. in. .2... . ‘ v s r hr. '9 ~£O:;x V c F?! fife. VD! F 5‘ V ngf I s. ' ‘f’tf.:‘b .. it b V! VWP.‘ 5’; l our?! 0' c ittfvsv. vi fitif f ~0t1¢§k 5 It. I. g’. f I f . r) . . fluffy... ”Viki? .gty {1%.fr..ltlthc.r .909!!! fig; Q. , \ In .1». “it .I tr. . . {.ggv‘lbihrvl. v ergo: .vrfiht.‘ t . fl 0... 3A.. ) . . ‘I‘ilfil‘f , ‘ VIBPI, f‘ttf‘ I lull”: PI!HJIU’-J§.Wnflflif.§€ to o .r ti . ‘ ‘ Ail £5, E 1 iv . ff‘ftr(£.£‘ fig... . ‘hfibflmflwfi . 55:: Itiffffggv {It gt»... ego. Shir: ii... .. .. “1;: “ £4... . vzrg.;)hwflh? , ‘ ‘flfttvg . bf? ”F? l. R‘f'un; t gfifriif . ‘95.! "f;f§L}£tgfi\f§f§ 8454:1159! ”(iflhvlrhafllwfolftvunhnltl ..r..¥'b.ra.,x)£t If}, .. 125.33” :Kt 14¢?er . rt . .r LIBRARY Michigan State University This is to certify that the thesis entitled A DIALLEL ANALYSIS OF BOLT RESISTANT GERMPLASM IN SEVERAL BRASSICA SPECIES AND THE INHERITANCE 0F LATERAL SUPPRESSION AND LEAF NUMBER IN BROCCOLI (Brassigg oleracea L. gtalica group) M ed y Katherine A. Keyes has been accepted towards fulfillment of the requirements for Masters , Horticulture degree in a Major professor [hue September 4, 1987 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution MSU LIBRARIES m \— RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. A DIALLEL ANALYSIS OF BOLT RESISTANT GERMPLASM IN SEVERAL BRASSICA SPECIES AND THE INHERITANCE OF LATERAL SUPPRESSION AND LEAF NUMBER IN BROCCOLI (Brassica oleracea L. Italica group) By Katherine A. Keyes A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture I987 ABSTRACT A DIALLEL ANALYSIS OF BOLT RESISTANT GERMPLASM IN SEVERAL BRASSICA SPECIES AND THE INHERITANCE 0F LATERAL SUPPRESSION AND LEAF NUMBER IN BROCCOLI (Brassica oleracea L. Italica group) BY Katherine A. Keyes A combining ability analysis for bolting response was performed on data from an incomplete diallel cross among 12 parents representing seven species. Significance for all contrasts and effects was observed. Results suggest diversity among parents and that bolt resistance will respond to selection. The Hakuran group was found to contribute the greatest amount of bolt resistance to its progeny. Studies were conducted to determine the inheritance of lateral suppression and leaf number in broccoli. In reciprocal crosses 83-857-2 x "Spartan Early" lateral suppression was found to be dominant over non-suppression. A 9:? recessive suppressor model is proposed. Correlation studies suggest no relationship between lateral suppression and other characters studied. F data from the cross between 83-866-1 x "Spartan Early"2 showed that leaf number was controlled by one or two major loci and modifiers, with few leaves being dominant over many leaves. To my parents, Janet (in memory) and Norman Keyes, for their love and support all through my life. ii ACKNOWLEDGEMENTS I would like to express my thanks and appreciation to Dr. S. Honma for his help and guidance during my graduate career and in preparation of this manuscript. I would also like to thank the members of my guidance committee, Dr. M.W. Adams and Dr. T. Islieb for their help and advise. Many thanks to Gary Winchell, Lou Pollack, and Bill Priest for help in planting and maintaining my field plots. Finally, I wish to express sincere gratitude to the friends who helped in taking field data, especially to Michael McCaffery for his friendship, encouragement and help during my time in graduate school. iii TABLE OF CONTENTS Page LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . vi LIST OF FIGURES. O O O O O O O O O O O O O O O O O O O O Vii PART I: A diallel analysis of bolt resistant germplasm in several Brassica species. INTRODUCTION 0 O O O O O 0 O O O O O O 0 O O O O O 1 LITERATURE REVIEW . . . . . . . . . . . . . . . . . 3 MATERIALS AND METHODS . . . . . . . . . . . . . . . 10 Parent Material . . . . . . . . . . . . . . . . 10 Vernalization Procedure . . . . . . . . . . . . . 12 Screening Parent Material . . . . . . . . . . . . 13 Hybridization . . . . . . . . . . . . . . . . 15 Vernalization Experiment . . . . . . . . . . . . .15 Data Analysis . . . . . . . . . . . . . . . . . . 18 RESULTS AND DISCUSSION . . . . . . . . . . . . . . . 