo.o omo.o nHN.o HNH.° mmH.o mno.o Hmo.o o as «us.o saw.o ono.o HHn.o osm.o moH.o nno.o o c: sto.o oom.o amn.o NNH.o an.o unqo.o memo.o o r: "HHSHH ImuHHom Hauov Ho~.nmc nHHn.o Aso.NHc mos.o~ Ham.HHc mHHm.o Ham.soc N¢.Hao Hmn.noc su.om~ Asm.nnc m~.n~s HNH.nsc wo.~nH Asm.~¢c Hm.mH uon-:HnuHx H:%c HHEam HqH.mv HNHo.o Hom.Hc woo~.~ Hmw.MHc Hoo~.H Ann.-c He.osu HOH.-V om.s¢~ HmH.an nH.N¢~ HHn.an Hm.s~H Huo.an uo.HH n max 13c HHo.Hc anoo.o Hoo.oc .. 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These results suggest that, with selection based on height growth, genetic gain is possible but progress would be more rapid for family selection. The individual-tree and family heritabilities calculated here for total height (0.122 and 0.317, respectively, in East Lansing) in the nursery were much lower than those reported by Mebrahtu and Hanover (1989) (0.74 and 0.48, respectively, in East Lansing) for first—year field height of black locust genotypes. However, their field heritabilities were, (1) based on plot means and, thus, were inflated by excluding within-family variance from the denominator (see formulae, Table 10), and (2) calculated over 400 families including the 10 families used in the nursery test. Thus, again, heritabilities should be interpreted with caution. II. Other growth characteristics: diameter, number of branches, thorn length Measured at the end of the growing season, diameter, number of branches and thorn length averaged per family, respectively, 9.96 to 11.84 mm, 3.28 to 10.26 and 1.26 to 1.57 (score) (Table 7). Diameter and number of branches exhibited significant differences among families (respectively, P<0.05 and P<0.01) and for the interaction effects (P<0.01) but not for replications while for thorn length, no 35 significant family differences were detected but the interaction and replication effects were highly significant (Table 9). For diameter, number of branches and thorn length, the variance associated with within-family accounted for most of the total variation with, respectively, 77.40%, 72% and 93.30% of total variation whereas variance components associated with families were rather high for number of branches (20.15%), somewhat important for diameter (over 7%) and small for thorn length (1.04%) (Table 9). The heritability estimates along with the genetic effects for diameter and number of branches were much higher than those obtained for height, suggesting that selection based on diameter may lead to more genetic gain than selection based on height. The rank correlations associating total height with diameter and number of branches (Table 8) were high and significant (respectively 0.72 and 0.84), as was also that associating diameter with number of branches (0.79), indicating close family ranks between the three characteristics. In fact, the 5 top families (4 good and 1 poor) for final height were the same for diameter and number of branches. In contrast, the rank correlations relating thorn length to total height, diameter and number of branches were all negative but non-significant except for diameter. III. Correlations 1. Relationships between nursery growth characteristics The correlation coefficients between height growth measurements at different ages were high, positive, of similar magnitude at the levels of total, between-family and within-family (Table 11). These 36 correlations decreased with more distant age pairs and the high within- plot correlations are largely because the variation in size at younger ages are maintained as populations become older (Lambeth et a1. 1983). In addition, the genetic correlations, whose estimates are based on genetic effects, were positive, usually greater than the phenotypic correlations and in some cases they exceeded one. Correlations of more than one are explained as due to sampling error and some invalid assumptions upon which their calculations are based (Rink 1984). On the other hand, the correlations associating total height, diameter and number of branches were also high and positive at the level of total (individual), between-family and within family. The genetic correlations and the total phenotypic correlations were about the same magnitude for height and diameter while the genetic correlations appeared much higher than total phenotypic correlations for total height and number of branches, and for diameter and number of branches. The number of branches per family was more related to diameter than to height. These results indicate that simultaneous selection for rapid height growth, large diameter and branchier seedlings is attainable, especially at the family level. However, depending on the objective of selection, number of branches may be considered as an undesirable characteristic. In that case, simultaneous selection for height, diameter and less branchiness will be ineffective, but this expectation should not be emphasized until refinement of the method of assessment of branching patterns is carried out because all branches had not the same importance, depending on their size and position on the tree. '3" 37 Table 11. Phenotypic (between-family, within-family and total), genotypic and replicate correlations among growth characteristics in a black locust nursery progeny test. Between-Famil Correlations df=9 l 2 3 4 5 6 7 8 Height Height Height Height Height Diameter Number Thorn day 40 day 63 day 82 day 108 day 137 branches length 0.919 0.901 0.832 0.830 0.622 0.428 0.118 0.970 8.2%; 0.818 0.718 0.472 0.183 Within-Family Correlations gdf=1921) 1 2 3 4 5 6 7 8 Height Height Height Height Height Diameter Number Thorn day 40 day 63 day 82 day 108 day 137 branches length 0.867 0.757 0.665 0.668 0.618 0.435 0.139 0.911 0.884 0.827 0.725 .499 0.214 0.947 0. 3 0. 0. 0. 0. 8 Total Correlations (df=l930) l 2 3 4 5 6 8 Height Height Height Height Height Diameter N er Thorn day 40 day 63 day 82 day 108 day 137 branches length 0.871 0.769 0.679 0.681 0.622 0.428 0.117 0.917 0.823 0.826 0.718 0.472 0.183 0.942 0. 3 0. 0. 0. 0. 38 Table 11 (cont’d) Re licate Effects Correlations df=3 1 2 3 4 5 6 7 8 Height Height Height Height Height Diameter Number Thorn day 40 day 63 day 82 day 108 day 137 branches length 0.386 -0.044 0. 0. 0 0 O 0.943 0.964 0.960 0.961 0.911 0.988 . 8 Genetic Correlations 1 2 4 5 6 7 Height Height Height Height Height Diameter Number Thom day 40 day 63 day 82 day 108 day 137 branches length £301 0:978 6:940 0.851 . - u 1 ' ~ ' - .1.. - -1- ‘ . -. . - . - I .‘ 1,. '. - a .,l . . l . . . - . . , .. ,- .- .' .l | " -_ _ .r " . ' l‘ . ____ --- .- - . . ‘__ r - _ .--' “=1! .. . 44"“ '. 