To use, maintain and increase crop germplasm collections efficiently, it is important to assess the diversity of these collections. In this study, 1383 accessions of Chinese spring sowing soybean (Glycine max) were used for SSR analysis. In total, 1111 alleles were detected among these collections with an average number of alleles (NA) of 18.52 per locus. The genetic diversity index (PIC value) varied from 0.456 to 0.928 with an average of 0.815. Intensive breeding of cultivars have led to a decrease of genetic diversity. Random-repeated sampling within landraces of different geographical regions suggested that the ranking of both average NA and PIC values among different geographical regions were North spring soybean (Nsp) > South spring soybean (Ssp) > Northeast spring soybean (NEsp), but because of the uneven distribution of SSR variation patterns, the differences between them did not reach a significant level. There was a relationship between genetic distances and geographical distances among soybean populations from different regions, indicating a certain degree of geographical differentiation among Chinese soybean germplasm collections.

In this study, we extended in silico mapping for single trait to analyse data from multiple environments by calculating intraclass correlations and to mapping pleiotropic QTL for multiple traits by defining new statistic to measure the correlation between multiple traits and the marker. Data sets include phenotypes of eight agronomic traits obtained from six different ecologic environments and years, and genotypic information from 477 polymorphic markers on 14 ancestral lines in the pedigree of ÔSuinong14Õ. With in silico mapping, a total of 39 markers distributed on 14 linkage groups are detected as QTL responsible for eight agronomic traits and 10 QTL are identified as having pleiotropic effects. Tracing transmission of functional QTL in the pedigree indicated that certain QTL, such as Sat_036 on linkage group D1a, Satt182 on linkage group L, and Satt726 on linkage group B2 may be responsible for the contribution of exotic germplasm to the improved cultivars.