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Reproductive morphology and genetics of Carica papaya (L.)
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|Title:||Reproductive morphology and genetics of Carica papaya (L.)|
|Authors:||Arkle, Thomas Dudley|
|Abstract:||This study was undertaken to examine the effects of climate and inheritance on carpellody and sterility in Carica papaya (L.). Sex in papaya is determined by a triple allelic series, "M1m", "M2m", and "mm", representing males, hermaphrodites and females, respectively. All combinations of the dominants are lethal. The hermaphrodite may tend toward femaleness (carpellody) or toward maleness (female sterility). Genetics for the factors carpellody and sterility have not been determined but it has been proposed that 2 different sets of factors are responsible. Changes in temperature and rainfall are known to influence the sexual expression of hermaphroditic plants but their specific degree of influence on several different known sexual forms of hermaphroditic plants have not been reported. Information about the climatic influences on sexuality in papaya will be useful in improving the commercial crop through breeding methods designed to minimize the effects of sexual changes. Three inbred hermaphroditic lines selected for highly stable expression of high carpellody, high sterility, and mostly normal elongata flowers were used. Studies of floral initiation and development indicated that floral primordia were laid down 7 to 10 weeks prior to anthesis at the rate of about one new bud every 3 days. Differentiation of stamens began 7 to 8 weeks prior to anthesis and was completed by 5 weeks before anthesis. Ovaries began differentiating 6 to 7 weeks prior to anthesis and were complete by 4 weeks before anthesis. The 3 inbred lines and their crosses (F1 , F2, BC) were planted in S randomized incomplete blocks at Malama-Ki on the island of Hawaii. Sexual changes of all plants in the orchard were correlated to temperature and rainfall changes from 4 to 10 weeks prior to anthesis for a period of 1 year. Results indicated that sex response to climatic influence was greatest at about 7 to 8 weeks prior to anthesis. Variations in sex expression from strongly carpellodic to strongly female sterile in the hermaphroditic trees were categorized into 7 "magnitudes" of expression. Trees were placed into one of these magnitudes in accordance with the sex expression of the last open flower each week and then placed into "classes" based on the overall yearly sex expression pattern of the tree. Results indicated that plants of the highly stable parents required as much as a 5°F. change in temperature before a shift in sex expression occurred. Plants with sex expressions lying between the parental types required smaller temperature changes for sexual shifts to occur. The response to changes in temperature appeared to be additive. The segregation patterns of carpellody and sterility are also presented. The inheritance appears to be quantitative with partial dominance of carpellody. A genetic model is presented which utilizes a basic tri-hybrid ratio with 2 factors for carpellody (c/c, c/c) and 1 for sterility (s/s) and their normal alleles (+). "s" alleles were found to be epistatic over c alleles when "c" alleles were heterozygous. However, if "c" alleles were homozygous, carpellody would be exhibited regardless of "s". Expected and observed ratios were compared on this basis and chi-square indicated a close fit.|
Thesis (Ph. D.)--University of Hawaii at Manoa, 1973.
Bibliography: leaves -116.
x, 116 l illus., tables
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|Appears in Collections:||Ph.D. - Horticulture|
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