EVALUATION OF SOYBEAN RFLP MARKER DIVERSITY IN ADAPTED GERM PLASM

Soybean RFLP markers have been primarily developed and genetically mapped using wide crosses between exotic and adapted genotypes. We have screened 38 soybean lines at 128 RFLP marker loci primarily to characterize germ plasm structure but also to evaluate the utility of RFLP markers identified in unadapted populations. Of these DNA probes 70% detected RFLPs in this set of soybean lines with an average polymorphism index of 0.30. This means that only 1 out of 5 marker loci was informative between any particular pair of adapted soybean lines. The variance associated with the estimation of RFLP genetic distance (GD(R)) was determined, and the value obtained suggested that the use of more than 65-90 marker loci for germ plasm surveys will add little precision. Cluster analysis and principal coordinate analysis of the GD(R) matrix revealed the relative lack of diversity in adapted germ plasm. Within the cultivated lines, several lines adapted to Southern US maturity zones also appeared as a separate group. GD(R) data was compared to the genetic distance estimates obtained from pedigree analysis (GD(P)). These two measures were correlated with r=0.54 for all 38 lines, but the correlation increased to r=0.73 when only adapted lines were analyzed.