Mapping QTL for Individual and Total Isoflavone Content in Soybean Seeds

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Abstract
Dietary intake of isoflavones has been shown to reduce the risk of several major diseases in humans. Therefore, breeding soybean [Glycine max (L.) Merrill] seeds with desirable isoflavone content would be beneficial to the food and health industries, but the environmental sensitivity of the trait complicates phenotypic selection. The objective of this study was to identify quantitative trait loci (QTL) and epistatic interactions associated with isoflavone contents in soybean seeds. A population of 207 F4:6 recombinant inbred lines (RILs) was produced from the cross ‘AC756’ × ‘RCAT Angora’. The population was phenotyped at two locations in Ontario, Canada, and genotyped by means of 99 polymorphic SSR markers. A significant genotype × environment interaction was found. Seventeen QTLs were detected (P < 0.01) by single‐factor ANOVA. Individual loci explained up to 10.5% (P < 0.0001) of the phenotypic variation. Interval mapping and composite interval mapping identified nine genomic regions (LGs A1, C2, D1a, F, G, H, J, K, and M) associated with isoflavone contents. Some QTL associated with agronomic or seed quality traits mapped to the same regions as those for individual isoflavone contents on LGs A1, C2, F, J, K, M, and N. Twenty‐three epistatic interactions were detected for isoflavones. Multiple locus models explained up to 25.0% (P < 0.0001) of the phenotypic variation without epistasis and up to 35.8% (P < 0.0001) with it. The QTL identified in this study could be useful for developing soybean varieties with desirable isoflavone content in the seed through marker‐assisted selection (MAS).