27 SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . 35 LIST OF REFERENCES . . . . . . . . . . . . . . . . . 36 PART II: Inheritance of lateral suppression and leaf number in broccoli (Brassica oleracea L. Italica group). INTRODUCTION . . . . . . . . . . . . . . . . . . . . 4O LITERATURE REVIEW . . . . . . . . . . . . . . . . . 42 MATERIALS AND METHODS . . . . . . . . . . . . . . . 48 Parent Material . . . . . . . . . . . . . . . . . 48 Hybridization . . . . . . . . . . . . . . . . . . 49 Field Experiment . . . . . . . . . . . . . . . . 50 Data . . . . . . . . . . . . 51 Data Analysis- Axillary Shoots . . . . . . . . . 51 Data Analysis- Leaf Number . . . . . . . . . . . 51 RESULTS AND DISCUSSION . . . . . . . . . . . . . . . 53 Shoots . . . . . . . . . . . . . . . . . . . . . 53 Correlations . . . . . . . . . . . . . . . . . . 57 Leaf Number . . . . . . . . . . . . . . . . . . . 57 SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . 62 iv Shoots . . Leaf Number . . LIST OF REFERENCES APPENDIX . . O 62 63 64 67 LIST OF TABLES PART I Table Page 1. Parental lines used in diallel study . . . . . . . 14 2. Vernalization treatments for parents and F1 progeny . . . . . . . . . . . . . . . . . . . . . 19,20 3. Explanation of contrasts in diallel model . . . . 26 4. Minimum vernalization requirements of parents and F progeny . . . . . . . . . . . . . . . . . . . . 28 1 5. Variance analysis of parental and combining ability effects . . . . . . . . . . . . . . . . . . . . . 29 6. Mean separation test for minimum vernalization requirements among parental species. . . . . . . . 31 7. Estimates of individual effects . . . . . . . . . 32 A-1. Estimates of individual SCA effects for bolt resistance . . . . . . . . . . . . . . . . . . . 67 PART II 1. Chi-square test for goodness of fit for pooled reciprocal crosses of “Spartan Early" x 83-857-1, based on a two gene, 9:? segregation ratio for lateral suppression . . . . . . . . . . . . . . . 53 2. Frequency distribution of leaf number for the cross 83-866—1 x "Spartan Early" . . . . . . . . . 58 3. Chi-square test for goodness of fit for the cross 83-866—1 x "Spartan Early", based on the observed 90:22 segregation ratio for leaf number. . . . . . 59 vi LIST OF FIGURES PART I Figure Page 1. Seed yield of crosses obtained in the incomplete diallel cross . . . . . . . . . . . . . . . . . . 17 2. Stages in seedstalk development . . . . . . . . . 22 PART II 1. Broccoli stalks with leaves removed . . . . . . . 55 2. Frequency curves for leaf number in broccoli cross 83-866-1 x "Spartan Early" . . . . . . . . . 61 vii PART I: A DIALLEL ANALYSIS OF BOLT RESISTANT GERMPLASM IN SEVERAL BRASSICA SPECIES INTRODUCTION Brassica species, like many biennial plants, require vernalization in order to flower. Vernalization induces the change from the vegetative to the reproductive phase in response to low temperatures. The length of cold period required varies among species and between cultivars. As Chinese cabbage (Brassica campestris L. Pekinensis group) becomes more popular in the western world, a longer production season is desirable. At present, Chinese cabbage is grown as a late summer crop because cool spring temperatures cause premature flowerstalk formation (bolting) which makes the crop unmarketable. Cultural practices, such as use of protective row covers and adjustment of planting dates may be employed to reduce losses due to bolting. Row covers are costly in terms of time, labor, and capital. A more permanent and satisfactory solution to the problem is the development of bolt-resistant cultivars. Thus the production season could be extended into early summer. Other Brassica species are known to have slower bolting characteristics, that is a longer vernalization requirement. Since other traits, -such as disease resistance, have been transferred through interspecific hybridization, it is possible that genes for bolting resistance could be transferred to commercial Chinese cabbage cultivars. The objective of this study was to examine several Brassica l species and progeny of interspecific crosses to determine their vernalization