Linkage Mapping and QTL Analysis of Isoflavones Composition in Soybean Seeds

The high isoflavones content of soybeans is an important breeding goal due to the demonstrated benefits of isoflavones to human health and their association with plant resistance. In this study, quantitative trait loci (QTL) mapping for soybean isoflavone aglycones, including daidzin, glycerin, and genistin, and total isoflavones content was performed in a population of 178 F2:6 recombinant inbred lines (RILs) which was generated from a cross between varieties Jinong 17 and Jinong 18. A genetic linkage map covering 1248 cM was constructed using the simple sequence repeat (SSR) molecular markers. The results revealed 22 isoflavone-related QTLs, 5 for daidzin, 7 for genistin, 6 for glycerin, and 4 for total isoflavone content. Seven of these represented new QTLs. All QTL regions contained 6462 genes, of which 58 have been annotated for flavonoid synthesis. Using public databases, three candidate genes, namely Glyma.11G164400, Glyma.16G158400, and Glyma.19G217700, were subsequently identified. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) demonstrated that the three genes exhibited specific, high expression in soybean seeds and a positive correlation with flavonoid content. These findings might be helpful in the efforts to breed new soybean varieties with improved isoflavone composition and content.