1'. _ 39 In contrast, the correlation coefficients associating thorn length with total height, diameter and number of branches followed different paths depending on the level of correlation. At the family and genetic effect levels, the correlations were negative whereas at total and within-family levels the coefficients between thorn length and height, diameter or number of branches were positive and significant (Table 11). Since thorn length is an undesirable characteristic, it appears that selection of families for tall height and large diameter based on short thorns as criterion is feasible but selection within these families will be ineffective. In summary, the relationships between growth characteristics as observed in the nursery were strong and positive except for thorn length. In addition to the moderate heritabilities obtained at family level, simultaneous selection at family level for height, diameter and thorn length appear to be reliably feasible. However, whether these favorable relationships will hold over time and in field tests has to be proven before reaching any conclusion. 2. Relationships between nursery growth characteristics, seed weight, percentage seed germination and field height performance (Table 12) 2.a. Effects of seed weight. Results from several studies have identified seed weight as a source of variation in seedling size in the nursery and field tests involving several species such as loblolly pine (Sluder, 1979; Bailan et a1., 1989), pecan (Adams and Thielges, 1979), Douglas-fir (Silen and Osterhaus, 1979), jack pine (Radscliff, 1981) and red oak (Kriebel, 1967). Since variations in growth rate resulting from Table 12. 40 Family mean correlations of seedling growth characteristics in the nursery with l-, 2- and 4-year-old field height, with percent germination and with seed weight of 10 families and in parenthesis of the 8 families of black locust after deletion of 2 unstable families from the 10. Field Height Performance Laboratory Determination Nursery Measurements 1-year-old 2-year-old 4-year-old Percent Seed germination weight Height day 40 0.227 0.211 0.063 0.188 03434 (cm) Height day 63 0.134 0.110 0.090 0.219 0.319 Height day 82 0.171 0.122 0.075 0.126 0.304 Height day 108 0.357 0.241 0.215 -0.172 0.370 Height day 137 0.346 0.230 0.215 -0.175 0.365 (0.668**) (0.715**) (0.781***) (-0.043) (0.509) Total height increment 0.360 0.226 0.240 -0.245 0.336 Diameter (mm) 0.546* 0.454 0.486 -0.133 0.722** (0.693**) (0.768***) (0.768***) (-0.167) (0.799***) Number of branches 0.498 0.495 0.462 -0.507 0.548* (count) (0.567*) (0.607*) (0.669**) (-0.451) (0.566*) Thorn length -0.211 -0.289 -0.238 -0.238 -0.599* (score) ('0.239) (-0.434) (‘0.249) ('0.124) ('0.639**) Field height performance: 1-year-old 1.000 -0.184 0.563* ('0.225) (0.571*) Z-year-old 0.905*** 1.000 -0.229 0.545* 0.949***) (-0.158) (0.594*) 4-year-old 0.906*** 0.884*** 1.000 -0.148 0.464 (0.939***) (0.955***) (-0.350) (0.516) *significant at 0.1 level **significant at 0.05 level ***significant at 0.01 level 41 differences in seed weight appears as environmental effects (Sluder, 1983) and add to inherent variation, its effects will result in decreasing the precision of juvenile selection. From this study (Table 12), family mean correlations between seed weight and nursery height at different measurement ages did not appear significant and decreased over time (0.434 to 0.365). Regression analyses between seed weight as independent variable and initial height or total height as dependent variables, indicated that 18.85% and 13.35% of the variation, respectively, in initial height and total height were related to the weight of the seed. In contrast, family mean seed weights were positively and significantly correlated with diameter (P<0.05) and number of branches (P<0.1) whereas the correlation of seed weight and thorn length was negative and significant at 0.1 level of probability. These results suggest that selection based on seed weight in the nursery will result in larger diameter, branchier, less thorny and to some degree taller families. Results suggest also that, since seed weight functions as environmental effects to mask variation in inherent vigor (Sluder 1983), previous results about heritabilities and correlations were inflated and thus less efficient in predicting later growth. On the other hand, correlation coefficients between seed weight and field heights were significant for first-year (P<0.1), second-year (P<0.1), but not significant for 4-year old seedlings (r=0.464). Regression analyses between seed weight and field heights showed that 31.80%, 29.79% and 21.57% of total variation, respectively, in l-year, 2-year and 4-year heights were explained by seed weight. These results 42 suggest that seed weight still exercised an important effect on seedling size 4 years after field planting and as a result, selection should be delayed until after seed effects have ceased. 2.b. Effects of percent seed germination. Seed germination was not correlated with any growth characteristic in the nursery and seedling size in the field. The only correlation coefficient worth notice was between seed germination and number of branches (-0.507). These low correlations between seed germination and growth characteristics (nursery and field) are indicators that seed germination is independent of growth in black locust. 2.c. Relationships between nursery seedling characteristics and field seedling size of the same families. The family mean correlations found between nursery characteristics and seedling size in the field (Table 12) were not significant and decreased among more distant age pairs. These poor correlations suggest that nursery bed selections could not be considered as reliable prediction methods. Family rank correlations between nursery and field characteristics showed similar trends as family mean correlations, indicating that family rankings were not consistent from the nursery environment to the field environment. Indeed, extreme rank order changes were observed from the nursery to the field and consisted of family 347 (poor family) moving from top level in the nursery environment to about bottom level in the field environment while family 385 (good family) had taken an inverse course. As a result, selection of the 5 top families based on nursery results would have resulted in the two types of error described by Lowe and 43 Van Buijtenten (1989) as occurring frequently in early selection, namely (1) a family with good field performance could be rejected on the basis of early test data (for example family 385), and (2) a family with good early test performance fails to perform well in later field tests (for example family 347). However, only error 1 appears to be important because genotypes are rejected before subsequent field testing whereas error 2 can be identified in the field and corrected. When both unstable families (347 and 385) were deleted from the data, the family mean correlations between nursery characteristics (except thorn length) and field seedling size (1-, 2-, 4-year) appeared significant (Figure 6) indicating that reliable selection in the nursery may be expected from those 8 families. But seed weight effects appeared also more pronounced with the 8 families precluding selection based on inherent vigor. Beyond all these considerations, there is a high level of probability that these observed relationships between nursery test and field performance may not hold since seedling sizes were altered through systematic top-pruning (at about 50 cm above ground) prior to field planting. As a result of the top-pruning, 4 families did not reach, during the entire first year in the field their size obtained from the nursery test: family 375 (-25 cm), 347 (-11.4 cm), 411 (—6.30 cm) and 383 (-0.9 cm) and naturally they become the poor families as revealed by the 4-year height measurement. Negative effects of top-pruning black locust seedlings have been demonstrated in earlier research by Meginnis (1934) who studied different regimes of top-pruning and their effects on seedling development, and concluded that seedlings should not be top- 44 L0 .OH 65 80.: co>oEmt mo___E8 H ... “mozEcE m .H in .mmm .Hmm ....mwm .mmm .Nmm .omm .mnm .mvm {Dem ”mfloncH OH .290: Bo: vco toHoEEp to 390; bonus: coming 30:20:00 .