LEBRAR'Y ”‘HES'S Michig? n State This is to certify that the thesis entitled THE INHE‘RITANCE OF SEVERAL CHARACTERISTICS IN PEPPER presented by William M. Randle has been accepted towards fulfillment of the requirements for Mas ter' 8 degree in Horticulture 141;me UMajor professor Date 5/17/79 OVERDUE FINES ARE 25¢ PER DAY PER ITEM Return to book drop to remove this checkout from your record. ilil‘i“ l). I \l'lll...‘ YI-III'\ l'...‘..!|l .I Ill" 0. I O THE INHERITANCE OF SEVERAL CHARACTERISTICS IN PEPPER By William M. Randle A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture 1979 ABSTRACT THE INHERITANCE OF SEVERAL CHARACTERISTICS IN PEPPER BY William M. Randle Studies were conducted on 19 cultivars representing four species of Capsicum.to determine the expression of dormancy in seed germination and emergence, and to investigate the inheritance of this character. Differences in dormancy were found among cultivars. Fruit age was shown to affect dormancy. Warm dry storage also affected the length of dormancy while still maintaining a high level of emergence. Data from reciprocal progeny crosses in three families of g, annuum suggested partial dominance for non-dormancy. Ratios obtained by partitioning segregating generations suggested that 3 major genes (Anggg)influenced the expression of dormancy. A (3:1)(15:l) factorial gene model best explained the observed ratios. Q’in the homozygous recessive condition was necessary for the expression of dormancy. Studies on one hundred thirty-seven cultivars of g, baccatum var. pendulum were conducted to determine low temperature emergence response and to investivate the inheritance of the trait. Significant differ- ences (5% level) were found between temperatures (10 and 13°C) and between cultivars at 13°C suggesting genetic variability at low teme perature emergence. Data from reciprocal progeny crosses generated from four families of g, baccatum var. pendulum suggested partial dominance for slow emergence at low temperatures with additive and dominance gene action playing a role in trait expression. ACKNOWLEDGMENTS The author wishes to express his sincere appreciation to Professors Shigemi Honma, M.W. Adams, Hugh Price, and Charles Cress for their guidance as this work was being conducted and for their suggestions and review in the preparation of this manuscript. ii TABLE OF CONTENTS rials. List of Tables List of Figures The Inheritance of Dormancy in Peppers Introduction Literature Review Materials and Methods Section I The effect of dry storage on the loss of dormancy Section II The effect of fruit age on the dormancy of seed of peppers Section III The genetic control of dormancy in peppers Results and Discussion Section I The effect of dry storage on the loss of dormancy Section II The effect of fruit age on the dormancy of seed of peppers Section III The genetic control of dormancy in peppers Summary and Conclusion The Inheritance of Cold Emergence in Peppers Introduction Literature Review Materials and Methods Section I Evaluating the emergence response of the pepper at low soil temperatures iii 10 IO 13 1h 17 17 22 25 37 39 hi hh hh TABLE OF CONTENTS Title Section II The genetic control of the emergence response of the pepper at low temperatures Results and Discussion Section I Evaluating the emergence response of the pepper at low soil temperatures Section II The genetic control of the emergence response of the pepper at low temperatures Summary and Conclusion List of References iv 1&9 A9 55 70 72 LIST OF TABLES Title of Table _ Page Table 1. List of dormant pepper cultivars ll Table 2. Difference (d) between reciprocal F and F2 16 means and their corresponding standard errors for expressing dormancy in three pepper families Table 3. The effect of after-ripening in pepper seeds on 18 days to 50% emergence Table A. Population size, means, standard errors, 32 parental range, and mid-parent values for the germination period in three Capsicum families Table 5. Distribution and chi-square analysis of F2 36 and backcross progenies of crosses between dor- mant and non-dormant plant types for three different pepper families. Table 6. Difference (d) between reciprocal F1 and F2 means h8 and their corresponding standard errors in four pepper families for the ability to emerge at cold soil temperatures. Table 7. Mean emergence indices, ranges, variances, and 50 standard errors for 119 cultivars of peppers as affected by low soil temperatures Table 8. Origin and performance of 137 pepper cultivars 51 at low soil temperatures Table 9. Estimation for the adequacy of using the 56 additive-dominance model for Families I, II, III, IV by Mather's A,B,C scaling test Table 10. Population size, means, standard errors, ' S9 parental range, mid-parent values and F1 devi— ation from mid-parent values in four Capsicum families for ability to emerge at low soil temperatures LIST OF TABLES Title of Table Table ll. Estimates of components of variation; environmental (E), additive (D), dominance (H), and total phenotypic (T) variances, heritability, and genetic advance for cold emergence in four pepper families vi Page 61 Title of Figure Figure Figures 2-5. Figure Figure Figure Figure Figure Figure Figure Figure l. 7. 10. ll. 12. 13. LIST OF FIGURES The effect of dormancy and after-ripening on the emergence pattern for cultivars CMV 153h, CMV, CMV Resistant 2, CMV Resistant 3, and Big Boy sown immediately after harvest The effect of fruit age on the dormancy and seedling emergence for four pepper cultivars The emergenceF frequency distributions for parents,F , and BC2 progeny from the cross Big BoyF T CMVllSBh The emergenceF frequency distribution for parents,F BCl , and 302 progeny from the cross Big FBoyl x CMV Resistant 2 The emergence frequency distributions for parents, F1, F2, B01, B02 progeny from the cross Big Boy x CMV Resistant 3 Gene model for dormancy in peppers The emergence frequency distribution for parents, F1, F2, B01, and B02 progeny from the cross 2033 x PI 260593 The emergenceF frequency distribution for parents, F 2, B01, and B02 progeny from the cross 20332 x PI 281310 The emergence FfrequencyC distribution for parents,F progeny from the cross PI 257188? 260 93 The emergenceF frequency distribution for parents,F 2, BCl, and BC progeny from the cross PI 257185 x PI 281 10 vii 23 26 28 30 3h 57 62 65 67 THE INHERITANCE OF SEVERAL CHARACTERISTICS IN PEPPER THE INHERITANCE OF DORMANCY IN PEPPERS INTRODUCTION Pepper (Capsicum) seeds have often shown variable rates in ger- mination and emergence resulting in uneven growth, poor stands, and non-uniform.maturity. Environmental factors such as poor soil, in- adequate moisture, or improper temperatures are all known causes for irregular germination and emergence. Hewever, dormancy was never considered. Seed dormancy is an established mechanism.for survival in a large number of plant species, but has not been reported in the genus Capsicum. Dormancy may be thought of as any phase in the life cycle of a plant where active growth is temporarily suspended. Active growth halted by adverse environments such as low or high temperatures, is classified as imposed dormancy or quiescence, whereas growth stopped when all conditions are favorable for growth appear to be caused by conditions within the dormant organ itself, and is said to show innate dormancy or rest. There can be relative dormancy as opposed to true dormancy. Dormant organs induced to grow under rather specific conditions, i.e. a narrow temperature range or photoperiod, are said to exhibit relative dormancy while growth which can not be in- duced under any environmental conditions is referred to as true dor— mancy. Crocker (1916) has suggested that dormancy in seeds may occur by several different mechanisms: rudimentary embryos that must mature before germination can begin, complete inhibition of water 1 2 absorption, mechanical resistance to the expansion of the embryo and seed contents by enclosing structures, encasing structures inter- ferring with oxygen absorption by the embryo and perhaps C02 elimina- tion from it, a state of dormancy in the embryo itself, and combina- tions of any of the former. Freshly harvested pepper seed was observed to exhibit an alleged dormancy resulting in a delay in time to germination. This delay alluded to an after-ripening nature of the seed; the after-ripening being the process by which dormancy is overcome. Researchers anxious to grow as many generations in as short a time period as possible need to recognize dormancy in freshly harvested seed and know the methods to overcome it. The objectives of this study were: 1. To determine if’dormancy is exhibited in pepper seeds. 2. Analyse the nature and characteristics of the dormancy. 