requirements for possible use as sources of bolt resistance in addition to those already reported. LITERATURE REVIEW Vernalization Many biennial plant species have an obligate cold requirement in order to flower. The length of cold period varies among species and between cultivars. This phenomenon, called vernalization, induces the change from vegetative to reproductive growth in response to low temperatures Gassner (cited by Purvis, 29) was the first to examine low temperature effects on the promotion of flowering of winter cereals in 1918. Other crops requiring vernalization are celery, beets, and members of the genus Brassica. This literature review will focus on vernalization aspects of Brassica species, in particular Chinese cabbage (g; campestris L. Pekinensis group). A distinction must be made between regular flowering in response to vernalization and bolting, the latter being commonly referred to as premature flower stalk formation. In Chinese cabbage, "bolting" refers to the formation of a flower stalk before a marketable head is produced. Other closely related Brassica species have "later bolting" characteristics. The effectiveness of the low temperature treatment depends on temperature, the length of exposure, and the age or size of the plant at the time of flowering (5,9,35). Some investigators have studied the interaction of photoperiod and low temperature on flowering. Each of these catagories will be discussed in detail. 4 The exact physiological effects of vernalization are not known, but two schools of thought have emerged. The first is that the vernalization treatment, per se, does not induce flowering, but only sensitizes the plant to the appropriate daylength and/or temperature conditions (29). After vernalization, no flower primordia are formed, but the plant is "ripe to flower"-- that is all the prerequisites to flowering have occurred but the last step (24,38). Exposure to low temperatures hastens the capacity to flower, but shows up as an after effect. It is only a preparatory phase, not a true inductive effect (3). The other school of thought is that the period of cold temperatures is an inductive process, and the subsequent environmental conditions only hasten or delay flower stalk development. This occurred in cabbage plants (g; oleracea L. Capitata group) (21), and in recent experiments with Chinese cabbage (7,37). Numerous investigators have tried to determine the interaction of photoperiod and the vernalization treatment. Chroboczek (4) confirmed that table beets (ggtg vulgaris) are "long day plants" (L.D.) by shortening the time for seed stalk formation by artificially extending the daylight following vernalization. A combination of low temperatures (10-15 C) and long days (15+ hrs.) is most effective in obtaining a high seed yield in beet. He also noted that beets respond better to the cold treatment when they are lighted than if they are in darkness (5). S Lorenz (16) reported that Chinese cabbage flowered more rapidly under a 16 hr. day than an 8 hr. day. Short day length appears to have a negative effect on flowering because it remained vegetative longest when grown under short daYs (8 hrs. light) with relatively high temperatures (above 24 C) (14,16). Premature bolting and flowering in Chinese cabbage was delayed or prevented when plants were raised under S.D. (10 hrs.) for 3-4 weeks before transplanting into natural long days (18 hrs.) (22). However, Vander Meer and Van Dam showed that daylength had limited influence on Chinese cabbage compared to low temperatures and genotype (1,37). Similarly, Elers and Wiebe (7) found that with constant low temperatures, no photoperiodic effect was noticable in Chinese cabbage. They concluded that Chinese cabbage requires cold for flower initiation, and long days stabilize the vernalization effects. As stated previously, the effect of photoperiod can only be studied in relation to temperature and the duration of vernalization. Response to these factors has been studied in many cold-requiring plants. In table beets, plants held at 4.4 C to 10 C for 30 days induced flowering (under long days) (5). The most