© v.50: $563600 EOE: Em: v m N H _ - IlerlIIllIIIITTITITTTTYITITIIIITIrYTIIITFIIIIII WTI'I‘YIYIIIIUII mazES 9 0I moEEE OH mo.on IIIIJ» 0 8:63 m TII AbomtchLmHoEofi I Abomtscfiggoz 66.9 ole Sod .83 .1050 T wooed 05.0 ”.850 65.0 squeIoweoo uonoleuog 45 pruned unless pruning must be done to salvage top-damaged or poorly formed seedlings. Furthermore, top-breakage of seedlings has been shown to decrease age-age correlations. Lambeth et a1. (1983) (loblolly pine) and Magnussen (1989b) (red pine), partioned age-age correlations between size and intrinsic growth rate and found that size was the major contributor component in these correlations. Sluder (1983) reported for slash pine, poor correlations between heights at age 15-year and the other ages as being due to top breakage resulting from an ice storm occurring after the 8-year measurement. Rehfeldt (1983) indicated that, to obtain reliable data for age-age correlations, progeny comparisons or family evaluations, trees with broken tops at any age should be purged from data. DISCUSSION AND CONCLUSION The variation patterns in height, diameter, number of branches and thorn length, as observed in the nursery, indicate large within-family variation compared to family variation; but, family heritabilities were much higher than within-family heritabilities, suggesting that substantial genetic gains can be made from both family and within-family selections. Thus, family selection followed by within-family selection is, logically, the first step for improving black locust. Similar variation patterns in growth and phenological characteristics were also demonstrated in black locust field plantings (Kennedy, 1983; Mebrahtu and Hanover, 1989) and are described by Boyle and Yeh (1987) as typical of long-lived trees, wind-pollinated, predominantly outcrossing and widely distributed. 46 As also indicated by the nursery results, the additive genetic variation and the estimation of heritabilities were much higher for diameter than for height, suggesting that selection based on diameter in the nursery would be more effective than selection based on height. However, the family diameter differences (P<0.05) were attributed to seed weight effects since significant relationships were observed between diameter and seed weight (P<0.05) and not between height and seed weight. That is, selection based on diameter in nursery would merely be equivalent to selection for seed weight which masks variation in inherent vigor. On the other hand, all growth characteristics in the nursery showed significant family x block interaction indicating inconsistent response of families among blocks, though attempts were made to effectively control random environmental affects through weeding, insecticide spraying, fertilization and fencing. Apparently, the interaction effects were large enough to affect family inferences in height (P<0.1) while they were not in diameter (P<0.05) and number of branches (P<0.01). These interaction effects have presumably arisen from rabbit damage that occurred in 2 out of 4 blocks about 2 weeks after sowing, and affected in general seedlings that expanded quickly after germination, and hence, offered more nutrients. However, the rabbit attacks were apparently random with regard to families and their incidence in the experiment was minimized by purging the maimed seedlings from the data, even though many of the attacked seedlings recovered quickly and figured among the best performers in the nursery. Although family means of final height in the nursery ranged from 99 cm to 128.87 cm with 114.3 cm and 110.68 cm, respectively, for good 47 and poor families, the ANOVA detected weak differences in height (P<0.1) and none for good versus poor families. On the other hand there were poor correlations between nursery growth characteristics of the 10 tested families and 4-year field height of the same 10 families, although the 5 top—ranking families included 4 out of 5 good families. The poor correlations appeared to be caused mainly by extreme rank order changes involving 2 families (1 good and 1 poor family) from the nursery environment to the field environment, since good relationships (P<0.05) between nursery growth characteristics and 4-year field height followed when the 2 unstable families were removed from the data (Figure 6). However, nursery bed selection on the basis of the 8 remaining families would result on the rejection of a confirmed good family in the field (family 385 which is the 3rd best family considering the 4-year field height). Furthermore, the good correlations obtained with the 8 families were apparently a reflection of seed weight effects since the relationships between seed weight and 4-year field height appeared also significant (P<0.05) and consequently selection based on the 8 families should not be appraised upon removal of the seed weight effect. The poor correlations between nursery growth characteristics and field height could be attributed to: (1) genetic differences arising from the two different environments (LaFarge 1975); (2) sampling variation since nursery and field measurements were not made on the same progenies (Sluder 1983); and most important (3) the top-pruning of seedlings prior to field planting. Top-pruning of seedlings at about 50 cm above ground is a current practice in black locust to facilitate seedling handling by machine planters, thus reducing planting costs and 48 also to increase survival. However, there is considerable evidence that top-breakage of seedlings would alter the relationships of nursery growth with later growth ages. Therefore, whole seedlings would be preferred to top-pruned seedlings for establishing plantations. To take advantage of all the nursery growth and still use machine planters, it would make sense to investigate the best date of seed sowing in the nursery that would yield seedlings of about 50-70 cm at the end of the growing season. SECTION III. VARIATION IN