3. Determine the genetic control of the dormancy. LITERATURE REVIEW Peppers were traditionally thought of as a non-dormant crop, their seeds known to germinate soon after extraction from ripe fruits. Studies on seeds of Solanaceous plants (peppers and tomatoes) re- vealed no indication of a dormant period (Odland, 1938). These seeds germinated equally well at all intervals after harvest with germina- tion percentages of pepper seed being 73.8, 76.7, 69.0, and 71.0 at one, four, twelve, and twenty weeks post harvest respectively. Mahideem, EEMEl: (1973) observed a case of viviparous germina- tion in chillies, showing various degrees of germination ipggipp, Lateral roots were observed on some seedlings. Location in the fruit had an effect on the precocious germination with most germinated seeds being found in the top and mid regions of the fruit. Mbreover, climatic factors seemed to be involved with the phenomena exhibited. High humidity and warm temperatures (maximum.temperature, 26.300; minimum.temperature, 17.800; relative humidity, 93%) were needed to stimulate germination. The authors summarized the results as "an indication of the non-dormant nature of chilli seeds." Lack of germination and non-uniformity in germination of pepper seeds has been attributed to a number of different causes. Storag;\\ temperature and moisture content of the seed previous to planting was shown to have an effect on the germinability of peppers (Barton, 1935). Air dried pepper seeds stored at room temperature for one, 3 h two, and three years had germination percentages of 67, 6L, and h5 respectively while seed stored at -5°C showed germination percentages of 80, 86, and 73. In addition, seeds containing 66% moisture stored at room temperature and -5OC had germination percentages of 7h, 7h, 65 and 70, 81, 81 respectively. Fruit maturity expressed as days following anthesis and degree of fruit color was observed to affect germination in peppers (Cochran, l93h). Mature green fruit thirty days post anthesis had a germination percentage of 61, while fruit hO days post anthesis with red-green fruit had 68.5% germination. Superior germination existed at 60 days post anthesis. Fruit that was dark red and shriveled had a germination percentage of 96. Gikalo (1966) demonstrated that location of the fruit on the pepper plant influenced the quality of the seed and its subsequent germination. Mainstem, first, and second order branches showed good germination while seeds from third, forth and fifth order branches had a reduced germination. Temperature has had an effect on a pepper seeds ability to germinate quickly and uniformly. Germination rate was found to in- crease as temperatures rose from 11°C to 30°C (Kotowski, 1926). A reduction in uniformity and germinability in pepper seeds due to coat bounding has been reported by Baker (l9h8). Coat bounds ngfwas a condition where pepper seeds emerged from the soil before the cotyledons and plumules could be freed from the seed coats. This condition resulted from the combined effects of the seed structure, the epigeal type of germination, and an unfavorable environment. Injury to the seedling resulted from the rapid drying of the testa 5 after emergence of the radicle and elongation of the hypocotyl, but before the cotyledons were freed. In addition, the endosperm cuticle was thought to have a slight confining effect while the arched charac- ter of the cotyledons increased the binding by the inflexible dry coat. Numerous species of plants have been found to contain substances which inhibit or delay the germination of seeds. Such inhibitors were brought about by environmental conditions, but more often by conditions within the plant itself (Evenari, l9h9). Groups of sub- stances which were found in different organs of the plant body and acted as germination inhibitors were: alkaloids, essential oils, glycosides, organic acids, pectins, tannins, and sugars. Konis (l9h7) demonstrated that among the vegetables a comparativ- ely weak inhibitor was found in the garden sorrel, bean, cucumber, maize, sweet potato and eggplant, whereas parsley, turnip-rooted parsley, beetroot, carrot, and spinach had strong inhibitors. Within peppers, the germination inhibitors were found in the fruit, fruit juice, and leaf sap. The intensity of their suppression varied de- pending on the location of the substances (Kbnis, 19Wh EWenari, 19h9). Kbnis (l9h7) showed the inhibitory effect of the leaf sap exceeded that of the fruit juice. Inhibitors isolated from the leaf sap were thermostable, water soluble, and non-specific with their degree of activity depending on the concentration of the inhibitor. Mbreover, the inhibitory action of a given plant depended, to a certain extent, on the age of the leaves as well as on the season. Since dormancy has been shown to occur in a number of different 6 ways, only dormancy as affected by the embryo will be reviewed. Delayed germination in hawthorne was the first observation of dor- mancy secured by the embryo and not the seed coat (Crocker, 1906). Freshly harvested seed failed to germinate even with the seed coats removed, under high temperature treatments, and with increased oxygen. Since that study a number of economical plants have been studied showing embryo controlled dormancy. Dormancy in Trifolium subterraneum.L. was orginally attributed to the morphological basis of hardness in seeds (Aitken, 1938). Here the development of hard seeds depended on the continuity of the suberin layer over the distal end of the malpighian cells in the testa. Quality of the hardness was controlled by the tension of the stiophiole cell walls and the toughness of the suberin. Similar results were found in other members of Leguminosae (Rees, 1911). A subsequent study by Loftus Hill (19hha) indicated that embryo dormancy concurrent with the morphological basis of hard seeds injg. subterraneum resulted in a delay in time to germination and was a varietal character influenced by the temperatures in which it was germinated. Depending on the variety, the dormant period ranged from five to twelve months at 22°C. In addition, a later study showed that lower temperatures (10°C opposed to 20°C) accelerated the after- ripening process. But as the seed matured, the speed of germination at 10°C and 20°C approached equality (Loftus Hills, l9hhb). Quinlivan (1971) later refuted Loftus Hills' results by showing that high summer temperatures were the causative agent in the subsequent breakdown of embryo dormancy; the germination inhibitors in the seed 7 were apparently susceptible to heat. Merely (1958) found higher levels of dormancy in T, subterraneum associated with varieties developed in cooler climates. Seed dormancy was shown to be highly heritable and dependent, at least in part, on the genotype of the embryo as distinct from that of the testa. The fact that dormancy was affected by environmental factors acting on the mother plant suggested a substance was produced by the plant and stored in the developing seed. With the absence of any mechanical resistance to dormancy in cereals, dormancy appeared to be a function of the embryo or those tissues immediately surrounding it (Vines, l9h7). Barley was tested for relative dormancy and duration of an after-ripening period. When very immature, the grain was able to germinate. But with progressive ripening, it entered a dormant stage through which it had to pass in order to again germinate. The loss of dormancy in oats (Azppg spp.) was illustrated in a number of different ways. Germination of freshly harvested Avena fatua seeds was increased by the breaking of the seed coat (Atwood, l9lh). He observed that the restriction of oxygen by the seed coat was a limiting factor in germination and searing them with a hot needle in- creased the percentage of germination. This was later confirmed by Johnson (1935a) who inferred that delayed germination was due to post- fertilization changes related either to tissue absorption or development. He also found that exposure to light appeared to slightly stimulate germination in the early stages of after—ripening, but was harmful to mature seeds. In addition, location of the panicle on the plant influenced the after-ripening period; secondary grains required a 8 much longer period than primary grains. Paterson (1976) found only a limited influence of storage temperature on the loss of dormancy. He indicated that a series of changes in the tissues of the seed coat resulted in an increased permeability to oxygen. Genetic control of delayed germination in oats was reported to behave as a recessive character in crosses between A, fgppg and A. sativa (Barber, 1923). This was confirmed by Johnson (1935b) and a model was proposed. The germinative potentialities of the genotypes varied