The control of earliness has an agronomic importance since it reduces growing and harvesting time. Earliness is controlled by multiple genes in multiple pathways and influenced by the environment. In Arabidopsis thaliana, many earliness related genes were identified. Among them, Arabidopsis Frigida (FRI) gene confers late flowering phenotype, which is reversed to earliness by vernalization. Blast search using FRI against soybean EST database at TIGR identified Isoflavone reductase-like gene (TC217830). Fifty seven SNPs were identified in a total of 4,242 bp lengths in genomic region of Isoflavone reductase-like from 62 soybean genotypes (31 early maturity group and 31 late maturity group). From the obtained sequences, we identified 6 haplotypes of Isoflavone reductase-like gene. Among them, three haplotypes showed a significant association with maturity, suggesting that Isoflavone reductase-like gene is tightly linked to flowering time or actual gene it-self. Thus, to delimit a putative genomic region for maturity and flowering time, SSR markers near Isoflavone reductase-like gene were designed and analyzed for their genetic diversity, assuming that highly selected regions might posses lower genetic diversity. Through these experiments, the region related to maturity and flowering was delimited to nearby ac_satc_4 in scaffold 16.

MADS-box genes encode a family of transcription factors which involve in diverse developmental processes in flowering plants. Because flowering time determines the timing of transition from vegetative to reproductive stage and time to harvest, it would be a significant trait not only to plant it-self but also to breeders. The sequences and gene structures of Arabidopsis MADS-box genes are conserved in model legumes. However, complex genome structure, in soybean, makes it difficult to identify actual genes related to flowering and maturity, although QTL researches have been generally conducted. Therefore, we hypothesized that putative MADS-box genes around the flowering time and maturity QTLs would be candidate genes for those loci. In this study, after surveying 84 QTLs highly associated with maturity and flowering, the QTLs were selected if they were located near 473 putative MADS-box genes. Finally, we found the highly associated 16 SNPs at non-coding region of the putative MADS-box gene around the QTL in 28 late maturity cultivars and 28 early maturity cultivars. Furthermore, by comparing genetic diversity in the cultivated soybeans of late and early maturity groups as well as 20 wild soybeans, selection pattern during domestication was predicted.