Studies conducted in Virginia over a three-year period indicated significant differences (P>0.05) were found for soybean cultivar and genotype x year interactions with isoflavone levels. These results indicate that a cultivar’s isoflavone level varies from year to year. Maturity group differences were seen for genistein, daidzein and total isoflavone content. They reported heritability estimates of 54, 45, 58, 64 percent for genistein, daidzein, glycitein and total isoflavone content, respectively. These data suggest that seed isoflavone levels are influenced by both environment and genetic variables.
Mebrahtu, T. and co-workers. 2004. Analysis of isoflavone contents in vegetable soybeans. Plant Food for Human Nutrition 59(2): 55-61.