with the time elapsing between harvesting and testing. He hypothesized that very shortly after harvest, only embryos with six dominant allelomorphs (AAAAAA) were germinable and as time passed, embryos with a progressively smaller number of dominant allelomorphs became germinable. Considerable overlapping was noted. Variability in germination due to after-ripening has been observed in peanut (Arachis hypggaea) (Hull, 1937). Hull observed in some peanut seeds that a rest period of at least several weeks after maturity was required before germination could occur under average field con- ditions. In addition, storage temperatures had a pronounced effect on the after—ripening process. Peanuts stored at 200C to 25°C reduced the rest requirements while at 3°C, progress of after—ripening was greatly retarded. Subsequent storage tests indicated that after- ripening may have continued beyond the germination threshold when a cold treatment was applied. Genetic control of the rest period be- havior in peanuts was reported to be multigenic. Stier (1937) reported potato seeds which exhibited delayed germination up to five months with the duration of the delayed period dependent upon seasonal differences. In addition, Simmonds (196A) 9 observed a high correlation between seed and tuber dormancy suggesting the two dormancies were under a common biochemical control. Futher investigation by Simmonds indicated that the embryo was not in a state of rest, but that the delayed germination was caused by some tissue or agency exterior to the embryo. He therefore suggested selection of dormancy operated at the tuber level and seed dormancy followed. MATERIALS AND METHODS Section 1 The effect of dry storage on the loss of dormancy Seed from nineteen cultivars representing four species (9, annuum, Q, frutescence, g, chacoense, and Q, microcarpum) were used in deter- mining and evaluating the dormancy period in peppers. Sixteen cul- tivars were obtained from Dr. Paul Smith, University of California, Davis, two from the Southern Regional Plant Introduction Station, Experiment, Georgia, and one from Shigemi Honma, Michigan State Univer- sity, East Lansing, Michigan (Table 1). To circumvent the reported seasonal and environmental effects imposed on the after-ripening character in other species (Johnson, 1935; Loftus Hills, 19hha; Merely, 1958), all material was grown in greenhouses at Michigan State University from April, 1977 to July, 1977 to obtain seed of approximately the same age and stage of de- velopment. During this period, normal cultural practices were followed. Each cultivar was selfed once before the study. All seeds were harvested by hand from fully ripe fruit approximately 55 days i 5 days after anthesis depending\Qp the cultivar. Freshly harvested seeds were air dried for A8 hours, treated with 50 Arasan Red, and stored at 2h°C : 10C until needed. To characterize the length of the dormancy period and its pro- gression, two replicates of 20 seeds from each cultivar were planted lO ll Table 1. List of dormant pepper cultivars Line Species Accession No. Origin 1 Capsicum.microcarpum PI 281398 Mexico” 2 g, chacoense PI 260h31 Bolivia* 3 Q, frutescens CMV SA—8 Columbia** h g, frutescens CMV SA-37h Peru** 5 .9. frutescens CMV SA~218 Brazil** 6 g, frutescens CMV SAPZlTA Columbia** 7 g, frutescens CMV SAP91 Brazil** 8 g, annuum CMV 971 Mexico** 9 g, annuum. CMV 972 Mexico** 10 g, annuum# CMV 153k Mexico** 11 g, annuum. CMV 1535 Mexico** 12 g, annuum. CMV 1615 Guatelamala** 13 .g, annuum. CMV Puerto Rico** 1h .9. annuum CMV Resist. l **** 15 g, annuum# CMV Resist. 2 **** 16 g, annuum# CMV Resist. 3 **** 17 C Q, frutescens CMV 2062 Brazil** 18 g, frutescens CMV 2063 Guatelmala** 19 g, annuum# Big Boy **** :Southern Regional Plant Introduction Station, Experiment, Georgia **Paul Smith, University of California, Davis Shigemi Honma, Michigan State University, East Lansing, Michigan Used in genetic study 12 at 7 day intervals for a period of 56 days. The first planting was sown between July 31, 1977 and August 12, 1977 (the actual day was dependent on the harvest date of each cultivar) and placed in two temperature controlled chambers-one replicate per chamber. Tempera- tures were held at 22.500 : 1°C for seedling emergence and each champ ber was illuminated with two ITT F AO/cv Coolwhite fluorescent bulbs. Seeds were planted in wooden flats containing Wedron White Silica (Wedron Silica Division, Del Mbnte Properties Co.) using a randomized complete block design. Rows were 15cm.1ong and 2cm apart with a planting depth of 8mm. Twenty seeds were planted per row. The seeded flats were irrigated daily using water of the same temperature as that of the chamber. Seedlings were considered emerged when the cotyledons were freed from.the growing medium. In instances where the seedlings emerged from the medium with the seed coat still attached, seedlings were considered emerged when the seed coat cleared the medium surface. Emergence was recorded daily and all emerged seedlings cut off at the medium.surface. Dormancy was considered broken when 50% of the seeds had emerged. MATERIALS AND METHODS Section II The effect of fruit age on the dormancy of the seed of peppers The effect of fruit age on the dormancy of pepper seeds was determined using seed from cultivars CMV 153k, CMV, CMV Resistant 2, and CMV Resistant 3 harvested from fruit at various stages of maturity. A11 plants were grown in the greenhouse from July, 1978 to October, 1978. Seeds were classified into three catagories depending on the stage of fruit maturity and color: Immature — the fruits were half green and half colored, approximately h8 days post anthesis; mature - color full, approximately 55 days post anthesis; overmature - full color with the initiation of fruit desication, approximately 65 days post anthesis. Two replicates of 30 seeds each were sown in a flat containing Wedron White Silica on October 10, 1978. Row dimensions, planting depth, temperature, irrigation, and emergence criteria fol- lowed that previously outlined. Emergence was recorded daily and the experiment terminated when emergence became asymptotic. l3 MATERIALS AND METHODS Section III The genetic control of dormancy in peppers The following 9, annuum cultivars were classified and used in this study: CMV 153h, CMV Resistant 2, and CMV Resistant 3 were classified as dormant while Big Boy was classified as non-dormant. All material was grown in the greenhouse from May, 1978 to September, 1978. Each cultivar was selfed one generation prior to hybridization. The one non-dormant parent and three dormant parents were hy- bridized reciprocally to obtain the various populations for the study. Three separate families were generated: Family I (Big Boy x CMV 153h), Family II (Big Boy x CMV Resistant 2), and Family III (Big Boy x CMV Resistant 3). P P F F2, and backcross populations were produced 1’ 2’ 1’ by hand pollination in a greenhouse. Seed was hand harvested from the fruit and air dried for A8 hours and then planted. All material was treated with 50 Arasan Red prior to planting. Three replications were used for each family with 20 seeds per replicate for the parental lines, 30 seeds per replicate for the F1 generation, and 60 seeds per replicate in the F2 and backcross gen- erations. Seeds were sown in wooden flats containing Wedron White Silica using a randomized complete block design with 15cm rows, 2cm apart. A planting depth of 8mm.was used. Temperatures were + held at 22.50C - 10C and irrigated daily with water of identical temperature. Emergence criteria followed that previously outlined. 1h 15 Means, variances, and standard deviations were calculated from individual plant data. Population means were statistically compared by the use of the 2-tailed t-test. Population data was analyzed by applying a chi-square goodness of fit. Since no significant differ- ences (5% level) were found between reciprocal F 's or between F2's, l the data were pooled for the genetic analysis (Table 2). 16 Table 2. Difference (d) between reciprocal F and F means and their corresponding standard errors for expressing dorman- cy in three pepper families Family Ix Family IIy Family IIIz Generation d SE d SE d SE Fl 0.73 2.59 2.27 2.5h 1.17 2.5h F2 3.28 3.00 0.19 2.77 1.0h 2.h2 xBig Boy x CMV 153k yBig Boy x CMV Resistant 2 zBig Boy x CMV Resistant 3 RESULTS AND DISCUSSION Section I The effect of dry storage on the loss of dormancy The period of after-ripening of the pepper seeds following ex- traction and storage varied with each cultivar. PI 260h3l had the longest after-ripening period with 61 days to reach 50% emergence while Big Boy had the least with a 1h day period to 50% emergence. All other cultivars were intermediate (Table 3). Holding the seeds in dry storage at 2h°C decreased dormancy for all cultivars except Big Boy, PI 281398, and CMV SA-218. These three cultivars had similar emergence patterns from the initial planting interval to the last planting interval (Table 3). A threshold for overcoming dormancy was noted at week six where time to 50% emergence leveled off for all cul- tivars. Since most of the environmental factors were kept constant, the variations observed in the length of dormancy and the subsequent loss of it suggested genetic differences for this character within the genus Capsicum. Initial rest requirements and the germination pattern of cultivars CMV 153h, CMV, CMV Resistant 2, CMV Resistant 3, and Big Boy suggested genetic variation for dormancy in Q, annuum.