A biosystematic study of Cucurbita pepo /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1986.
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| Subjects: | |
| Online Access: | Link to ProQuest copy Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | This biosystematic study of Cucurbita pepo and closely-related taxa was conducted based on electrophoretic, morphological, and flowering data. Data were collected from over 150 commercial cultivars and Mexican accessions of C. pepo. 45 commercial cultivars and Mexican and Colombian accessions o f C. moschata. 25 commercial cultivars and Mexican accessions o f C. mixta. 12 populations of C. sororia from Mexico, 17 populations of C. texana from Texas, and 6 populations of texana-like plants from Alabama. Arkansas, and Illinois. Examination of allozymes was based on allelic variation at 12 loci representing 6 enzyme systems (GOT, IDH, MDH, PER, PGI, and PGM). Mean number of alleles, mean proportion of polymorphic loci, mean expected heterozygosity, and coefficients of genetic identity were among the statistics that were calculated. Relationships among and within taxa were examined via principal component and cluster analyses. These techniques were also used to explore morphological variation. Separate analyses were performed on measurement data collected from seeds, vegetative parts, and floral structures, and on a qualitative data set containing characters of the mature plant and fruit. Flowering data included the number of days from germination to anthesis of the first staminate and pistillate flowers, the ratio of male to female flowers, and an estimation of the number of flowers produced over an eight week period. All analyses indicated that a major subdivision exists within C. pepo. This may reflect an early geographical divergence within the species, or multiple origins of domestication. Cucurbita texana is closely allied to the subdivision that apparently experienced much of its early diversification in eastern U.S. The other subdivision, which exhibits closer ties to Mexico, is exclusively represented in that country today. Results of the analyses suggest that spontaneous populations of texana-like plants in states northeast of Texas may represent relicts of the wild species beyond its currently recognized distribution. This possibility is an important consideration in trying to resolve the origin(s) of the domesticate. The very close relationship between C. mixta and C. sororia parallels that of C. pepo and C. texana. Among the domesticates. C. mixta exhibits closer relationships with C. pepo and C. moschata than the latter do with each other. |
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| Item Description: | "Major subject: Botany." Typescript (photocopy). Vita. |
| Physical Description: | xiv, 224 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 143-151). |