SEEDLING QUALITY FACTORS AND INSECT DAMAGE IN A HALF-SIB NURSERY TEST OF BLACK LOCUST (Robinia pseudoacacia L.) ABSTRACT Insect incidence (aphids and twig borers) and seedling form were assessed on seedlings evaluated for growth characteristics in the nursery progeny test. Results showed no statistical differences among families and for good versus poor families, both for insect attacks and stem form. However, significant differences were detected, separately, for crooked stems (P<0.1) and for sinuous stems (P<0.05), the two components of stem form. Results also indicate that controlling insect damage in the nursery would indirectly result in significant decrease of crooked stems whereas it would have little influence on stem sinuosity which appears to be under more direct genetical control. On the other hand, weak correlations were found between nursery growth characteristics or field height and, respectively, insect injuries and stem form. INTRODUCTION Insect attacks, pathogenic agents, winter hardiness, drought resistance, tree form, etc., are very important traits to consider in a tree breeding program because they may reduce the capability to detect family differences in growth characteristics (Friedman 1983) and seriously affect wood quality. 49 Tl'MLS' ‘i-HA 's e :1.'q.-' --.. .' "um-s! -' . . .i "‘ . L 5 .- . .- - .\ ' . - " u. 'I‘ ' 'l"..'..‘"r'.-:l'. ... . n - . -q vTaLEIJ . : :01 $.' ..‘..'.- .‘-'":l(.‘-?) I H -. u : }[- .-;Hu - _ I- -- ~ ' - w r .230 . , , ,. _ ... . - "'i.""!F-fl'w II ‘I"' -I-.: I”! -- -.-. ._ - .. -' - . - ' =' : I'd . . -. , _ ‘ , -i..¢:=1:; - - Jziuin? -..JFQOETHI ngu. . . - . - . _ -:' w; tsrzu- . -. . ,. .'~. -n . _ .s-n‘eieow -;n ., -- '= .w -s- .. -- . : - - - . - - 3.23¢eid sni: -” .-1 . :2...e: . I -.- n- -- --; n. .~- ~.aw-aa {Timed Ll ileuei1es 50 In this study, insect damage and stem form were assessed on seedlings evaluated for growth characteristics in the nursery test to determine their impact on seedling development. MATERIAL AND METHODS Damage by insects as observed in the nursery was mainly due to aphids (various species) and twig borers (Edytolopha insiticiana). Aphids were noticed in early stages of seedling development and stayed in the nursery throughout the active growing season, feeding on young shoots and leaves whereas twig borers appeared around mid-August attacking branches and stems. These insects seldom killed the seedlings they attacked but their effects resulted in leader and branch breakages (twig borers) or dieback of shoots and buds (aphids), and hence, stunted and often deformed seedlings. Confronted with an unusual season of aphid proliferations in the nursery insecticide sprays were applied five times during the growing season to avoid heavy damage on seedlings; July 6 (orthene + pentac), July 16 (Maverick), August 15 (Maverick + Triton Bmsé), August 31 (Diazinon), and September 6 (Diazinon). Stem form and insect attacks were assessed through scoring procedures. For stem form, l=straight, 2=sinuous, and 3=crooked; and for insect damages, l=susceptib1e, 0=nonsusceptible. Aphid and twig borer effects were not separated since a given seedling may have been susceptible to both insect species. Data analysis for these two characteristics was done by using two units of ANOVA: (1) ANOVA on an individual-tree basis for scoring data, allowing an estimate of the within-plot variation; and (2) ANOVA on a plot mean basis using percentage data (conversion of scoring data in 51 percentages) transformed to arcsine square root percent which result in no within-plot estimation. Table 13 presents the expected mean squares for both units of ANOVA (derived from Foster 1986). Variance components and narrow sense heritabilities were calculated as well as correlations with nursery growth characteristics and field height. The means were separated by Duncan's multiple range test if the analysis of variance revealed significant differences (P=0.05) among them. Narrow sense family heritability was calculated only if there were significant differences among families (P<0.1). RESULTS AND DISCUSSION Variation in susceptibility to insect attacks and stem form The ANOVA based on scoring data (Table 14) showed no significant differences among families either for insect attacks or stem form while for both traits family by replication interactions appeared highly significant. The absence of significant family effects in insect damage was probably caused by insecticide sprays which also can explain the non—significance of family variation in stem form since insect injury to the growing points of seedlings often led to deformed seedlings. From the estimates of variance components, it appeared that the within-family variation accounted for the bulk of total variation, with 92.50% and 95%, respectively, for insect incidence and stem form while family variation accounted for little of total variation in insect incidence (0.79%) and stem form (0.36%). On the other hand, the ANOVA of percentage data (plot means) allowed a more extensive analysis of stem form which was partioned in crooked stems, sinuous stems and cumulative effects of crooked and 52 Table 13. Expected mean squares for the ANOVA based on individual—tree and plot mean basis (adapted from Foster, 1986). Expected Mean Squares Source . . df Ind1v1dual-tree Plot model model (percentage) (score) Re lications r-1 2+t 2 + 2 p Ow ORF tfox CW 2 2 (r) T+ORF+fOR . . 2 2 2 2 Fam111es (f) f-1 ow+toRF+1roF 0w 2 2 —+oRF+roF t Rep x family 2+; 2 2 (r-1)(f-1) ow a”. 0W 2 —+ORF t rf(t 1) O2 Within-plot w 02R = variance among replications 02F = variance among families Ohm = variance for replication x family interaction 02 = variance of seedlings within-family t = harmonic number of seedlings per plot . ll ‘Iulhnflfiuuh. "h frat-nu.— “ In. .0 .... J * "A ... ..1 ul . . . . .. .. .. 1 .0 u. g _ R. .H r. .r —" .L .... ... u . .. a _ .1 .i _ . . _. _. .u ! . . . . .. .. . .. . .1. ... u . . . 3 . .. . . . . _ H . . . . ... .M .n . n . . ua. . .... ... n... . ..u ... . . U U. . h n . H . a n. r .. . . . . ... .. ... . . . u I .. r I. I m r .... . J . u . I. 1.. .h . .n .... r . .. I. . a .. . . . . . . . I . .. n A . .. u. a 6.. . -- -. . .. " ... ... . . . .r 1 . . e. . .Iu - l — 53 Homes axes so cossHu:Oo mH eHneu "Hake Hon.navonnw.o «omH HnH.Nova¢H.o I- HmeH.o nNoH HOHmnanqu muoHueuHHmou AHo.HVHnHo.o aamm.H mmom.H AN “an.nv¢mnoo.o camN.N HHH¢.o 5N N hHHEem moHHHEeu .1 us I- H I- us I- H noon .m> noon Hwn.ovw«Noo.o naom.H «on.H o Ao~.ov¢NHoo.o mcmn.H mno.o a nOHHHEem Hue.uvano.o i;om«~.n Hno¢.o m An¢.mvmnoo.o aan.n uno.N m usoHueoHHmom eoceHue> _ nmouum m: up woceHue> vacuum _ m: _ um scHueHuu> Show Beam cosmnHocH poomeH we cousom Honoumv even many HeSUH>HvGH .ummu hemmoum hummus: unsooH xomHn m :H Euow Emum use wococHocH uoomcH mo moumEHumm quHHnmuHuon >HHEdw use mHmmsuceumm sH GOHumHue> Hmuo» unmouwm .mucmcomsoo mocmHum> .mmumsmm new: .VH anmH ...... —.l. .. I . . .. a . . . . . . .. . . . . . .. .qu .. . _ .. . . . . . I. . r no. u I I. . . . . H . . . u. . III .II . — I - ll . _ . . a H r . . .11 ..fi- . . . — EC. .... —. I II. Ill-I. .II I.I- l I 54 Hw>aH no.0 ea equOHuHsmHu.. Hm>wH Ho.o ea peoOHuchHm¢.. Hm>oH H.o an uuuuHuHawHw. muesvw sews n ma useoHuHfimHm no: n ma A .55 >uHHHn neuHuwn II onn.o eHn.o II hHHEem ANm.Hov Ano.nmv AN¢.