Analysis of QTLs for reproductive development and seed quality traits in soybean using recombinant inbred lines

Soybean (Glycine max (L.) Merrill) is the most important leguminous crop in the world due to the high contents of protein and oil, and accumulation of various physiologically active substances. However, most of the genomic and economic traits in soybean are quantitative, controlled by multiple genes and easily affected by environmental conditions. Based on recombinant inbred lines (F-8), a genetic linkage map with 177 RFLP, 150 SSR, 28 AFLP markers and 5 phenotypic markers was constructed. The map covered a distance of 2663.6 cM of the soybean genome comprising 20 linkage groups. The average distance between two adjacent marker loci was 7.89cM. In this population, we detected thirty-nine QTLs for all the reproductive development and seed quality traits investigated, that is, three for flowering time (FT1-3), four for maturity (HAV1-4), three for reproductive period (RP1-3), three for seed hardness (RAS1-3), five for viability of seed (VIS1-5), four for germination rate of seed (GRS1-4), five for water absorbability of seed (WAS1-5) and twelve QTLs for seed weight (SWE1-6 and SWH1-6). Out of these QTLs, twenty-eight were detected in nearly the same regions of the linkage map by both IM (interval mapping) and CIM (composite interval mapping) analysis. The proportion of variance explained of these QTLs ranged from 3.4% to 67.1%. Epistatic interactions were detected among various QTLs. Especially there was a strong interaction among the effects of FTI and FT2, and FT1 and FT3. Multiple correlation coefficients between FT1 and FT2, and FTI and FT3 accounted for 79.6% and 74.1% of the phenotypic variation of flowering time, respectively.