effective condition to induce bolting in celery is 2 weeks or more at 15.5 C or lower (34). Collard (Brassica oleracea Acephala group) cv. "Vates" has similar requirements of 5 weeks at 6 C for floral induction (26). Lorenz observed the most rapid flowering of Chinese cabbage occurs when plants are held at 5 C for 2 weeks under long days, and followed by warmer temperatures. It is generally agreed that, depending on the temperature, the longer the plants are exposed to cold, the faster they flower (2,4,6,11,14,23,26,36,42). Yamasaki (42) developed a general formula to predict flowering in Chinese cabbage: (13 C-X)Y = 87 C, where X is the temperature below 13 C, and Y is the number of days with minimum temperature below 13 C. When the sum of the equation equals or exceeds 87 C, bolting will occur. Sensitivity to low temperature varies widely among cultivars (9,10,23). High temperatures immediately following the cold period may nullify the effects or "devernalize" the plants. For example, temperatures of 21-27 C prevented table beets from flowering (4,5). If Chinese cabbage and Japanese radish (Raphanus sativus L. var. acanthiformis Makino) are not fully vernalized, they will not complete the successive stages of floral initiation (6). Purvis and Gregory (30) found that discontinuous low temperature treatments on winter rye elicited less response than continuous exposure, with the same total time exposed. This was shown only with short individual periods at low and high temperature. Plants are more stable to heat exposure the longer they are vernalized. After 8 weeks of cold, high temperatures (35 C) did not have a devernalizing effect. The apical meristem is the site of perception of the cold treatment for most vernalization-requiring plants. Chroboczek (4) demonstrated, that by cooling beet meristems with cold water through a rubber tubing wound around the growing point he could induce flowering. Wellensiek (40), in Lunaris biennis, concluded that vernalization took place only where there is actively dividing tissue (mitoses). Purvis also regenerated fragments of winter rye embryos that contained the shoot apex (28). Another factor to consider in the vernalization effects is the stage of the plant that is sensitive to cold treatment. Chroboczek (5), in a study on table beets, concluded that it was the age, not the size of the plant, that determines susceptibility to cold temperatures. Species such as Chinese cabbage, Japanese radish and Brassica ngpgg may be vernalized as germinating seeds (7,23,31). Eguchi et al. (6), found that 60- day-old seedlings of Chinese cabbage were more sensitive to the chilling temperatures than 2-day- old seedlings. Flower stalk development and flowering were accelerated by low temperatures in older seedlings as compared to young ones. However, Guttormsen and Moe (9) found that increased plant age (1-3 weeks) at the start of vernalization delayed bolting in certain cultivars. Other species such as table beets, cabbage, and collards must be vernalized at the "green-plant stage" or after they have completed a juvenile phase (37,38). Collard cv. "Vates" must reach a stem diameter of 4.0 mm to be sensitive to low temperatures (2). Cabbage plants must attain a certain size before they will bolt (21). Genotype also plays a role in the premature seeding of beets and other biennials, but the environment determines whether the bolting factors will be expressed. Two plants of the same cultivar may respond differently under different environmental conditions. It is impossible to determine the mode of inheritance of bolt resistance without consideration of the environmental conditions (5). Purvis asserted that in cold requiring plants, the vernalization treatment is a physiological compensation for the absence of "flowering genes" (29). The number and action of the genes involved varies for the species in question. In Petkus rye (Secale cereale L.), the difference between winter and summer types is conditioned by one major gene, with the winter habit being recessive. It is possible to have a population of either habit through the selection of the desirable