(Figure l). The cultivar Big Boy exhibited no dormancy and after-ripening while cultivars CMV 153A, CMV, CMV Resistant 2, and CMV Resistant 3 showed different levels of dormancy and after—ripening. Since the cultivars showing lower emergence percentages were cultivars with a long after—ripening l7 18 Table 3. The effect of after-ripening in pepper seeds on days to 50% emergence Length of storage at 2h°C prior to planting (in weeks) QEIEIXEE. 9. 1. 2. 3. i. .2 .2 PI 281398 16 16 1h 15 18 16 16 PI 260h31 61 56 A5 38 28 23 23 i» CMV SA—8 it CMV SA-37h CMV SA-218 19 18 15 15 1h 15 ' 15 CMV SAs91* CMV SA-217A 5h h2 36 20 16 17 16 CMV 971 26 20 21 13 13 15 1h CMV 972 2h 22 19 l8 13 15 15 CMV 153A 50 he 28 23 20 19 18 CMV 1535* CMV 1615* CMV 30 25 22 15 17 16 15 CMV Resist. 1 27 21 20 19 16 15 15 CMV Resist. 2 33 2h 20 l9 16 15 15 CMV Resist. 3 ho ' 31 25 20 19 15 15 * CMV 2063 Big Boy 1h 16 15 16 12 1h 1h * Denotes cultivars having less than 50% emergence. Figure l. The effect of dormancy and after-ripening on the emer- gence pattern for cultivars CMV 153h, CMV, CMV Resistant 2, CMV Resistant 3, and Big Boy sown immediately after harvest 2O IIOIIOIIIIIIII Vnn— >SU III M Hmfiwa >¢<2U .oI-lIu-o >Oo 0; I uUZuGGmSu O... m><fl nu‘u‘ — 550.“. 00 0Q 00— 0 398 3 W3 1N3383d 21 period, it is possible that a loss in vigor and/or seed decay could have decreased emergence due to the warm, moist environment encountered during after-ripening. High respiration rates have been equated with decreased seed vigor while seed decay could be caused by microbial attack under extended warm, moist periods (Copeland, 1976). There- fore, it is possible that these environmental conditions may have effected the emergence percentage. A high susceptibility to seed decay and/or vigor loss was evident for CMV Resistant 3. It appears that warm dry storage is necessary to overcome dormancy and still retain high emergence percentages. Tokumasu (1971) reported similar findings showing freshly harvested seed held in a saturated atmosphere delayed germination. RESULTS AND DISCUSSION Section II The effect of fruit age on the dormancy of pepper seeds Fruit age effected the dormancy period for the cultivars CMV 153A, CMV, CMV Resistant 2, and CMV Resistant 3 (Figures 2-5). Seed harvested from the overmature fruit emerged sooner for these cultivars although not always at a higher percentage than seeds harvested from mature fruit. Similarly, seed from mature fruit emerged earlier than those from immature fruit. This pattern suggested that after-ripening took place while still in the fruits and on the plant. Similar results were reported by 0dland (1938) in Cucurbits. Failure of cultivars CMV Resistant 2 and CMV Resistant 3 to emerge at the immature stage may have been a result of lower vigor and sus- ceptibility to seed decay or immature embryos. Similar findings were reported by Cochran showing seed germination was affected by pepper fruit maturity (193A). Conversely, cultivars CMV 153h and CMV had a moderately high emergence rate at the immature fruit stage suggesting a higher resistance to a loss of vigor or seed decay. 0r these two cultivars could have matured morphologically at a different rate than those of CMV Resistant 2 and 3. As a result, the higher germination percentages may have been due to a more advanced stage of development. 22 23 Figures 2-5. The effect of fruit age on the dormancy and seedling emergence for four pepper cultivars 2h HUI-Olu'. Op :2 0. On 90 On 0. a ' .\ 33¢: .\ \ I ‘0‘ O .\ 33(1- 95 .x n =3.- 23 .s .x .\ .uOIu‘u ~02 0.0 cane—(‘1. .83.!!- On u>¢0 0. On 00 O. 0' a a >‘U 02-3 ~02 9° ‘33. n .3...- >10 0 .30.. 38-03!- 2 nut. 3 on 3 3 o. o. o. 0‘ N .s 3: >3 .. 333. .. .s \\ .3231. . xx . . \. 8341-5 noun IND.“ RESULTS AND DISCUSSION Section III The genetic control of dormancy in peppers Due to a similarity in the results of the genetic control, dis- cussion of all three families will take place simultaneously. The modality expressed in the F2 frequency distribution of progeny from the crosses Big Boy x CMV 153k, CMV Resistant 2, and CMV Resistant 3 suggested that differences in dormancy between Big Boy and the other cultivars were controlled by a relatively few number of genes (Figures 6-8). Due to the absence of P type individuals, however, 2 a true estimate of the number or quantity of genes can not be ascer- tained. The F1 mean was skewed toward the non-dormant parent with partial dominance for non-dormancy indicated (Table h). No significant deviations from zero were found between Fl’ F and backcross gen- 23 eration means. In addition, the F2 and backcross generation means were located between the F1 mean and the dormant parental mean. The large variance recorded for the F generation may be due 1 to heterozygosity of one or both of the parents. Comparing the dis- tribution and variation of both parents, greater heterozygosity is noted for the P2 parent for Families I and III, but not Family II. The lower variance in Family II may be accounted for by a loss of 3h individuals (38% of the population). A greater number of individuals may have led to a higher variance since those not recovered probably had deeper dormancy than those recovered. The heterozygous condition 25 26 Figure 6. The emergence frequency distribution for parents, F , F2, BCl, and BC2 progeny from the cross Big Boy x CMV 153h NUMBER EMERGED 4O 2O 4O 20 4O 2O 4O 2O 4O 20 27 FIGURE 6 BC ,1 “2 IO 20 30 4O 50 60 DAYS TO EMERGENCE I \) (3) Figure 7. The emergence frequency distribution for parents, F1, F2, BCl, and BC2 progeny from the cross Big Boy x CMV Resistant 2 29 FIGURE 7 40 N 20 t 1,2 Omaamsm mania—Z 20 O 0 4O 20 4O 20 60 50 4O 30 20 10 DAYS 1'0 EMERGENCE Figure 8. The emergence frequency distribution for parents, Fl, F , BCl, and BC2 progeny from the cross Big Boy x CHV Resistant 3 NUMBER EMERGED 2O 4O 20 4O 20 4O 2O 20 A IO Ike JR. 31 FIGURE 8 'Vk'l. P1 '1 at:I ‘ 3C2 F2 20 so 40 DAYS TO EMERGENCE 50 60 32 Table A Population size, means, standard errors, parental range, and mid-parent values for the germination period in three Capsicum families Family Ix Family IIy Family IIIz Population N Mean SE N Mean SE N Mean SE P1 90 12.6h 1.02 90 12.6h 1.02 90 12.6h 1.02 P2 78 h3.h0 h.19 5h 27.56 1.58 79 3h.69 3.76 F1 115 17.52 3.38 112 16.52 3.29 116 15.79 3.15 F2 158 18.23 3.97 126 18.23 3.35 127 17.22 2.99 BCl 172 18.03 3.28 171 17.78 3.32 167 17.32 2.91 BC2 105 19.35 h.89 83 17.73 3.1h 92 19.59 n.6h Pl-P2, range A3 ' 23 35 Mid-parent 28.02 20.10 23.67 xBig Boy x CMV 153k yBig Boy x CMV Resistant 2 ZBig Boy x CMV Resistant 3 33 of the P2 parent could affect skewness of the BC2 and F2 population means as noted. It is also possible that skewness may have been a result of the loss of a high number of individuals in the BC2 and F2 generations with the P 2 type expression. The heterozygosity and reduced germination percentages in the parental generation and the F2 and BC2 generations may be explained by the presence of semilethal genotypes. The genotype which expresses delayed germination phenotypically may also give the seed the disad— vantage of extended exposure to warm, moist conditions, hence reducing the chances of the seed to germinate by succumbing to disease or reduced vigor. This is evident by the percentages observed in this study and the study in Section I where the P2 emergence percentages were 86% and 66% (CMV 153h), 60% and 60% (CMV Resistant 2), and 86% and 22% (CMV Resistant 3) respectively. In light of this evidence, the F and backcross populations 2 were partitioned into non-dormant and dormant types based on the ob- served modality in Figures 6, 7, and 8 assuming a normal distribution of P1 and P2 phenotypes and all individuals not recovered were of the dormant genotype. The following genetic model is proposed: Three major genes (designated A, B, Q) constitute Pl (Big Boy) and P2 (CMV 153k, CMV Resistant 2 and 3) for expressing either non-dormancy or dormancy. The proposed genotype for Big Boy is AABBCC and is non- dormant while the genotype for CMV 153A, CMV Resistant 2 and 3 is aabbcc. The F1 genotype is AaBch and is non-dormant (Figure 9). A (3:1)(15:1) factorial gene model is suggested by the observed F2 and backcross ratios assuming all non—recovered individuals to be dormant. §:_conditions the non-dormant expression when at least one Figure 9 Pl (Big Boy) 00 3h Gene model for dormancy in peppers AABBC___(_:_ - non-dormant P2 (CMV 1531;, Resistant 2 and 3) _\ 2d0rmant - a_a____bbcc Fl AaBch - non-dormant A-B-C- A-bbC- Non—dormant aaB-C— A-B-cc A—bbcc aaB-cc Dormant aabbC- aabbcc Ratio h5:l9 35 dominant gene is present either at the A, B) or both loci.