DISTANCE STATISTICS AND INTERPRETATION OF SOUTHERN STATES REGIONAL SOYBEAN TESTS

The failure of genotypes to respond similarly to different environment al conditions, genotype environment (GXE) interaction, is an important aspect of genotypic stability. The objectives of this paper were to d evelop distances based on concepts of genotypic stability and to inter pret regional soybean [Glycine mar (L.) Merr.] tests based on these di stances. Distances increased in relation to differential responses amo ng sites for two genotypes or among genotypes for two sites. They were designed to evaluate the importance of region of origin in determinin g genotypic responses, the similarity of selections arising from diffe rent breeding programs, and the comparability of sites in regional tes ting. Seed yields for the Uniform Soybean Trials, Southern States, Mat urity Groups V and VI, 1981-1991, were evaluated. Region of origin for genotypes did not have a major impact upon the nature of genotypic re sponses; however, genotypes from all regions showed less differential responses when tested at sites in the East Coast Region. The Group V s elections from the North Carolina, Maryland, and Virginia breeding pro grams were more similar than selections from other breeding programs. Group VI selections from the Missouri program responded differently to environments than Group VI selections from other programs. The Plymou th, NC, Clemson, SC, and Athens, GA, test sites had similar relative s eed yields among genotypes. A central belt of comparable sites extende d from Virginia, North Carolina, South Carolina, and northeast Georgia to the mid and upper Delta Region. A northern belt of comparable site s covered Delaware, Maryland, western Virginia, Kentucky, upper Delta, and southeastern Kansas. The Tennessee sites were intermediate to the se two belts. Sites in northwestern Georgia and northern Alabama and t he remaining sites in the southern tier of states gave heterogeneous g enotypic responses. Comparable sites that represent areas within this region were not found. Genotypes with unique local adaptations would b e required.