genotype (24). Van Heel determined that bolting in sugar beets (Beta vulgaris L.) is recessive (36). Bouwkamp and Honma found easy-bolting in celery (Apigm graveolens Dulce group) to be dominant to later-bolting, and the response was controlled by one major gene (13) (1). The tendency of cabbage to bolt is recessive (33). In an intraspecific cross of Chinese cabbage X turnip, bolting appeared to be controlled by 2 major additive genes. There is an apparent association between bolting response and the turnip phenotype (20). Similarly, results of an interspecific cross between kale and Chinese cabbage suggest that a few major additive genes condition bolting response (18). Bolting in Chinese cabbage appears to be controlled by 4‘ major additive genes with modifiers controlling the degree of resistance (19). "LB-7", a hybrid between Chinese cabbage and kale, has the genotype 2 y y y and bolts after 3 weeks 1 1 2 2 of vernalization (19). MATERIALS AND METHODS Parent Material Chinese cabbage Chinese cabbage (Brassica campestris L. Pekinensis group) is a head forming vegetable with a biennial habit. The foliage is light green in color. Its large leaves are tender and veiny with wide petioles and undulating margins. Two cultivars were used in this study, " Wong Bok" and "Mandarin". Wong Bok forms a short barrel shaped head and is a late season standard cultivar. Seed was obtained from Takii Seed Co., Kyoto, Japan. Mandarin, a small headed, early summer variety was obtained from the National Seed Storage Laboratory, Fort Collins, CO. Both cultivars bolted after 2 weeks of vernalization. Turnip Rape Brassica napus Oliefera L.F.F. Fibie group cv. "Siberian" is a winterhardy biennial. It is a leafy plant with blue-green coarse foliage with dentate margins. Seeds were obtained from the Institute of Plant Genetics, Warsaw, Poland. Siberian turnip rape has a vernalization requirement of at least 6 weeks. Pak choi Pak choi or Bok choy (Brassica campestris L; Chinensis group) is a leafy non-heading biennial. It has large leaves with wide petioles, prominent veins and smooth margins. 1. 1. This cultivar "Su-e-ma" (translated "Later of April"), was obtained from Guan Zhong Yang from the Peoples Republic of China. It can be induced to bolt after 3 weeks of 5 C temperatures. Chikale The line "LB-7" is a late bolting line which was developed from an F population derived from an interspecific cross between Sibgrian kale (Brassica ggpgg) and Chinese cabbage cv. Mandarin . This cross was first made by Honma and Heecht (12) and further selected by Mero and Honma (19). The foliage has a shape intermediate between Chinese cabbage and kale, but is more similar to Chinese cabbage in texture and color and does form a head. LB-7 is reported to bolt after 4 weeks of vernalization (19). Stubble turnip "Taronda Zelder", a tetraploid variety of stubble turnip (B; campestris Rapa group) was obtained from the Institute for Horticultural Plant Breeding, Wageningen, The Netherlands. The root of Taronda Zelder is I small, cylindrical and purple. The leaves are dark green, narrow and coarse with wavy margins. This cold hardy plant is used for fodder in other parts of the world. Its vernalization requirement is 4 weeks. Hakuran Hakuran is an artificially synthesized g; napus (25,42). 12 It is an amphidiploid developed from an interspecific cross between Chinese cabbage and cabbage (g; oleracea) which showed heading characteristics. According to Yamagishi and Takayanagi (42), Hakuran can be easily crossed with Chinese cabbage and may be useful as a bridge species in other Brassica vegetables. The foliage is medium green in color. Its texture is intermediate between Chinese cabbage and cabbage, more coarse than Chinese cabbage, but not as waxy as cabbage. Leaves are semi-rugose and have semi-undulate margins. Tyfon Tyfon is a synthesized variety developed from a cross between stubble turnip (g; raga) and Chinese cabbage (B; campestris Pekinensis group). It is currently grown as a fodder crop and also as greens in the 0.8. (41). The foliage is medium green in color and has coarse texture resembling the turnip. The