¢nv Ana.nnv NH.om I- wNH.om on.oN I- on.mu so.nn I- am.nn mN.n¢ u- :mN.ne Houum I- I- as I- I- m: II I: m: I: I- a: “com Hmn.mv Hn~.HNV Aoq.qu Ho.oHV .m> scam ow.¢ onH.o nn.wc «5.0 mao.o asum.mo Hn.m NHno.o «mm.mn Hm.n NMH.o an.qn moHHHEdm HHo.mNV How.NHv HNH.HmV ANn.¢nv msoHu scum wz uHue> scum m2 -Hum> noum m: -Hue> scum m2 Euou Moon Heu0H macaw msosch mamum uwxoouo ooflovHofiH voomnH sOHueHHe> no muusom Hummuswouomv ease new: nch H.e.u:ooc «H mHan “II . .-." ---.- -.-—-—- .......::..R. 3 ans-... 55 sinuous form (total poor form). The ANOVA of percent data was consistent with that of scoring data showing no significant differences among genotypes for insect injury and total poor form. However, significant family differences were observed for stem sinuosity (P<0.05) and to lesser extent for crookedness of stems (P<0.1). Family variation accounted for about 22% and 14%, respectively, for sinuous and crooked stems whereas their respective coefficients of family mean heritability were about the same magnitude (0.570 and 0.514). Family means from the percentage data are presented in Table 15 and illustrated in Figure 7. The level of susceptibility to insect injury per family ranged from 10.66% to 26.83% around the overall mean of 18.84%. Of the 10 families, 5 performed below the overall mean (3 good families and 2 poor families) and among them 4 families were the best performers in height and diameter in the nursery but the other less susceptible family to insect damage (383) was the worst performer in growth during the entire nursery experiment. That is, the best performers in growth in the nursery were not necessarily the least susceptible to insect damage, as evidenced also by the absence of significant rank correlation between total height and insect incidence. For stem form, the range of family means was as follows: 10.21 to 31.10%, 7.05 to 20.62% and 25.86 to 43.89%, respectively for crooked stems, sinuous stems and total poor form. As observed for insect injury, there was also no consistency between performance in growth and stem form. On the other hand, there were no significant differences in either ANOVA unit between the good and poor families. _ -I . . . . . . \-.'.r '- _::_,n-- " H I. i- “: I' I .I' c I . pl IT I 'HI‘ .2“ .- ' zsehi e ' a: 5:111:33 ghoul '1 Im.: *urz.?in3ia - H ..Hw? G3 has I. =! nu;n”nna: _- ; :‘r:. FED}! £111.; Iv'J: --.. 1.1 'k'..i'n_' - n - -i: .vuuLni rnvi meie .- .. ' ..I, I'} r--'J i IVOHA 56 érimmmfiwm.mnmN¢mnmflzEo Loom MFmm.mmm.mmm.owm.w¢mnm0=Eh: U000 .63 500.5 5302 x005 ©8330 >_m>_m:3:_ :0 E ES”, oxczvmwm 96 85203 385 R 8:05 :Eo... nvm 5m, mm, W mam mm % W W W / /$ W. W: W... W... .... ro¢ mooEov yommE ELE Loom :59 E -8 Emgm @9380 g Em? 903% RE ow ebmuewed .Auwon ownon wamapaaa u.:uoqbnv no.0 an ucoofiuaamau haauoaumfluauu non mun umauomnsm csdm 0:» Ana: mamas assaoo a casuaz 57 No.wn an.ca om.HN em.mfi Nan.a .mwa.o moaawedu aH< no.mm n¢.na no.NN oo.mH Ham.a oma.o moaadauu Room oa.nm me.ma NB.HN mo.oH nun.a noa.o mowaaeuu vooo ow.nN new ono.n «on Hm.oa new oo.oH nqn o¢.a hem oa.o new OH Nm.m~ Ham enme.o «on «N.na oom o¢.oa own an.a Hon mHH.o own a an.cm Non onaao.aa nun oq.om m¢n Hm.na wcm nn.a own mna.o men a Ha.om mom onoo¢.ma mam «w.HN mom on.oH new nn.a men onH.o mom 5 mm.om 0cm onaon.en non 0N.NN Ham Hm.na Han nn.a mom nna.o Hon m om.nm non nunn.nH new mn.NN nmm hm.mfi HH: oo.H Non n¢H.o Ha: n no.5m own nuan.oa w¢m wo.NN mmm ow.a~ w¢m Hw.H nan nHN.o mom e no.a¢ mam umm.ma Hae on.¢~ Ha: mo.¢~ non co.H mom meN.o mam m NN.N¢ nun omm.oa can mo.om Nam nN.nN Nam om.H Ha: mnN.o «on N mm.m¢ a”: uNo.ou own oa.am nun mm.o~ mum en.H nun oom.o nun H ooaovaonH snot haaaam ado: haaaam anon uoom Hopoa unauosndw mumGonoouo noounH Show swam ooaoufioaH poouaH undo ownpaoouom dado wnHuOom .mmHHHamm umfiooa xoman vmumafiaaom-como 0H How hummusc msu CH mwcchmu m>wumHmH vcm anew Emum USN moaovwoaw uommcw cmmz .mH mHQmH I‘m-w. .. ”warn-...: 5.4:. ...u m. “.....Iqu... mm. a... ...—v." . T u I I I .- :5 I. .. I. I .I . . . I .. . . I. . I .. I .. .. . I J 1 .I I.... II. . I I . I I v. -1. II - . . .. II I I I . . . ...... I _ . .. . I ...». .I .. I II . . n _ . . I III . II I II I I I I I I I I I I I III ...I I I 58 Relationships between insect injury and stem form The correlation matrix between insect damage and the components of stem form is shown in Table 16. As anticipated, positive and strong correlations were observed between insect damage and crooked seedlings since the injuries caused by insects to the growing points of seedlings appeared to be a major causative agent of stem crookedness. However, correlations between insect damage and total poor form were positive but not significant at family level while correlations between insect damage and stem sinuosity were negative but not significant (Figure 8). Regression analyses between insect damage (independent variable) and stem form components (dependent variables) showed that 64%, 32% and 18% of total variation, respectively, in crookedness, total poor form and sinuosity of stems were explained by insect injury. These results suggest that controlling insect damage would indirectly result in a significant decrease of crooked stems whereas it would have little influence on sinuosity of stems. Thus, stem sinuosity appears to be under direct genetical control and is apparently caused by physiological mechanisms related to cambial activity (Franklin and Callaham, 1970). On the other hand, while crooked and sinuous stems were not correlated at family level, total poor form (crookedness plus sinuosity) revealed significantly related to stem crookedness but not to stem sinuosity. Regression analyses indicated that about 56% of family variation in total poor form was explained by crookedness versus only :1-. unified 1| I'l:I :"J 7- ‘ -I I '- n I.- t '2 '_|. 1': h' - ' “ML? 