- 9:.shows partial dominance. Recessive homozygosity at the g_1ocus expresses dormancy although A;and BDmay modify its expression. Mereover, the homozygous recessive A.and B_loci are epistatic to a dominant g_and express dormancy. The F2 generation genotypes A—B-C-, ArbbC-, and aaB-C- are non-dormant, while A-B-cc, Apbbcc, aaB-cc, aabbC-, and aabbcc are dormant. The ratios expected (non-dormant:dormant) from the (3:1)(15:1) factorial gene model are h5:19 and 1:1 for the F 2 and BC2 generations respectively. An acceptable fit was obtained for both the F2 (P= 0.5-0.1 Family I, P= 0.5-0.1 Family II, P= 0.9-0.5 Family III) and B02 (P= 0.9-0.5 Family I, P= 0.5—0.1 Family II, P= 0.5-0.1 Family III) generations (Table 5). The BCl generation was not testable because 0 was the expected frequency in one of the classes. However, the observed ratios recorded do not approximate the expected phenotypes. A modifier may be influencing this generation, delaying the emergence of some of the progeny. 36 Table 5, Distribution and chi-square analysis of F and backcross progenies of crosses between dormant and non-dormant plant types for three different pepper families. No. of Seedlings Population Total Dormant Non-dormant Ratio P Family I Big Boy 90 0 9O — _ CMV 153A 72 72 0 - - F1 120 12 108 - - F2 180 A8 132 19zh5 0.5-0.l BCl 180 22 158 0:1 - 1302 180 87 93 1:1 0.9-0.5 Family II Bis Boy 90 0 90 — - CMV Resist.2 5h 5h 0 — - F1 120 15 105 - - F2 180 61 119 19:h5 0.5-0.l BCl 180 23 157 0:1 - BC2 180 100 80 1:1 0.5-0.l Family III Bis Boy 90 o 90 - - CMV Resist.3 79 79 0 - - F1 120 7 113 - - F2 180 57 123 l9:h5 O.9-0.5 BCl 180 25 155 0:1 - BC2 180 101 79 1:1 O.5-O.l SUMMARY AND CONCLUSION Genetic variation was found for the expression of dormancy in seed germination and emergence in four species of Capsicum. Cultivar response to fifty percent emergence ranged from 1h days to 61 days when planted immediately after harvest from mature fruit. Fruit age was also shown to affect dormancy; dormancy increased with decreased fruit age. This would support the idea that after-ripening of the pepper seeds was occurring while still attached to the mother plant. Gutterman (1978) reported the maternal environment had a pronounced effect on the germinability of seeds as a result of internal changes in hormonal levels. From this it would seem that the after-ripening of the seeds was independent of the maternal plant since after-ripening occurred both attached to and removed from the mother plant. Reduced germination was associated with increased dormancy suggesting a loss of vigor or seed decay encountered during after- ripening when planted immediately after harvest from.mature fruits. Warm dry storage was shown to be effective in overcoming rest while still maintaining a high level of germination. The seeds appeared to develop the capacity to break down the inhibitory activity under such conditions. Hull (1937) reported similar results in peanuts with storage at 25°C much more effective in overcoming dormancy than at 300. The progenies of reciprocal crosses between three families of g, annuum were evaluated to determine the mode of inheritance of dormancy. Partial dominance for the non-dormant parent was noted. Progeny 37 38 mortality in segregating generations made quantitative analysis invalid for all families. Lack of P2 individuals in all families may have been the result of an interaction of Big Boy with the dormancy parents. The penetrance and recovery of a dormant phenotype may have been decreased by a dominant factor in Big Boy. Heterozygosity and reduced germination found in the dormant parental generation and the F F l’ and BC generations was explained by the presence of semilethal 2’ 2 genotypes. Extended exposure to warm, moist environmental conditions resulted in a decline in germination. (Chavagnat (1978) reported heterogeneity to be important in the germination of Lavandula L. seeds. Heterogeneity was said to be due to the quality of the seed, the percent of seed that was dormant and the depth of dormancy. Since dormancy has been reported as a survival mechanism.(Harper and McNaugh- ton, 1960), survival may be enhanced by the presence of heterozygous genotypes, extending the chances of a species' seed to germinate and survive under a favorable environment. Such may be the case for Capsicum. Ratios obtained by partitioning segregating generations into phe- notypic classes suggested a three gene system (designated A, B) Q) for the expression of dormancy. A (3:1)(15:1) factorial model of the three genes best explained the observed ratios with the Pl paren- tal line designated AABBCC and the P parental lines designated aabbcc. 2 A modifier appeared to influence the expression of the trait. This model is tentative, however, due to the assumptions made and further investigation is needed to verify the genetic control of dormancy in peppers. THE INHERITANCE OF SEVERAL CHARACTERISTICS IN PEPPER II THE INHERITANCE OF COLD EMERGENCE IN PEPPERS INTRODUCTION Currently peppers grown in Michigan and other areas of similar climate are established through the use of transplants. Although transplanting peppers is effective in decreasing the length of the growing season while still obtaining a quality product, there are problems and uncertainties such as poor initial growth, disease, and limited choice associated with this method. Establishing peppers by direct seeding would have the advantages of lower cost per acre, lower labor costs, flexability in varietal choice, and disease control (Johnson and Wilcox, 1972). Being a warm season crop, the tempera- tures for optimum germination in peppers are between 20 - 30°C. Under these conditions seeds should germinate quickly and uniformly. Un- fortunately, soil temperatures range from 10 - 18°C at the time when direct seeding should be made. At this temperature, however, ger- mination and growth of the pepper seeds would be retarded. Genetic variation in the ability of peppers to withstand mod- erately cold temperatures has been reported by Gerson and Honma (1978). In the study it was shown that several cultivars were able to germinate and emerge at temperatures of 13 - 15°C. However, most of the cul- tivars that expressed quick emergence under the suboptimal conditions were of non—commercial types. To insure improved crop stands at low soil temperatures by direct seeding, it would be necessary to incorporate this trait into commercial cultivars. The purpose of this study was to identify the genetic control in the ability of peppers 39 hO to germinate and emerge at low soil temperatures. LITERATURE REVIEW During cold wet conditions encountered during early spring plantings, a major problem in direct seeding is the failure to attain a uniform stand with rapid emergence (Robinson and Mayberry, 1976). Several methods have been used for hastening emergence for uniform stands under such conditions. Hardening of seeds was shown to improve _ germination in several crops. By soaking seeds for twenty-four hours and then drying them for twenty-four hours, carrot seeds which were hardened had a higher rate of germination than those that were un- treated (Austin, 1969). Similar results were reported in two cultivars of corn (Hegarty, 1970). In addition, seed soaked in water and sown in a moist condition also germinated sooner than dry seed (Kid and West, 1918). Germination has been accelarated by the method of osmotic pre- treatment (Heydecker, 1973). With this method seeds are allowed partial imbibition and the initial processes of germination without radicle emergence via an osmotic potential. An increase in rate and earliness of germination was shown in onions (Heydecker, 1975) while uniformity of germination was noted with celery (Salter and Darby, 1976). Inorganic salts have been used to improve seed germination. Ells (1963) reported the germination of tomato seeds at 100C night temperatures were stimulated following K POh and KNO treatments. 