large leaves have serrate margins and long, thin petioles. It is comparable to rape and stubble turnip for cold hardiness. Seeds were obtained from the Pacific Seed Production Co., Albany, OR. Vernalization Procedure All vernalizations in this study were conducted in a vernalization room held at 5 C :1. Plants were exposed to 12 hours of light/day with banks of fluorescent lamps (approximately 20 Wm ). Upon removal from the cooler, plants were kept in a 20 C greenhouse with 14 hours of light/day supplied by G.E. High Intensity Discharge lamps with 1000 watt multivapor bulbs (approximately 24 Wm-z). Yamasaki (43) proposed a formula for predicting floral induction of Chinese cabbage, where 13 C is the critical temperature: (13 C ~X)Y a 87 C, where x is the temperature below 13 C and Y is the number of days with minimum temperature below 13 C. When the sum of the equation is greater than or equal to 87 C, flowering is induced. This formula proved to be adequate under the vernalization procedures previously described since Mandarin and Wong Bok did not bolt after 1 week, but did bolt after 2 weeks at 5 C in the vernalization room. Following Yamasaki's formula, 1 week of vernalizaton only adds to 56 C which is insufficient to induce bolting, but 2 weeks at 5 C equals 112 C which is sufficient to induce flowering. Screening Parental Material In November 1983, 4 week old seedlings of 18 potential parent lines were planted in a greenhouse ground bed. The bed was fertilized prior to planting with .013 kg/m2 of ammonium nitrate and .065 kg/m2 of sulfur. Based on observations of phenotypic desirability and uniformity, 12 parental lines representing 7 species and species hybrids were selected to be used as parents in a diallel study (Table 1). On February 15,1984, 2 plants from each selected parental line were transplanted into large pots and vernalized for 6 weeks to obtain selfed seed to be used 14 Table 1. Parental lines used in diallel study 535:2: Cultivar Species l Siberian Turnip rape 2 Tyfon (Chinese cabbage x Stubble Turnip) 3 Hakuran (Takii Seed) (Chinese cabbage x cabbage) 4 Taronda Zelder Stubble Turnip 5 Hakuran (Mikado Seed) (Chinese cabbage x cabbage 6 Hakuran Strain ”20 Self" u 7 Hakuran Strain ”36 Self" u 8 Hakuran Strain ”43 Self“ " 9 Mandarin Chinese cabbage lO LB-7 (Chinese cabbage x Kale) ll Su-e-ma Pak-Choi l2 Wong Bok ' Chinese cabbage 15 in future experiments. In the spring of 1984, a preliminary experiment was conducted to determine the vernalization requirements for the 12 parental lines. The treatments were 1,2,3,4,5,6 weeks of cold treatment at 5 C. None of the parental lines bolted after 1 week of vernalization. Siberian rape (2) required at least 6 weeks to bolt, the Chinese cabbage lines 9 (Mandarin) and 12 (Wong Bok) bolted after 2 weeks of cold and the rest were intermediate. Due to poor germination, the parental lines 4 ("Taranda Zelder") and 8 (Hakuran Strain 43) were not included in this phase of the study. Hybridization Crosses were made during the fall and winter of 1984-85. Pollinations were made by emasculating the buds, brushing pollen of the male parent on the stigmatic surface of the female parent, then covering with glassine bags until the siliques began to develop. Many of the crosses failed to produce viable seed after numerous pollinations (Figure 1), probably due to incompatibility and differences in chromosome number. Due to the many unsuccessful crosses, the design became an incomplete diallel. Vernalizaton Experiment The F progeny were planted in vermiculite at planned intervals beginning September 6, 1985. They were transplanted 7-10 days later into No. 24 PVC trays filled with a mixture Figure l. Seed yield of crosses obtained in the incomplete diallel cross. l7 00 0% O... or ON mm 38 om 0+. 00 +8. ON +8. $8. Om. ON on mm mm on or ON we. on ON 9v 0% mm rm 0—. ON F P ON mm or on mp on mm mm N. xom 803 :. Optimism 0— film: m .962 Savage: 83.5%: 88.5%: szc:on ._oN c8. 