Coefficient of Parentage and Cluster Analysis of North American Dry Bean Cultivars
- Phillip E. McClean ,
- James R. Myers and
- James J. Hammond
Archaeological, morphological, and biochemical data suggest that common bean (Phaseolus vulgaris L.) was domesticated separately in South America and Central America. Variation in seed size, shape, and color is common in both centers of domestication and has been maintained as market classes. Despite extensive global transport, market classes have remained distinct. Although variation has been measured in genotypes from the two centers of domestication, the inter- and intra-market class genetic diversity among North American dry bean cultivars is generally unknown. Estimating genetic diversity improves the assessment of potential vulnerability to disease epidemics and the design of experiments requiring diverse genotypes. One method of assessing genetic diversity, based on pedigrees, is the coefficient of parentage (r). Coefficient of parentage data can be used in cluster analysis to identify groups of related cultivars. This study used the coefficient of parentage ta determine the degree of relationship among 143 dry bean plant introductions, landraces, breeding lines, and cultivars, represent. ing the major market classes grown in North America. Using r-values, 16 clusters were found, with 13 cultivars unassigned to any cluster. Three major clusters, which corresponded to small (navy and black), medium (pinto, pink, great northern, and red Mexican), and large (kidney) seed size, were observed. Crossing among these major groups was rare, although more recombination had occurred between the large and medium-seed size groups than between any other combination of groups. In general, the medium-seed size group exhibited more recombination and greater variability than the small-seed group. Mean within cluster r-values suggest that intra-market class genetic diversity is narrow, but the genetic diversity among market classes is greater. Therefore, exploiting the diversity among market classes would broaden the genetic base of dry bean breeding populations.
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