3 3 Similarly, methods of treating tomato seeds with aerated nutrient hl A2 solutions to increase germination rates was shown by Oyer and Koehler (1966). Pregerminated seed has been used to increase germination rate and uniformity. Biddington, 22.2l: (1975) reported that pre—germinated celery seed sown in a fluid gel germinated earlier with increased emergence as compared to dry seed. Taylor (1977) has indicated seed that germinates slow, especially'at low temperatures, benefited most from pregermination. Genetic variability in the ability to germinate under sub-optimal conditions has been reported in a number of different crops. Varietal response to growth rate and germination in tomato at low temperatures was reported by Kemp (1967) and Smith and Millet (1973). Similarly, Pinnell (19h9) has shown wide differences between corn inbreds in the ability to germinate at low temperatures which appeared heritable in crosses as did Jones and Peterson (1976) in rice. Selection pro- duced a 20 - 30% improvement in the rate of germination in sugar beets indicating that the character was heritable (Wood, 1952). Littlejohns, ep_gl, (1976) reported differences in emergence among soybean cultivars at 10°C but not at 20°C and 30°C. Moreover, Gerson and Honma (1978) showed genetic variability in emergence within species and between species in Capsicum.at low temperatures. Heritability estimates were obtained for the control of time to germination in tomato (Whittington and Fierlinger, 1972). The in- heritance was largely additive and closely related to seed size. El Sayed and John (1973) found the inheritance of tomato emergence at different temperatures to be quantitative with an estimated 2h gene pairs. There was strong evidence for additive gene action. Cannon, A3 EE.2$: (1973) reported the germination of the tomato at 100C to be inherited by a single gene. Similarly the emergence of tomato seed- lings at low temperatures was highly heritable and suggested to be controlled by 3 - 5 genes (Ng and Tichelaar, 1972). MATERIALS AND METHODS Section I Evaluating the emergence response of the pepper at low soil temperatures One hundred thirty-seven accessions of Capsicum baccatum.var. pendulum were used in evaluating emergence response at low soil tem- peratures, hereafter referred to as cold emergence. Two accessions were obtained from Dr. Paul Smith, University of California, Davis and one hundred thirty-five accessions from the Southern Regional Plant Introduction Station, Experiment, Georgia. All of the seed used in this study was grown in greenhouses at Michigan State university from May, 1977 to September, 1977. During this period, normal cultural practices were followed. All seed was harvested by hand from fully ripe fruit approximately 55 t 5 days after anthesis depending on the accession and air dried for h8 hours. Prior to sowing, all seeds were treated with 50 Arasan Red. Two replicates of 25 seeds from each accession were planted on October 20, 1977 and placed in four temperature controlled chambers; one replicate per chamber. Temperatures were held at 13°C : 1°C in two chambers and 10°C : 1°C in two chambers for seedling emergence and each chamber was illuminated with two ITT F ho/cv Coolwhite fluo- rescent bulbs. Seeds were planted in wooden flats containing Wedron White Silica (Wedron Silica Division, Del Monte Properties Co.) using a randomized complete block design. Rows were 15cm long and 2cm apart with a hh AS planting depth of 8mm. Twenty-five seeds were planted per row. The flats were irrigated every other day with water of the same temperature as that of the chamber. Seedlings were considered emerged when the cotyledons were freed from the growing medium. In instances where the seedlings emerged from the medium with the seed coat still attached, seedlings were considered emerged when the seed coat cleared the medium surface. Emergence was recorded daily and all emerged seedlings were cut off at the medium.surface to facilitate counting. Sampling continued for seventy-five days. An emergence index (EI) for each accession was calculated using the formula: = Sum(Days To Emergence)(Number Emepged) Total Number Emerged EI This index was adopted from.that used to measure low temperature sprouting of tomatoes (Smith and Millet, 1973). The formula provides an average for emergence that favors early emergence. The lower the value calculated, the better the response to cold emergence. MATERIALS AND METHODS Section II The genetic control of the emergence response of the pepper at low temperatures Four accessions of g. baccatum var. pendulum were used in de- termining the genetic control of cold emergence: 2033 and PI 257185 were classified as early emerging lines while PI 260593 and PI 281310 were classified as late emerging lines. All material was grown in the greenhouse from May,l978 to September, 1978. Each cultivar was selfed one generation prior to hybridization. The two early emerging parents and the two late emerging parents were hybridized reciprocally. Four separate families were generated: Family I (2033 x PI 260593), Family II (2033 x PI 281310), Family III (PI 257185 x PI 260593), and Family Iv (PI 257185 x PI 281310). Pl, P F 2, F BC 1’ 2, and BC populations were produced by hand pollination 1’ 2 in a greenhouse. Seed was hand harvested from the fruit and air dried for A8 hours. All material was treated with 50 Arasan Red prior to planting. Five replications were used for each family with 20 seeds per replicate for the parental lines, 30 seeds per replicate in the F 1 generation, and 60 seeds per replicate in the F and backcross gener- 2 ations. Seeds were sown in wooden flats containing Wedron White Silica using a randomized complete block design with 15cm rows, 2cm apart. A planting depth of 8mm was used. Temperatures were held at A6 w 130C I 100 in a temperature controlled chamber and irrigated every other day with water of identical temperature. Emergence criteria followed that previously outlined. Means, variances, and standard deviations were calculated from individual plant data. Population means were statistically compared by the use of the 2—tailed t-test. The conformity of the data to the additive-dominance model by Mather's A,B,C scaling test was used (Mather and Jinks, 1971). The equations used for this test were: A=2§El-Fl-Pl,s=2RE2-Fl-Pz,c=hF2-2Fl-Pl-P2. Significance was obtained by computing the standard error of the corresponding population means and applying a 2-tai1ed t-test. Sig- nificance suggested the existence of non-allelic interactions. Estimates of additive (D), dominance (H), and environmental (E) variances were obtained by the equations: E = vFl’ H = h[(VBCl+ VBC2- VF2) - VFl], and D = 2[VF2- (l/uH + E)] (Mather and Jinks, 1971). Narrow and broad sense heritability estimates were computed as the D ratio of additive genetic variance to phenotypic variance (D+H+E) and D+H the ratio of total genetic variance to phenotypic variance (D+H+E) respectively. The genetic advance of the trait was calculate using methods described by Allard (1961). Since no significant differences (5% level) were found between reciprocal Fl's and between F2's, the data were pooled for the genetic analysis (Table 6). h8 Table 6. Difference (d) between reciprocal F and F means and their corresponding standard errors in four pepper families for the ability to emerge at cold soil temperatures Family Iw Family IIx Family IIIy Family Ivz Generation 0. SE 0. SE 0. SE 0. SE Fl 6.51 11.82 3.69 12.h7 8.95 9.90 8.29 10.36 F2 _ 5.89 11.52 10.62 10.21 0.93 7.16 5.75 9.51 w2033 x PI 260593 x2033 x PI 281310 yPI 257185 x PI 260593 zPI 257185 x PI 281310 RESULTS AND DISCUSSION Section I Evaluating emergence response of the pepper at low soil temperatures Table 7 shows the means and range in days to emergence of 119 pepper cultivars at 13°C and 10°C. Mean emergence differences be- tween temperatures were significant (5% level) showing a much slower rate at 10°C opposed to 13°C. Table 8 shows the preformance of 137 cultivars at 100C and 13°C. Of the total number of cultivars screened, eighteen cultivars failed to germinate at either temperature. Also a lower number of cultivars were able to germinate and emerge at 100C than at 13°C suggesting a threshold for some cultivars in the ability to germinate between these two temperatures. In general, cultivars exhibiting superior emergence at 1300 did so at 1000. The emergence index for among cultivars was significantly different (5% level) at 130C but not at 100C. Cultivar 2033 had the lowest mean emergence index of 22.10 which was signifi- cantly different (5% level) than 107 other cultivars at 130C. 2033 also had the lowest mean emergence index of h0.57 at 100C. Differences in emergence rate of the cultivars at 130C suggested wide genetic vari- ability for this character. Cultivar PI 281310, on the other hand, had the highest mean emergence index of h3.08 at 130C. However, cultivars