29...:on :83 Nppwormwhmmsnm F v—NP’DVLDCONQ esteem 18 of equal parts of peat, perlite, and vermiculite. The experiment was a completely randomized design with 3 replications. There was a maximum of 72 plants of each line. Standard cultural practices for Chinese cabbage were employed. Vernalization treatments for most of the F 's were estimated based on the cold requirements of the suiceptible parent, the mid-parent value, and 1 week beyond the bolt resistant parent. For F 's with few seeds (less than 20) only the mid-parent treatmeht was used (Table 2). All treatments were removed from the vernalization room on November 15, 1985 and placed in a greenhouse to observe bolting response. The greenhouse temperature was kept at 15.5 C for 2 weeks to stabilize the plants and to prevent devernalization, and subsequently raised to 20 C for the remainder of the experiment. Supplemental lighting of 14 hours/day was provided by HID lamps. Data on the number of bolted plants was recorded every 2—3 days for 6 weeks beginning December 2,1985. Plants were considered to have bolted when flower buds were visible in the apex (17). At the conclusion of the experiment, all remaining plants were cut in half longitudinally to determine if the apex had begun to elongate, but not yet shown visible bud (Figure 2). An elongated apex indicates floral induction according to the criteria defined by Mero and Honma (17). 2353 Analysis 19 TABLE 2 Vernalization treatments selected for parents and hybrids Pedigree No. Weeks at 5 C (female, male) 0 2 21/2 3 31/2 4 41/2 5 6 1 1 x x x 2 2 x x x x x x x 2 4 x 3 3 x x x x x 3 5 x 3 9 x 3 10 x 3 11 x 3 12 x 4 2 x 4 4 x x x x x 5 1 x 5 4 x 5 5 x x x x x 5 6 x x 5 7 x x 5 8 x x 5 9 x 5 11 x x 5 12 x 6 6 x x x x x 7 7 x x x x x 8 8 x x x x 9 1 x x x x 9 3 x 9 4 x 9 5 x 9 6 x 9 7 x 9 9 x x x x x x 10 1 x x x 10 3 x 10 7 x 10 9 x x 10 10 x x x x x x x 20 TABLE 2 (cont'd) Pedigree Weeks at 5 C (female, male) 0 2 21/2 3 31/2 4 41/2 5 6 10 11 x x 10 12 x x 11 3 11 4 11 5 11 6 7 8 9 :4 xx x 11 11 11 11 10 11 11 x x x 11 12 x 12 9 x x x 12 12 x x x K x x>cxacx Nifi 2¢X>¢xiflx 9‘“ 3 .50) and therefore only tie pooled data are shown. The frequency distributions for all generations are presented in Table 2. Since the F distribution is skewed toward low leaf number and its meanzis close to that of the low leaf number parent, there appears to be dominance toward low leaf number. The F was partitioned into low and high leaf number between 18 an: 19 leaves. This dividing point is the arithmetic mean between the two parents. With this class as the separation point between the two phenotypes, the 90 low leaf : 22 high leaf ratio conformed to either a 3:1, 13:3, or 12:4 8 amodm m. mwmncmznk aimnsiaeeloz em Emma sesame 461 firm owomm mwummmud x zmumwnmz mmxdk= 88328 .6. ca. : a a z a a z a G mo N. .5 B E mm a :8: v.9:nm areas... a . - 1 - . - - - . 2383.: c: 33% m2: 3 . - a m V m N a N _ i - - I . 5.3:.2 ea mam... 1822.5 . - m 3 5 mm s z : m a 1 . 3.33 3.8 Ammv mmwdk 59 segregation pattern (Figure 2). The Chi-square test shows a good fit to these models (Table 3). TABLE 3. CHI-SQUARE TEST FOR GOODNESS OF FIT FOR THE CROSS 83-866-1 X "SPARTAN EARLY" BASED ON THE OBSERVED 90:22 SEGREGATION RATIO FOR LEAF NUMBER Generation Genetic Theoretical Chi-sq. P model ratio Pooled F2 3 : 1 84 : 28 1.440 .25-.10 13 : 3 91 : 21 0.015 .95-.90 12 : 4 84 : 28 1.440 .25-.10 In this cross the following hypothesis is proposed: One or two major genes with heterozygous modifiers determine leaf number. Studies in several Brassica species support the hypothesis of dominance for few leaf number which is controlled by a small number of genes. Summers and Honma (26) observed dominance for few non-wrapper leaves in crosses between two smooth green leafed cabbages. Chauhan and Singh (6) concluded the number of leaves in Indian mustard (pp juncea L. Czern and Coss.) was governed mainly by dominance effects and possibly overdominance. Inheritance of leaf number in spring rape (pp ppppp L.) appeared to be determined by one or a small number of major genes (30). 