Determination of isoflavone (genistein and daidzein) concentration of soybean seed as affected by environment and management inputs

BACKGROUND: Isoflavones, such as genistein and daidzein, are produced in soybean seed [Glycine max (L.) Merr.] and may be associated with health benefits in the human diet. More research is required to determine the effect of agronomic soybean treatments on isoflavone concentration. In this study from 2012 to 2014 at Michigan State University and Breckenridge locations, we have evaluated agronomic input management systems which are marketed to increase or protect potential soybean grain yield, including: nitrogen fertilization, herbicide–defoliant, foliar applied fertilizer, a biological-based foliar application, foliar applied fungicide, foliar applied insecticide, a seed applied fungicide, and a maximized seed treatment that included fungicide and insecticide as well as an inoculant and lipo-chitooligosaccharide nodulation promoter, for their effect on soybean seed genistein and daidzein concentrations. RESULTS: Paired comparisons were made between treatments receiving a designated management input and those without the input. Year and location had a significant effect on isoflavone concentrations. Agronomic management inputs impacted soybean seed daidzein concentrations in 15 of 48 field observations and genistein concentrations in 11 of 48 observations. CONCLUSION: The research supports findings that soybean seed isoflavone levels exhibit a location specific response, and the temporal variability experienced between years appears to influence changes in soybean isoflavone levels more than location.