PEDIGREE ANALYSIS OF ELITE SOYBEAN LINES

The reported genetic diversity of North American soybean [Glycine mar (L.) Merr.] cultivars is low. Public and industry breeders have initia ted programs to expand the diversity. This paper assesses the impact o f diversification efforts on the extent and pattern of diversity among elite lines and estimates the impact of industry on diversity. Coeffi cient of parentage (CP) analyses were performed with 122 lines from th e northern and southern regions of the USA. The average CP was 0.173: this value was 0.233 among northern lines, 0.261 among southern lines, and 0.100 between lines from different regions. These values, and an analysis of the number of ancestors and their contribution of parentag e to the elite population, were similar to values in previous reports, thereby indicating that recent efforts of public and proprietary bree ders have had little impact on diversity among current elite lines. Mi nor differences in genetic diversity were noted between lines from pub lic or proprietary sources. Industry has affected diversity by introdu cing parentage from PI 257.435, and the development of 'A3127' has ser ved as a genetic bridge between regions. Cluster analysis distinctly s eparated northern lines from Maturity Group V and VI lines and suggest ed four clusters within each region. Principal component analyses inte rpreted the clusters as groups of lines with genetic similarity to rec ently developed parents that were used extensively to generate the eli te population. Genetic diversity within sind between regions could be exploited by crossing pairs of lines that have a low CP. The effective ness of this approach could be enhanced by using cluster patterns to a chieve a more thorough sampling of the genetic diversity.