60 Figure 2. Frequency curves for leaf number in the broccoli cross 83-866-l x Spartan Early. N 0 Frequency E3 61 O AlllllllllllLlll “3T [ 14 I T r—I I I I‘l I I I 18 22 Leaf Number 26 SUMMARY AND CONCLUSIONS Shoots Data from the pooled F populations between 83-857 and "Spartan Early" were examined to determine the mode of inheritance of lateral suppression character. Dominance for lateral suppression was noted. A model of two epistatic genes was proposed where P ("Spartan Early") is designated as Np Np Np Np and parint (83-857) is designated as 1 1 2 2 BE 22 BE 22 - 1 1 2 2 Inability to obtain sufficient backcross populations was due to the short flowering period of the lateral suppressor parent since the absence of secondary shoots did not provide flowers to make backcross pollinations. Estimates of heritability and genetic advance were not calculated since backcross data were not available. Tucker (31) suggested that inhibition of axillary bud formation in lateral suppressor type tomato plants may be due to an accumulation of indole acetic acid which suppresses bud and shoot development. The inhibition may be controlled by the levels of abscissic acid and cytokinin since lateral suppressor tomatoes had lower levels of these hormones than normal plants. Perhaps if the hormone levels of each plant in this experiment could have been measured, there may be evidence to support this hypothesis. It is possible that the two gene system to control lateral suppression in broccoli may be part 62 63 of a more complex biochemical mechanism. Leaf Number Leaf number was found to be controlled by one or two major epistatic genes and modifiers. Dominance was noted for few leaves. Ratios obtained by partitioning the F generation into the two phenotypes based on the arithmeti: mean of the two parents conformed to a 3:1, 13:3, or 12:4 ratio. Estimates of heritability and expected gain from selection were not calculated due to the absence of the backcross generations. LIST OF REFERENCES 10. 11. 12. 13. 14. REFERENCES Akratanakul, W. and J.R. Baggett. 1977. The inheritance of axillary heading tendency in cabbage, Brassica oleracea L. (Capitata group). J. Amer. Soc. Hort. Sci. 102(1):5-7. Anstey, T.H. and J.F. Moore. 1954. Inheritance of glossy foliage and cream petals. J.Hered., 45:39-41. Bonaparte, E.E.N.A. 1977. Diallel analysis of leaf number and duration to midsilk in maize. Can. J. Burton, Glenn W. 1951. Quantitaive inheritance in pearl millet (Pennisetum glaucum). Agron. J., 43(9):409-417. Buck, P.A. 1956. Origin and taxonomy of broccoli. Econ. Chauhan, Y.S. and A.B. Singh. 1973. Heritability estimates and gene effects for some agronomic traits in Indian mustard (Brassica juncea L. Czern & Coss). Indian J. Agr. Sci., 43(2):191-194. Dangi,O.P. and R.S. Paroda. 1978. Gene action in forage sorghum. Indian J. 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Inheritance of some quantitative characters in cabbage. Indian J. Genet. 25(1):57-64. Takahashi, T. and F. Yazawa. 1968. Studies on the flower bud differentiation and development of Italian broccoli (Brassica oleracea L. var italica Plenk). J. Fac. Agr. Shinshu Univ. 5:1-9. (Japanese with English summary). Thurling, N. and L.D. Vijendra Das. 1979. Genetic control of the pre-anthesis development of spring rape (Brassica napus L.). I. Diallel analysis of variation in the field. Aust. J. Agric. Res. 30:251- 259. Tucker, D.J. 1976. Endogenous growth regulators in relation to side shoot development in the tomato. New Phytol. 77: 561-568. Yarnell, S.H. 1956. Cytogenetics of the vegetable crops. II. Crucifers. Bot. Rev. 22(2): 81-166. Yukihiro, F. and T. Hirose. 1978. Effects of plant growth regulators on lateral shoot branching of broccoli. Tech. Bull. Fac. Agr. Kagawa Univ. 29(62):225-234. ' APPENDIX 67 Table A-l. Estimates of individual SCA effects for bolt resistance Effect Estimate Effect Estimate SCA l 5 .0022l SCA 5 9 -.0l439 SCA 7 9 .05903** SCA 5 ll -.04690** SCA 5 8 -.00378 SCA 9 ll .06038** SCA 3 10 -.02171 SCA 6 9 .00392 SCA 5 6 .01807 SCA l0 ll -.07749** SCA 3 5 .0287l SCA l 9 -.00955 SCA 3 9 -;01877 SCA 7 l0 -.07963** SCA 5 7 .00651 SCA 4 9 —.04449* SCA 3 ll -.0ll34 SCA 9 l0 .Oll85 SCA 4 5 -,03273 * SCA ** = Specific combining ability (female, male) , * = Significant at the l% and 5% level respectively. llllllll 071 4202 l 1111!. lllllllfllllllll