PI 213915, PI 257183, and PI 2605h5 had the highest mean emergence index of 71.00 at 100C. Moreover, cotyledons of seedlings emerging at 10°C were yellow to virescent in color suggesting a threshold 1&9 Table 7. Mean emergence indices, ranges, variances, and standard errors for 119 cultivars of pepper as affected by low soil temperatures Temperature N Mean Range 52 SE 0C -———————days 13 119 31.68* 22.10 - 93.08 10.18 3.1h 10 99 5h.32* no.57 - 71.00 329.27 18.1h *Significant at the 5% level 51 Table 8. Origin and performance of 137 pepper cultivars at low soil temperatures Emepgence Index?O Cultivar Origin 13 C 10 C 2033 Paul Smith 22.10 90.57 PI 257185 Peru' 29.01 60.92 PI 159299 Georgia 26.00 57.85 PI 291658 Peru 26.00 50.93 PI 215700 Peru 26.80 51.67 PI 291669 Peru 27.33 59.99 PI 199506 B. Guiana 27.66 58.78 PI 257189 Peru 27.79 57.80 PI 281906 Peru 27.82 52.99 PI 260580 Bolivia 27.95 53.99 PI 257199 Peru 28.15 69.33 PI 257159 Columbia 28.19 50.66 PI 291679 _ Chile 28.33 62.33 PI 257163 Peru 28.35 99.00 PI 238063 Peru 28.91 56.09 PI 159235 Georgia 28.57 55.00 PI 260551 Peru 28.80 55.00 PI 257157 Peru 29.00 68.00 PI 257161 Peru 29.19 63.66 PI 260988 Bolivia 29.25 — PI 291662 Peru 29.28 66.00 PI 257173 Peru 29.30 65.00 PI 291659 Peru 29.35 59.99 PI 260560 Bolivia 29.39 53.08 PI 291679 Ecuador 29.90 59.99 PI 159295 Georgia 29.92 - PI 260570 Bolivia 29.92 69.50 PI 260583 Bolivia 29.99 61.81 PI 188803 Philippines 29.97 65.67 PI 281936 Hawaii 29.99 97.73 PI 260590 Bolivia 29.53 - PI 257169 Peru 29.59 61.00 PI 290983 Peru 29.58 57.28 PI 260589 Bolivia 29.59 62.60 PI 257122 Columbia 29.67 58.86 PI 229990 Costa Rica 29.78 59.00 PI 257169 Peru 29.95 59.80 PI 291656 Peru 29.99 63.00 PI 260561 Bolivia 29.99 - PI 159272 Georgia 30.10 60.70 PI 257177 Peru 30.16 - PI 260559 Bolivia 30.18 57.82 LSD 6.29 (5% level) Table 8.(continued) Emergence Index Cultivar Origin 1300' IOUC PI 260587 Bolivia 30.20 62.56 PI 257179 Peru 30.37 65.67 PI 281308 Bolivia 30.90 - PI 257135 Ecuador 30.99 62.99 PI 315025 Peru 30.53 51.50 PI 260595 Brazil 30.62 71.00 PI 159279 Georgia 30.69 62.50 PI 260591 Brazil 30.79 59.00 PI 260592 Brazil 30.90 62.80 PI 260539 Argentina 31.00 63.67 PI 281300 Argentina 31.05 62.82 PI 257139 Ecuador 31.06 - PI 260506 Peru 31.07 63.00 PI 159267 Georgia 31.11 65.67 PI 260590 Argentina 31.17 66.25 PI 291698 Peru 31.28 63.33 PI 257153 Peru 31.31 67.11 PI 257183 Peru 31.35 71.00 PI 260579 Bolivia 31.92 62.67 PI 260592 Brazil 31.97 53.50 PI 260581 Bolivia 31.97 61.80 PI 370010 India 31.97 53.53 PI 257133 Ecuador 31.56 65.99 PI 188981 Peru 31.73 63.99 PI 260599 Peru 31.80 52.50 PI 257179 Peru 31.88 60.50 PI 260589 Bolivia 31.88 62.70 PI 281390 Ecuador 31.88 69.25 PI 260571 Bolivia 31.90 63.67 PI 257130 Columbia 31.92 69.28 PI 260593 Brazil 31.99 - PI 152239 Peru 32.12 58.33 PI 260536 Argentina 32.30 59.17 PI 159299 Georgia 32.35 57.33 PI 159260 Georgia 32.90 63.00 PI 260538 Argentina 32.92 63.00 PI 260552 Peru 32.96 - PI 355819 Ecuador 32.97 - PI 266092 Mexico 32.50 - PI 257186 Peru 32.67 68.00 PI 260598 Peru 32.73 - PI 159270 Georgia 32.91 - PI 281321 Chile 32.99 52.50 LSD 6.29 (5% level) Table 8.(continued) 53 Emergence Index Cultivar Origin 13°C 100C PI 159259 Georgia 33.06 95.50 PI 281311 Brazil 33.08 60.00 PI 238062 Brazil 33.12 - PI 260960 Peru 33.20 PI 257152 Peru 33.28 PI 281307 Bolivia 33.33 - PI 260550 Peru 33.99 _ PI 260579 Bolivia 33.67 - PI 290982 Peru 39.08 PI 281313 Brazil 39.32 60.00 PI 291662 Peru 39.35 66.00 PI 260591 Brazil 39.62 - PI 260562 Bolivia 39.83 - PI 260566 Bolivia 39.86 - PI 337522 Argentina 39.93 60.88 PI 293399 Peru 39.99 55.71 PI 257193 Peru 35.25 - PI 260569 Bolivia 35.33 - PI 281937 USA 35.38 63.00 PI 260576 Bolivia 35.57 - PI 213915 Bolivia 35.83 71.00 PI 281908 Peru 36.23 - PI 257180 Peru 36.33 - PI 215791 Peru 36.38 - PI 215727 Peru 36.99 60.00 PI 260563 Bolivia 36.88 - PI 215739 Peru 36.89 66.00 PI 281919 Peru 36.92 - PI 281907 Peru 37.22 - PI 260572 Bolivia 37.50 - PI 273920 Netherlands 37.50 PI 260565 Bolivia 37.91 - PI 260593 Brazil 90.25 — PI 281310 Brazil 93.08 — LSD 6.29 (5% level) Cultivars which failed to germinate 2039 ** PI 260569 Bolivia PI 257191 Peru PI 260575 Bolivia PI 257150 Peru PI 260578 Bolivia PI 257151 Peru PI 260585 Bolivia PI 260958 Brazil PI 266091 Mexico PI 260535 Argentina PI 267729 Guatemala PI 260596 Brazil PI 281309 Brazil 59 for chlorOphyll formation may be between 10°C and 130C. Seedlings with yellow cotyledons when placed in the greenhouse became green within five days or failed to turn green. It appears that seedlings which failed to turn green were susceptible to the cold temperatures. The secondary leaves which emerged in the greenhouse from plants with green and yellow cotyledons were green suggesting no permanent dam- age to the plant as a whole. RESULTS AND DISCUSSION Section II The genetic control of the emergence response of the pepper at low temperatures Results of Mather's A,B,C scaling test are shown in Table 9. Non-significant deviations from.zero (1% level) were found in all four families suggesting that epistasis was not involved in the in- heritance of cold emergence. Hence the additive-dominance model was determined adequate for the analysis of the data. In addition, data was grouped into three day classes for frequency distribution analysis. Family I (2033 x PI 260593): The F2 frequency distribution of progeny from the cross 2033 x PI 260593 suggested that differences in cold emergence between these two cultivars were controlled by a few number of genes (Figure 10). The F1 mean was slightly skewed toward the P2 mean (Table 10) with partial dominance for slower germination at low temperatures. In addition, the F2 and BCl means fell between the F1 mean and the P2 mean. The BC2 mean exceeded that of the P2 mean suggesting a preponderance of genetic effects expressing a slower emergence at low temperatures for the population. Transgressive vari- ation was noted in the F BC and BC generations showing individuals 2’ l’ 2 which exceeded those of the P2. The F1 did not deviate significantly (5% level) from the mid-parental value, suggesting that non-additive gene action is not a major contributor in the expression of the charac- ter (Ketata, pp 91,, 1976). However, the F1 also did not deviate 55 Table 9. Estimation for the adequacy of using the additive-dom- inance model for Families I, II, III, IV by Mather's A,B,C scaling test. Scaling Test ~ w Parameter Family I Family IIX Mean SE Mean SE A 50.19 25.63 52.57 27.29 B 39.21 29.79 25.69 26.98 C 77.91 63.38 57.89 61.06 FamilyIIIy Family 172 Mean SE Mean SE A 29.98 23.18 92.70 28.37 B 2.82 21.86 10.19 22.86 C 28.30 98.59 38.51 66.99 W2033 x PI 260593 X 2033 x PI 281310 yPI 257185 x PI 260593 2 PI 257185 x PI 281310 ‘1 ‘Jl Figure 10. The emergence frequency distribution for parents, F , F2, BCl, and BCQ from the cross 2033 x PI 260593 NUMBER EMERGED 3O 20 IO 45 30 I5 45 3O 45 30 I5 45 30 IS IO . . .- 0...... .0 0.; FIGURE IO . .I'. o I . u u as °~Q o 5.0 o. ‘1’. II o ‘3 e no 7 '0" ' 9"... D 1 o. I U D .0 I o '- 4 R 00 O. Q.’O . .‘ . ’. C ' D O C 0' ‘ I. I. I... ono"o' % ‘O.’..o 0". U a 0'. J. .3 '0' °" ‘0. o”..."o ’ "ADI .I."" 30 50 70 DAYS TO EMERGENCE 0‘...o‘ 90 oamawm Ha s mosemm Has momoem Ha a mmsamm Has camawm ed a mmoms mamoem ad a mmom: ao.ma He.o Hm.w mn.oa ecosmmuoas Lam Hm.ea ma.ms mm.ea me.ms economies: mm mm on He omens .mansa mm.OH mo.bm mwa mm.oH wa.>> mp mm.oa Hm.ow mam mm.ma mm.:> wma mom my mm.ma Nm.:w Nam mm.HH mm.mm 03m mo.HH mm.am mam N©.ma wo.>w mmm Hum Ha.ma mm.mm mam Hm.:H ma.»m mwa Pm.HH Hm.mm 0mm mm.:H ®>.mw wwa mm mm.» mm.om wad mm.oa >®.®: moa mm.m :m.mm Nma 0:.w mm.~m :HH Hm sa.m em.me so am.m am.ae be aa.m em.me so mm.m am.ao on ma m:.m mo.wm we m:.m mo.~m we ::.m om.:m on ::.m om.:m ow Hm mm new: 2 mm coo: 2 mm one: 2 mm new: 2 :ofipmadmom s>HaHessa aHHH nausea HH aaassa H aaassa x 3 monopmaomSop Hflom 30H pm -mmsoeo ow hpflawpm pom mowaflemw Edowmmmo asoa 2H mozam> psopmmlewa 80am :oflpmfi>op me one modao> pcoammlefle .omcma Hmpnoamm .maoaao camecmpm .mcmoa .ouwm ooflpmddmom .oH manna 60 significantly (5% level) from the P2 mean which also suggests that non- additive gene action does contribute to the expression of the trait. The contradiction of these results may be due to low progeny re- covery in the F2 and backcross generations skewing population means. Additive variance (D) appeared to be the most important factor (52% of the total phenotypic variance) contributing to the genetic con- trol of cold germination and emergence (Table 11). Dominance variance was positive and smaller than the additive (D) variance in determining cold emergence. Heritability estimates were moderate to high for the trait with narrow and broad sense heritability estimates of 0.52 and 0.82 respectively. The value for expected genetic advance (G.S.) is reported in Table 11 as 15.63. Expected genetic advance shows the possible gain from selection as percent increase in the F3 over the F2 mean when the most desirable 5% (K = 2.06) of the F2 plants are selected. Heritability and genetic advance generally agreed in showing characters for which selection in the F2 would lead to substantial improvement. Therefore, reporting genetic advance and heritability estimates should be more informative in genetic and breeding studies than showing either of them alone. These estimates may again, however, be biased due to the low number of individuals recovered in the P2, F2, and backcross generations. 