'I i ‘In'a "-"q'.'I’I 59 Hw>oa Hoo.o nu unaowufiamfimIII Hm>oa Ho.o pa unuofluanwauII Ho>oa no.0 pa unuosudawsuw cmn.o sanwe.o nao.o omH.o NoN.o moo.o wo~.o wan.o mno.ou mcmN.o ncN.o No~.o nuwBoH shone an.ou :HNc.o chen.ou Noa.ou moo.ou nom.ou noo.ou «m¢n.o mn¢.ou HHo.oI Itome.o nan.ou mononoun No.02 mHo.o Ham.o won.ou Nca.ou moo.on cNN.on ono.o :eqn.o aoc.on woo.o INmm.o onn.ou Houoaufln nHH.on mNo.o onn.ou mao.ou omo.ou mHH.ou ono.ou noa.o Non.ou Neo.ou mNN.o omn.ou unwaon annoy "Amnuoe uoamv mow nunauopouuano 5930“» hummusz anon ooo.a ooo.H ooo.a noon Huuoa cnm.o an.o oo¢.o ooo.a ooo.H ooo.H haemoaawm ccaocn.o s:¢omn.o geno.o cinmm.ou ccnmc.ou nmm.on ooo.H ooo.a ooo.H muonooxoouo ooaooaonu cwccon.o «swoon.o oae.o Iccae.on acanc.ou omm.on «simom.o ¢IINo0.o «toow.o coo.H ooo.a ooo.H noomcH Aonluuv Aomnuov “onluov Aomuuuv Aaounoa noluvv Rampaoa Amluov “Hupaoa Aoluvv Aaouaoau Aauuov Aamuuvv noua>aov AAHauu Ammuuov Icoua>60v hHfiauu Ammluvv unoua>aov haaauu Aamuuvv noufl>aov haaadu Houoa uouum Gooxaom annoy Houum Gooxpom annoy uouum cooxuom Hauoa uouum cookuom anon owouaoouom anon Room annoy hpaaosndm anonvoxoouo cocooaoGH noonaH .ummu %Gomoum hummusc umsooa xomaa m CH mowumwuouomumso SuBOHw hummuda £uw3 Show Eoum tam owmfimo uoomcw wcwumHoommm mucmwowmmmoo Cowumaouuoo tam .mufiocoaaoo show Scum cam owmamo uoomaw Gom3umn xwuuma CowumHoHHoo .wH canoe .53 \Eooota 2402 x003 85:30 30223,: co E BoomE 3 p.832 meEoom €5.88 0 826 53 35603 to :58 80% Leon N 00896 to 20:20:00 .w 230: omoEoo boomE Emotoq 60 mm NN _ 0N @— p w— 3 p L N. O— 4 mEBm omxooto mEBm m30:c_m Etoe Loom :53 Q IOP 1: Im— INN row Ion 4n Imm INv rev om LUJO} JOOd wowed . .. .. .- . I . ..J... —l— 61 7.50% explained by sinuosity of stems. Therefore, crookedness could be considered as the dominant factor contributing in total poor form. Relationships of insect damage and stem form with nursery growth characteristics and field height (Table 16). Negative and non-significant correlations were found between total height, diameter, number of branches with, respectively, insect injury and stem form components in the nursery test. In contrast, Genys and Harman (1990) reported first-year height and diameter of 25 populations of black locust in the nursery to be positively and significantly correlated to injury by twig borer. On the other hand, no significant associations were detected for the same families between first-year and fourth-year field height and insect injury (-0.300 and -0.22, respectively), total poor form (-0.339 and -0.083, respectively), crookedness (-0.402 and -0.191, respectively) and sinuosity (0.060 and 0.126, respectively) as evaluated in the nursery. Mebrahtu and Hanover (1989) found from over 400 families of black locust, including the 10 families studied in the nursery, a much lower and positive correlation between first-year field height and injury by twig borer (r=0.073). CONCLUSION Insect damage and stem form did not appear as a potential tool for nursery selections as evidenced by their non-significant variation among families (probably due to insecticide sprays) and their weak correlations with growth characteristics in the nursery and in the field. However, injury by insects appeared to be a major causative factor of stem crookedness whereas it showed little influence on stem :‘ . ' _ _ .,_; I, s. - :ra- - : '_ ' _"I I _- I l-"_ I. '_l hill ,r‘dgi‘sfl -v . ' .. .u my??? bma , .3 ‘J;' r '-r_-‘sxi :13:o;2. :0ERI) usmrsfl . . _ I 1: . 9 '- n .' so? iv-sid lo 'I .1" _n: ' ' "'-.-.c-.IZ=»1'.L-'-u .- , . . ' - ' _j .. "I _u'I " ‘ _ f 1’ 1 "5! ..-rl: .I .JI‘..J' .3 .0 ' 'b '( I.) ‘ -\-'_' '.Iu . . ). '..’..- ' ';'.I(‘- his . ' e - - s n ( -) .l :I u" - ' -i - J .xsqa-n ' - 9...: n ' . . I"- :1} I ' . ' u.i'-..- . ' “HP: ‘1 E!‘ . .' ' I= I ."::'1:u‘ . ~' . -. . I z: Jr‘Igi'ar: ‘I.TE‘.L_.'NZOn I I. - .‘, '- '.- I; '. ”II-"I1 ' . - :i-I. . * ”MI-'32 V:'1-‘.'.‘.L’fi - 1' . - i :-.-:.--.._\ng) Miriam} - ‘ .I _' ' ..'".' '- .. - --.=;: '.: m I . . .. -. -- .' -.--.='-'.= {-2 t -..' rri ass-40H. ' “. -,.. :'- " -. ' -'. mm. ' .-; ' ' " "I.I'II'. it) 62 sinuosity which apparently was caused by lack of apical dominance, and thus, was under more direct genetical control than crookedness. Since the stem borer (Megacyllene robiniae), the major threat of black locust field plantings seldom occurs in the nursery, identifying genotypes resistant to insect damage in the nursery does not necessarily mean that these genotypes will be resistant to the stem borer in the field. Therefore, breeding for insect resistance in black locust should be done on field plantings while nursery insects should be strictly controlled to improve the form of seedlings. SECTION IV. EFFECTS OF GENOTYPES AND GROWTH POTENTIAL ON GAS EXCHANGE CHARACTERISTICS OF BLACK LOCUST (Robinia pseudoacacia L.) ABSTRACT In this study, variation in late season photosynthetic efficiency and its relationships with seedling growth characteristics were investigated from the nursery progeny test. Mean net Pn per family ranged from 10.96 [anol m‘zs'1 to 13.42 umol m’zs'1 but no statistical differences among families or between good versus poor families were found. Family differences accounted for little of total variation (2.88%) while most of the variation was contributed by the within-family variation (66.40%). On the other hand, poor and inconsistent correlations were found associating late season net Pn with growth characteristics suggesting that late season net Pn is not a potential tool for nursery bed selection. INTRODUCTION Physiological and nutritional characteristics (photosynthetic rates, uptake and use of nutrients,) are related to genetic potential of tree growth (Bailan et a1., 1989) and thus, theoretically, can be used as a tool to improve progeny testing. Genetic variability in photosynthesis (Pn) has been demonstrated in several studies involving Scotch pine (Gatherum, 1964), Douglas-fir (Luukanen and Kozlowski, 1972; Campbell and Rediske, 1965), larch species (Ledig and Botkin, 1974), aspen (Gatherum, et a1 1967; Foote and 63 -I‘ . I -I , \‘ I _ ' 'II I " ' I l I l . I. I I I . . . " '. _, , II . J' I i. I I _ -_ '5' I I f ' I“; I 5‘ ... I . "- I41”. |r a: '-| QJI'fl lql I. 1]— V . - ‘ =-r.'.I. J .. ' - ' I - ‘, _I 'II II . I ". .IrI .1." ": JuiT'dI-IA 53:15. In; .‘ 5m“: ' -' - 1:; - ..mIrI'T 5:}; "1' - '31: ' I'I .- - 3.5-. '1: I Hut! .‘ I--1 ; "I. f-.' n". n- .I' II. n l- ' \I .I I". I I'. -'= Luci-«r. n} :. 'I'II'.J.|- ‘: 64 Schaedle, 1978), black walnut (Carpenter, 1972, 1974), sycamore (Ledig and Botkin, 1974), black locust (Mebrahtu, 1989), etc. These studies were either dealing with Pn efficiency (COz uptake per unit leaf surface area per unit time) or Pn capacity of an entire plant (002 absorbed per plant per unit time), both being a determination of net Pn, i.e., gross Pn minus rate of respiration. These studies have shown the weakness of using photosynthetic measurements (either in natural conditions or in controlled environment) as a tool for predicting present and future growth since results were not coherently correlated with growth characteristics and productivity. Indeed, correlations were either weak or strong, positive or negative, inconsistent over environments and time. These incoherent relationships are interpreted as primarily caused by failure to account for seasonal pattern changes of assimilation (Ledig and Perry, 1969; Boltz et a1., 1989). Considering this assertion, the objectives of this study were to investigate the potential of Pn efficiency as a tool for nursery bed selections through Pn measurements taken in natural conditions and at different times on the 10 families evaluated for growth characteristics in the nursery. However, this present study is of limited value because, out of three scheduled measurements, only one has been performed (due to technical reasons) and coincided to the late season growth; but it is of interest to investigate the variation in late season net Pn and determine its relationships with seedling growth characteristics. MATERIAL AND METHODS To conduct the experiment, 5 healthy seedlings from those measured for growth characteristics in the nursery were randomly selected in each .l' .