Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/29/1999
Publication Date: 4/1/2000
Citation: BROWN GUEDIRA,G.L., THOMPSON,J.A., NELSON,R.L., WARBURTON,M.L., EVALUATION OF GENETIC DIVERSITY OF SOYBEAN INTRODUCTIONS AND NORTH AMERICANANCESTORS USING RAPD AND SSR MARKERS, CROP SCIENCE, 2000. Interpretive Summary: Soybean breeders have produced hundreds of improved varieties adapted to growing regions of North America. However, analysis of parentage of these varieties has determined that as few as 18 soybean varieties introduced from China and the Koreas are the source of 85% of all genes in North American material. This narrow genetic base may threaten the ability of breeders to sustain genetic improvement of the crop. The USDA soybean germplasm collection has more than 15,000 soybean accessions, most have not been used by plant breeders. In order to aid breeders in the selection of genetically diverse parents for development of breeding populations, a study was done to assess the relationship of 18 major ancestors of North American soybean varieties with 87 soybean introductions. These introductions have been used in an USDA-ARS germplasm enhancement program aimed at incorporating new sources of genetic variation for agronomic traits into soybean germplasm adapted to central Illinois. DNA markers (random amplified polymorphic and simple sequence repeat markers) were used in conjunction with clustering procedures to determine genetic distance between lines and to group genetically similar accessions. Genotypes were placed in eleven clusters based on a consensus of the different methods utilized. The most stable groupings were among ancestors that corresponded with known relationships based on pedigree and maturity. Several groups of plant introductions were distinct from the majority of the ancestors. These lines may be useful to breeders wanting to utilize genetically diverse introductions in soybean improvement.
Technical Abstract: The genetic base of soybean [Glycine max (L.) Merr.] cultivars developed for North America is very narrow. This research was conducted to assess the relationship of the 18 major ancestors of North American soybean germplasm identified by with 87 plant introductions (PIs) that have been used in USDA-ARS germplasm enhancement programs aimed at incorporating new sources of genetic variation into soybean breeding populations. Genetic distances (GD) among the 105 genotypes analyzed were calculated from 109 random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) markers. Two hierarchical clustering algorithms were combined with data resampling and multidimensional scaling (MDS) to evaluate relationships among the genotypes. Genetic distances ranged from 0.08 to 0.76, with a mean of 0.52. Genotypes were placed in eleven clusters based on a consensus of the different methods utilized. The stability of clusters varied, as determined by the co-occurrence values calculated from the resampling iterations. The most stable grouping were among ancestors that corresponded with known relationships based on pedigree and maturity. Distinct clusters of PIs were also identified. Whereas clustering of PIs did not correspond to geographic origin or maturity, known relationships of lines based on pedigree were confirmed. Several groups of PIs appear to be distinct from the majority of the ancestors. These genotypes may be useful to breeders wanting to utilize genetically diverse introductions in soybean improvement.