1‘ Family II (2033 x PI 281310): The F2 frequency distribution of progeny from the cross 2033 x PI 281310 suggested that differences in cold emergence between these two cultivars were also controlled by a low number of genes (Figure 11). The F1 mean was skewed toward the P2 mean (Table 10) with dominance for Slower germination at reduced 61 Table 11. Estimates of components of variation; environmental (E), additive (D), dominance (H), and total phenotypic (T) variances, heritability, and genetic advance for cold emergence in four pepper families Families Component IW* Ifxi IIIy* Ivz* E 70.65 38.66 109.79 60.69 D 218.86 89.99 378.92 998.26 H 131.36 211.16 -286.12** -101.53** T 920.87 339.31 983.16 508.95 Heritability for F2 Narrow 0.52 0.26 0.78 0.88 Broad 0.83 0.89 0.78 0.88 Genetic advance 15.63 6.25 29.20 23.90 W2033 x PI 260593 §2033 x PI 281310 JPI 257185 x PI 260593 zPI 257185 x PI 281310 * Estimates may be biased due to the low number of individuals recovered in the various populations ** Negative values can be interpreted as zero 7\ to Figure 11. The emergence frequency distribution for parents, F1, F2, B01, and BC2 progeny from the cross 2033 x PI 281310 FIGURE II a. u . .. u on '00 u . . . u I a o I 00 o o a. a a . I .. .. .v o o 2 e c .- 00! F 000 B . ’. D‘A- f o A 0 0I o .. ... .. I. O... ... I II C. a D. co 00 ‘II I \ co III a I I I I I I I 0~ ‘I 00 o. ’0 o 00 000 co 00 000 O I. 00 o o I oo 000 o l I O O O U 2 O O. .. I ... no a w .. o o A u .. .. a I Omfiuuzm zunSq—Z 9O 7O 50 30 IO DAYS TO EMERGENCE 69 temperatures also indicated. The F2 and BC2 generation means fell between the F1 mean and the P2 mean while the BCl generation mean was slightly skewed toward the Pl mean. Transgressive variation was noted in the F2 and backcross generations showing individuals which exceeded those of the P2 population. Dominance variance (H) appeared to be the most important factor (62% of the total phenotypic variance) contributing to the genetic con- trol of cold emergence. Additive variance (D) was positive and smaller than the dominance variance (H) (Table 11). Heritability estimates were moderate to low for the trait with narrow and broad sense heri- tability estimates being 0.26 and 0.89 respectively. The value for expected genetic advance (G.S.) is reported in Table 11 as 6.25 and shows the possible gain from selection as a percent increase in the F3 over the F2 mean when the most desirable 5% (K = 2.06) of the F2 plants are selected. A preponderance of dominance effects along with moderate heritability and genetic advance obtained in this family sug- gests that selection for this character would be moderate to low. Family III (PI 257185 x PI 260593) and Family IV (PI 257185 x PI 281310): The F2 frequency distribution of progeny from these two families suggested that differences in cold emergence between the two parents were controlled by a small number of genes (Figure 12 and 13). The F1 mean was slightly skewed toward the P2 mean (Table 10) with partial dominance for slower germination at low temperatures also suggested. In addition, the F2 and BCl means were located between the F1 mean and the P2 mean. The BC2 mean exceeded that of the P2 mean suggesting a preponderance of genetic effects in this population expressing a slower emergence at low temperatures. Transgressive ()\ \JI Figure 12. The emergence frequency distribution for parents, Fl, F , BCl, BC2 progeny from the cross PI 257185 x PI 2 0593 NUMBER EMERGED 30 20 IO 45 30 I5 45 30 45 30 45 30 66 FIGURE I2 0 :u': P e 0 2 o I I I ... ... .' 3.. a , '..' ‘. O I ‘00.... O o". ‘0 0'0 .0 e .0 I .... ‘0' .9. ,o'“. ‘O at.” ‘ a“. BC 4’ s. 1 e 0‘ A : . 0 ‘ e' .0 f ‘0 o O. ‘9 once-Iouol‘. 0...... O. . .... g .. ...-5 0‘ I 05 ‘ o o oo 9 ' ........--............... ’ .’. .... . ' '0 e '0. . ... 0: .. 0'... ..... .... '0'. I I . .....C....... I ‘ .Q'. .. . . .‘... '0 so so 70 90 DAY TO EMERGENC E 67 Figure 13. The emergence frequency distribution for parents, F , F2, BCl, and B02 progeny from the cross PI 257185 x PI 281310 NUMBER EMERGED 3O 20 IO 45 30 I5 45 30 45 30 45 30 I 5 68 FIGURE 13 ‘ ..J: P P i I I o : 2 I. ' .... . :u ' .0 ..." ...-.- O’. ...... 0 ‘. o 9 I .0 Id. ..4 ... .... you... O ..., 3C 0’ ° I 0' .9 .0 ‘. .0 ' 09’ o o. ‘0 1" ............ ....O 2 ’5. * ‘ o ‘ o f .0 0. .fi. .0 .... » ...-IIOIOCC’ ...." F J 2 '0‘. .0 9 O 5' .o .. ..‘.~. ugofl . .v‘ o..... ’ 0......“ IO 30 5O 7O 90 DAYS TO EMERGENCE 69 variation was noted in the F2 and backcross generations showing indi- viduals which exceeded those of the P2. Additive variance (D) appeared to be the most important factor (78% in Family III and 88% in Family IV of the total phenotypic vari- ance) contributing to the genetic control of cold emergence (Table ll). Dominance variance (H) was negative which may have been the result of a sampling error, or large environmental variance (E), a large F2 variance along with a lower than normal variance in the backcross generations along with low progeny recovery. The heritability es- timates were high (0.78 in Family III and 0.88 in Family IV). However, these estimates may have been biased due to the negative value for the dominance variance. The value for expected genetic advance (G.S.) is reported in Table ll as 29.20 (Family III) and 23.90 (Family IV). Expected genetic advance shows the possible gain from selection as percent increase in the F3 over the F2 mean when the most desirable 5% (K = 2.06) of the F2 plants are selected. SUMMARY AND CONCLUSION Genetic variation was found for the expression of cold germination and emergence in.g, baccatum var. pendulum. Cultivar response to emergence at 130C ranged from an emergence index of 22.10 (cultivar 2033) to h3.08 (cultivar PI 28l310) while an emergence index range of no.5? (cultivar 2033) to 71.00 (cultivar PI 213915) was found at 10°C (Table 8). Mean emergence differences between temperatures were significant (5% level) showing a much slower rate at 10°C opposed to 13°C (Table 7). In general, cultivars exhibiting superior emergence at 1300 did so at 1000. Similar findings have been reported in tomatoes (El Sayed and John, 1973), maize (Pinnell, l9h9) and cucumber (Lower, l97h) for germination at suboptimal temperatures. Seedlings which emerged at 10°C were found to be yellow to vire- scent in color suggesting a threshold for chloroplast development be- tween 10 and 13°C. Apparently temperatures at 10°C were too low for normal chloroplast development resulting in the lack of chlorophyll in the cotyledons. The progenies of reciprocal crosses between four families of g. baccatum.var. pendulum.were evaluated to determine the mode of in- heritance of cold emergence. Partial dominance for slow emergence at low temperatures was noted. Additive and dominance gene action played a role in trait expression with additive gene action most important in families I, III, and IV while dominance gene action was greatest in Family II (Table ll). Low progeny recovery in families 70 71 I, III, and IV, however, may have biased those estimates. In addition, frequency distributions in all families generally agreed with the re- sults in Family II for dominance gene action. In Family III and IV, with PI 257185 as a common parent, dominance variance was negative. This was accounted for by the genetic interaction of PI 257185 with the other parents producing a large environmental variance, a large F2 variance, or an unusually small backcross variance in addition to low progeny recovery. Narrow sense heritability estimates ranged from 26% to 88%, while estimated genetic advance was calculated to be 6.25 to 29.20. Heritability and genetic advance generally agreed in showing characters for which selection in the F2 would lead to substan- tial improvement. Excluding Families I, III, and IV because of pos- sible biased results from low progeny recovery, a preponderance of dominance gene effects coupled with low heritability estimates and genetic advance obtained in Family II, suggest that selection for this character should be slow. 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