-" _: ' '-. . . ' I. - \"': . _"IA. :1"; 5:515 ._ ‘ ' _ ' _ ' -.'1 ."'?”.u' ,nlfljoa .. . ' - I a IIILI .ndJlE 919v .I:-:: '.‘.r:.-.-.:: 1.1 1 5:51: \ Inns . ' - '='.-'.".Ii«_r gulnu ., 11') ..-' _l-I'L . r .. - 4, .I --. - . =- ..." . Ara-In"; ’_ ‘ ' :I : IL I: -.ln.-ll:-'J - - . ' _ " .Jr .I. -'o "I J'I .. I ‘J .- 7 ~' i'!..’ I ‘ I“ :5 ' _I ‘ " - 4"" v (I - '-'_- s I, r.” .- . . !. - _ _, .- !-._'ir_'.-I:I'".q ._ J ._ . - ;. . _;I'.' ..-:!= is“! TI"! --!.: "fl OI 2w}: ' '. -- . .""uio¥{ . - - . I - - I . -- -. - .I-I: I‘IIIiI-an'laa '.-' ::...‘-' . - - .' I' - - 3:”: l'!!|.'-?!‘I'J“ .~. I . I , _ :' --"-._'_-‘ I‘ar-‘I'I'I‘i 0;! _- . . . , =-. . .- = .=' '. '|"1L 1 H19": ’ ‘- .-I‘. '-.-1.'I .-'.-“.I:I'51"I'AV ' 1 .I ' ' I " - '.- . .. - 65 plot, giving 20 seedlings per family (200 seedlings total). For the selected seedlings, about 7 leaflets from attached leaves of the same degree of development and well exposed to natural light were sampled and their leaf surface area determined by using a LI-3000 area meter (LI- COR, Inc.) prior to Pn measurements. Then net Pn measurements were made during natural light period with a LI-6200 (LI-COR, Inc.) portable porometer comprising a sample chamber. Due to unfavorable weather conditions (clouds, rain) measurements had been taken during four non-consecutive days (September 20, 24, 25 and 27) with a block (replication) per day, i.e., 50 seedlings per day. Each day of measurement began when direct sun had covered the nursery site and dew had evaporated from the seedlings (9:30 - 10:00 a.m.) and finished when the sun began to leave the site (4:30 - 5:00 p.m.). There were some differences in measurement conditions among blocks (light intensity, ambient C02, ambient temperature, relative humidity and rate of air flow), but these conditions were rather uniform within each block. In addition to the measurement of Pn efficiency, stomatal conductance (Cs) and transpiration rates were obtained from the data. Analysis of variance on the basis of individual-tree data were performed on Pn efficiency, stomatal conductance and transpiration, and their subsequent relationships with nursery growth characteristics were calculated and analyzed. :1: l']-‘ .'1 _ I -l'.' I. I I .8I.- h: gnjvzg ‘s: 'fiiuuo I -. '- -. 1|.“an .J rIfifi had ' .- Eh”: Rib due}! I JJia .1.-I'? MN I I. i‘ I. 'Ilw «' *u-Inl '3 14']: 1d .ionfd . p, - .-:I".'Iu'1‘.'1r‘u LlflyIud§ :I.uysedr2 v-’.!na[au 66 RESULTS AND DISCUSSION Variation There were no significant differences among families or between good versus poor families at 0.05 level of probability for net photosynthesis (net Pn), stomatal conductance (Gs) and transpiration, all measured during late season growth (Table 17). However, family differences were detected at P<0.l for stomatal conductance. As expected, because of the variability in measurement conditions among blocks, significant differences observed for the family by block interaction overshadowed inherent family differences. The significance of the interaction was stronger for Gs and transpiration (P<0.01) than for net Pn (P<0.05). Family differences accounted for little of total variation in net Pn (2.88%) and stomatal conductance (6.20%) and none in transpiration rates while most of the variation was contributed by the within-family variation with 66.40%, 72.88% and 66.93% of total variation, respectively, for net Pn, Cs and transpiration (Table 16). Mean net Pn per family ranged from 10.96 umol m”%f1 to 13.42 umol rigsfl'or 89.842 to 109.95% of the study mean with only 5 families performing above the overall mean (Table 18). The 5 best performers averaged about 6% better than the study mean, and among them only one family (382) figured in the 5 top families for final height and diameter in the nursery, indicating a reversal tendency of the order of family ranks between late season Pu and total height and diameter in the nursery. Further, only 3 families out of the 5 best for net Pu and residual growth were common to both and the worst performer in net Pn (family 375) accounted for the 3rd best in the late season growth. F7 .l “Jr I'l.‘-' 3“th . ; . - : Ln‘uzzam II: .-.I :.nu3351113 r .d .hfisasqxa 1. ‘E r13. '_I .' “'.Jdold r II L ' ' '-I‘. tram} s" . 3i _. _ . “':.1 at, “ :un :01 --O. 1 _'I I-- '. “55-1 “"'“ '5'! 3’ L-‘fl.§) n J - -" asJ?J u | I ' '.Iflq“53 II'I 1'" . ' - a "a"m -_I ...- Anim- $1?qu , I'VE. ’- "EH5 It'll-'3 -_ _'.IL11:_': .' ' p a=nfl 1613 67 npnannunoum no Ho>aa n0.0 an paaonuaannu II suflaanonoum no HI>IH 0.0 an uuaofiunamna I nouaaaau noon Imm noaaaauu coon Imw “ H ”000.00 A00.~0 “000.00 I A500 panama snn.0 IIa~.H 0a0.0 0000.H 000~.H h0~k.HInIH0.0 00Hn.0+H000.H cocoon onus “an.0H0 “an.000 A00.00 . I II00.n IInn.~ 0H.H ~n0a00.0 nnH¢00.0 n0000.0-~n000.0 00H00.0+H.00.0 nonuouflnfluaaua _ A00.00 “no.040 “00.00 I ooaouosuaoo II00.0 II~0.~ Ik0.H anke.0 0-n.0 n0n0.0-0n00.0 00H.0+000.0 Hannaaun “00.000 .0k.00 A00.~0 . I moaofionuuo II00.0H IH0.H In.H 0n-.~H 000H.NH 00.00-00.0H n0.0+0~.~a osaonpasaouoam Acondwuc> NV Aoondauo> av uuouIm uaooIm Aooaunun> "0 soduoonanom soduoouoanH nuopnm haaaum mm mu owqum ado: mudguauopoouono “I! I J .ummu hfiomoua hummudfi m GH uswamn common mumH tam .Gowumuwmmamuu .oocmuUSUcOo Hmumaoum .mwmmfiufikmouonm Doc common muMH mom undooa xomHQ mo meHHamm UmumawaaomIcmmo 0H CH <>oz< mo %umaadm x mammz .NH manna III". I I.I-I.I I a ... . .. . I. I _ . . III 4' . III I . J. u . . 68 nI cmma ¢@H.H woaqoo.o mnwmq.o moom.wa Ham- Hm>o «Hw.o qu No.5m mummoo.o mqm om.mn oom¢m.o qu ¢w.mw o¢.oa mum 0H «oo.o AH: mm.mw commoo.o wdm qw.Hm Nme¢.o mom mm.wm om.HH n¢m m mmm.o mom Hm.om mommoo.o Haq oa.mm mm¢o¢.o m¢m Nw.wm Hm.HH Hmm w N¢H.H Ham Hm.nm oaoqoo.o Ham mm.¢m Haon¢.o own m¢.m¢ ow.HH can u mmN.H 0mm No.HoH mmaqoo.o mom qa.¢m mm¢w¢.o mum wo.m¢ mm.HH wqm o ooN.H wqm Hm.moH Oquoo.o owm ma.mm mn¢m¢.o «mm mo.ooa wN.NH Nwm m oo~.H mmm Hm.m0H mmmqoo.c Nwm Hm.mm mmmm¢.o Haq Ho.HoH mm.NH mom q Noq.a mum Hw.moa mc~¢oo.o mum mm.¢oa omomm.o Ham ¢o.woa mH.ma mwm m Nm¢.H Nwm wH.¢oH ommqoo.o mwm mm.