Genetic diversity among soybean plant introductions and North American germplasm

Elite North American soybean [Glycine mar (L.) Merr.] germplasm derives from a limited number of ancestors. Knowledge of genetic diversity patterns in elite germplasm and plant introductions (PIs) is needed to diversity efficiently the elite gene pool. The objective of this research was to study diversity among five gene pools consisting of either ancestral lines (AN), elite lines from northern (NE) or southern (SE) U.S. production areas, and PIs with a northern or southern maturity. The relationship among the pools was evaluated by analysis of 53 restriction fragment length polymorphism (RFLP) loci and by coefficient of parentage (CP). Clustering of lines on the basis of RFLP data was generally consistent with their prior pool classification, though AN lines were dispersed. Greater diversity was noted within the NE than the SE gene pool. The ancestors Mandarin-Ottawa and PI257435 appeared to be major sources of diversity in the elite gene pool. Diversity among gene pools was primarily due to gene frequency differences and not from the presence or absence of unique alleles. Much of the pattern of diversity in the elite population can be explained by molecular diversity among a few major ancestors, the relationship of these ancestors to the elite lines, and the geographic origin of the ancestors. The correlation of CP and SMC estimates of genetic similarity was 0.61.. Selection or drift appeared to have influenced the correlation. The reported diversity pattern may be a guide for finding and incorporating new genes into elite North American soybean.