GENETIC DIVERSITY IN EASTERN US SOFT WINTER-WHEAT (TRITICUM-AESTIVUM L EM THELL) BASED ON RFLP AND COEFFICIENTS OF PARENTAGE

Genetic diversity in a set of 11 red and 11 white wheat lines from the Eastern U.S. soft wheat germplasm pool was measured using restriction fragment length polymorphism (RFLP) assay and coefficients of parenta ge (COP) analysis. On average, 78% of all bands revealed by three enzy mes with 48 RFLP clones were monomorphic. Average pairwise genetic sim ilarity (CS) was 0.97 when data from all enzymes were pooled. Probe Po lymorphic Information Content (PIG) indexes ranged from 0 to 0.73 with a mean of 0.2. Fewer than 55% of the probes revealed any polymorphism . The frequency of polymorphism in the Eastern U.S. soft white winter (SWW) wheat gene pool was much lower than that observed in the Eastern U.S. soft red winter (SRW) wheat gene pool. SWW lines formed a single group on a dendrogram based on cluster analysis of RFLP-derived GS es timates, while SRW lines did not form a single group. COP values for a ll pairs of the Eastern U.S. soft wheat lines ranged from 0.02 to 0.9 with a mean of 0.21. SWW wheat lines traced to 53 ancestral lines and had an average COP of 0.51. The SRW wheat gene pool had more complex p arentages (mean COP = 0.15 and a total of 65 ancestral lines). COPs we re correlated with RFLP-based GS for all line pairs (r = 0.73, P < 0.0 1). However, correlations between the two similarity measures were sub stantially lower when the SRW and SWW wheat gene pools were considered individually (r values of 0.23 and 0.28, respectively). The actual GS among unrelated lines in the U.S. Eastern soft wheat gene pool appear s to be higher than that observed for unrelated landraces from Southwe st Asia (0.96 vs. 0.905), suggesting that the ancestral landrace paren ts of this gene pool were themselves drawn from a base population wher e inbreeding, i.e., F, was greater than zero.