¢0a wmo¢m.o mwm oo.moa mm.ma Hac N omn.a mwm Hm.mHH mmoqoo.o mwm N¢.OmH mmomw.o mwm mm.moa N¢.ma mwm H Emma cmma came HHmHm>o Hamum>o Hamum>o cam: zgm N cums zo mo unmoumm cam came hawamm .mH oHan 69 Therefore, an inconsistent relationship seemed to exist between late season net Pn and growth characteristics as observed in the nursery. For stomatal conductance, only 3 families performed above the overall mean whereas for transpiration 6 families were found above the study mean. Correlations Relationships between physiological characteristics (Table 19). The correlation coefficients at family level between late season net Pn and stomatal conductance (r-0.623) and/or transpiration (r=0.464) were not significant but moderate while Cs and transpiration appeared strongly related (r=0.813). These results indicate that high stomatal conductance in late season growth would lead to increased rates of transpiration (i.e., loss of water) but not necessarily in high photosynthetic rates. On the other hand, total (individual-tree) and within-family correlations among the three characteristics were all highly significant (P<0.01) suggesting that mass selection (i.e., selection of individuals regardless of families) and within-family selection based on late season Pn efficiency would result in discriminating seedlings with higher Gs and transpiration rates. Relationships between Pn efficiency and nurserz growth characteristics and field height. Negative family correlations were found associating late season Pn efficiency with initial height, total height, diameter and number of branches (Table 19) while positive and weak correlations were observed between Pn efficiency and late season growth, thorn length, stem form “H 7O Aeoscflucoo as manage ooo.H ooo.H ooo.H coflumunmwamgs mocmuodwcoo ¥*¥¢Hn.o «*maw.o ¥**own.o ooo.H ooo.H ooo.H Houmaoum %**on¢.o ¢o¢.o %**omd.o ssrwoq.o mmo.o %¥*wNQ.o ooo.H ooo.H ooo.H mwmonuckmouonm owalmp mumc owauwp mumv mwanmv mump Nassau sauamm moanmu sausmm Nassau mmsumu sauamm aspen“- mmaumu -cfifluws -Goo3uom HmuOH -GHSuHB -Goozuom HNUOH -fiafluws CooBumm HNuOH coaumufimwamuH mucouoducoo Houmaoum mflmonuchmouonm .wowumHhmuowhmflu NQUHMOHOHmKJQ madam .MEOHHNHGHHOU kHflafiwluwfluwh tum KHHEmwnuuukuun Munch .unwfiws UHoHM paw mofiumwhouomumfio Luzoum %Homudfi 6cm mowumwuouomkmno HmowwoaomeLQ Coosuofi muowumaouuoo .®H oHQQH rt“ Hm>mH Hoo.o um unmanneawnm*** Hm>mH Ho.o um ucmofimwcwfim** Hm>mH mo.o um unmouuucwums Aomm.ov Noa.o pawn»: “mus-5uusom Amoo.o-v oom.o Amoa.ov HNN.o Amwa.ov NNNO.o usmum: g8&388 Amwo.ov swo.o Ammo.ov oNN.o Asmo.o-v ammo.o- unmomn Haws-umufim Amm~.o-v Hmo.o- Asma.o-v Nmmo.o uuwmmm Asma.o-v oma.o- uswfimz comm AHmH.o-v wmm.o- Awso.o-v qHH.o- AmoH.o-v «NH.o- coflumaflauwm unmoumm AooN.o-v so~.o- Asmo.ov QOH.o- ”mwm ANHN.o-V ¢m¢.o Amo.o-c son.o Aswm.o-v moN.o Aouoomv ago“ amum Aswm.o-v oam.o Asmm.o-v Nos.o Aoom.o-v sma.o Amuoomv mmmamc uoomcH Awfio.ov mmm.o Amms.ov mNH.o AsNo.ov ¢w¢.o Amuoomv ruwcmfl agony A¢NN.o-v moa.o- A¢NN.o-v «No.0- AmHm.o-v mH¢.o- monosmun we .oz AomN.o-v wmq.o- AHNm.o-v mH¢.o- Ammm.o-v mmm.o- “mumamoa oom.o mm¢.o wNH.o nusoum usmnmn Hancomwm Aswo.o-v Hmm.o- Ammm.o-v *Nmm.o- Aooo.o-v Nam.o- unwfiwn Hmuoa Imoo.o- ammo.o- iswaw.o- urmoma HmuuucH ”mmmmmmm :oHudnammcaHH oucuuufivcoo Adamsouw mHmoSuahmouOSm mafiumauouomumno .mu:%woa VHQHN wad mowumwhouomhmao khme3fi aqua mowumwhouomhwco HNOMMOHOMmknm muwumHoommm «mwmocu:UHmQ cw» anewummohhoo «sou paw anewuwwohhoo sues kmwfiflk Av.uaoov ma mHQMH 'H rxu 72 and insect damage in the nursery. Similar trends of correlations were also observed between nursery growth characteristics with stomatal conductance and transpiration (Table 19). Finally, little association was found between late season Pn efficiency in the nursery and seed weight, percent seed germination, and l-, 2— and 4-year field height. These poor and inconsistent correlations relating late season Pn efficiency and growth characteristics compare in many respects with other studies on photosynthesis (see Introduction) and are mainly caused by the failure to take into account the seasonal changes in photosynthesis. For example, Logan (1971) found in studying a 7-year old jack pine provenance test (Pinus banksiana Lamb.) a favorable relationship between photosynthetic rate and tree height in October and not the other months. Therefore, photosynthetic rates cannot be characterized by measurements at only one period in the growing season (Ledig and Perry, 1969). CONCLUSION This study based on late season Pn efficiency has shown: (1) no statistical differences in late season net Pn among genotypes of black locust grown in the nursery; and (2) inconsistent relationships with growth characteristics. It appeared that photosynthesis is a complex characteristic greatly affected by plant architecture and seasonal changes, and thus cannot be characterized by irregular measurements. However, genetic improvement may result from comprehensive studies of Pn, if in addition other factors such as relation of Pn to respiration and distribution of 73 photosynthate within trees are taken into consideration (Luukkanen and Kozlowski, 1972). F '5! REFERENCES WA REFERENCES Adams, J.C., and B.A. Thielges. 1979. Seed size effects on first— and second-year pecan and hybrid pecan growth. Tree Planters' Notes pp. 31-33. Bailan, Li, S.E. McKeand, and H.L. Allen. 1989. Early selection of loblolly pine families based on seedling shoot elongation characters. Proc. 20th Southern Forest Tree Improv. Conf. pp. 228-234. Boltz, B.A., B.C. Bongarten, and R.O. Teskey. 1989. Seasonal patterns of net Pn of loblolly pine from diverse origins. Can. J. For. Res. 16:1063-1068. Boyle, T.J.B., and F.C. Yeh. 1987. Within-population genetic variation: implications for selection and breeding. Can. Tree Improv. Assoc. pp. 20-42. Burdon, R.D. 1977. Genetic correlation as a concept for studying genotype-environment interaction in forest tree breeding. Silvae Genetica 26:168-175. Campbell, R.K., and J.H. Rediske. 1965. Genetic variability of Pn efficiency and dry matter accumulation in seedling Douglas-fir. Silvae Genetica 15:65-72. Carpenter, 3.3. 1972. Variation in leaf morphology in black walnut (Juglans nigra L.) and its possible role in Pn efficiency. Proc. Eighth Central States Forest Tree Improv. Conf. pp. 24—27. Carpenter, 5.3. 1974. Black walnut in central Kentucky: growth and development of half-sib families under artificial shade. Proc. Ninth Central States Forest Tree Improv. Conf. pp. 120-130. Davis, J.M., and D.E. Keathley. 1987. Toward efficient clonal propagation of mature black locust trees using tissue culture. Nitrogen Fixing Tree Res. Rep. 5:57-58. Eisensmith, S.P. 1985. Plotit. Scientific Programming Enterprises, Haslett, MI 48840. 74 Flu 75 Ernst, S.G., G. Howe, J.W. Hanover, and D.E. Keathley. 1983. Genetic variation and gains of specific gravity and woody biomass in a jack pine half-sib progeny test in Michigan. Proc. 3rd North Central Tree Improv. Conf. pp. 111-122. Faulkner, S., and J. Toliver. 1983. Genetic variation of cones, seeds, and nursery-grown seedlings of bald cypress (Taxodium distichum (L.) Rich.) provenances. 17th Southern Forest Tree Improve. Conf. pp. 281-288. Foote, K.C., and M. Schaedle. 1978. The contribution of aspen bark photosynthesis to the energy balance of the stem. Forest Sci. 24(4):569-573. Foster, G. 1986. 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