Isoflavones in Korean soybeans differing in seed coat and cotyledon color

The seeds of 268 soybean [Glycine max (L.) Merrill] varieties cultivated at five sites in Korea were categorized into five groups according to their seed coat color (i.e. black, brown, green, mottled and yellow). Seeds were analyzed for their isoflavone concentrations, and the relationship between seed color and isoflavones was investigated. Soybean varieties were also divided according to their cotyledon color (i.e. yellow and green) to investigate possible relation with isoflavones. Overall, differences between soybeans differing in seed coat or cotyledon color were minimal and largely inconsistent across sites. A few differences were observed for the isoflavones that were present in the largest concentrations (i.e. daidzin, genistin, malonyldaidzin and malonylgenistin). However, brown soybeans consistently had greater proportions of aglycones due to a 300% greater concentration of glycitein compared to soybeans of other colors. Results suggest that isoflavone concentration differences between soybeans differing in seed coat and cotyledon color are mainly indicative of environmental and genotype-by-environment effects. Selection and breeding for isoflavones can be done irrespective of seed coat and cotyledon color.