Analysis of isoflavone contents in vegetable soybeans

In addition to oil and soyfoods, soybean is also produced for vegetable use. The importance of consuming vegetable soybean for the prevention of chronic diseases is well documented. The objectives of this study were to determine the magnitude of genotype x year interactions for isoflavone concentration and pattern, estimate heritabilities, and identify genotypes with a stable isoflavone concentration and pattern. Thirty-one soybean genotypes from maturity groups (MGs) III to VI were grown at Randolph Research Farm of Virginia State University, Petersburg, Virginia, during 3 years. The genotypes were harvested at immature green pod stage (R6-R7) and analyzed for isoflavone contents. Significant (P < 0.05) differences among the genotypes were found for genistein, daidzein, glycitein, and total isoflavones. The genotype x year interactions were also significant (P < 0.05) for the seed traits analyzed, indicating that the performance of the genotype changes from year to year. However, genotypes Pella and Aoda consistently showed with higher means than the overall means for all the seed traits throughout the 3 years. MG differences were also observed for genistein, daidzein, and total isoflavone content. Low- to moderate-heritability estimates of 54, 45, 58, and 64% were observed for genistein, daidzein, glycitein, and total isoflavone content, respectively, suggesting that the seed traits are equally influenced by environments and genetic variations. In general, for all seed traits with the exception of daidzein, the percentage contribution of genotype to the total sum of square was higher than the genotype x year interaction. The seed traits were interdependent and the associations among them were positive and significant suggesting that simultaneous selection and improvements are possible.