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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #87537
Title: AGRONOMIC SIMILARITY AMONG ANCESTRAL COTTON CULTIVARS AND ITS IMPACT ON GENETIC DIVERSITY ESTIMATES OF MODERN CULTIVARS

Author
item VAN ESBROECK, G - NCSU, RALEIGH, NC
item BOWMAN, D - NCSU, RALEIGH, NC
item May Iii, Oscar
item CALHOUN, D - MAFES, STONEVILLE, MS

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Genetic diversity of cotton varieties ensures that an insect or disease outbreak cannot cause widespread yield loss. Estimates of genetic diversity may be based on pedigree records, similarity in performance, or molecular markers. Pedigree-derived estimates of genetic diversity are simple to calculate but require detailed pedigrees and certain genetic assumptions that may not always be realized. Present research attempts to refine estimates of genetic diversity based on pedigree records. Statistical procedures that simultaneously consider numerous variety performance characteristics were used to compute a composite estimate of genetic diversity. The composite estimate of cultivar genetic diversity indicated that cultivars are more closely related than would be predicted from pedigree records alone. However, the relative ranking of diversity among cultivars was similar between the simple pedigree-derived estimates and the composite estimate. Overall, this study affirms previous findings that certain cotton cultivars are highly related. To guard against all varieties being highly related, public breeding programs must continue to focus on development of genetically diverse germplasm and subsequent free exchange with private sector firms that develop the cotton varieties.

Technical Abstract: Accuracy of pedigree-derived estimates of genetic distance depends on the availability of breeding records and on the validity of a number of assumptions. Pedigree analysis applied to cotton cultivars indicates a wide genetic base. Objectives of this study were to assess the agronomic similarity of ancestral cotton cultivars to pedigree-derived coefficient of parentage (CP) estimates and to determine the impact of these estimates on the CP among recently developed cultivars. Twelve ancestral and two recently developed cultivars were grown at three locations during 1995 and evaluated for agronomic and fiber properties. Multivariate analysis was applied to agronomic and fiber properties to create similarity indices (s). There was little agreement between CP and s. Several of the ancestral cultivars developed from the earliest introductions into the USA were very similar to the most recent introductions from Mexico. This suggested that all original Mexican introductions were genetically very similar. Changing the assumptions in pedigree analysis to assume the original introductions were related by the average s among the ancestral cultivars (s=0.43) decreased the level of diversity in frequently grown modern cultivars from CP=0.16 to CP=0.51. The high degree of similarity among ancestral cultivars suggests that pedigree-derived genetic distance estimates have overestimated genetic diversity among today's cultivars but probably have not affected relative relationships.