Seasonal changes in temperature and precipitation influence isoflavone concentration in short-season soybean

Future soybean Glycine max (L.) Merr.] cultivars with elevated or reduced concentrations of isoflavones may be required to satisfy the food market. Climate influences isoflavone concentration making their prediction problematic. Our research examined the associations between precipitation and temperature during a growing season with the isoflavone concentration in the harvested seed. We grew 14 cultivars across 12 years, at one location and calculated climate parameters for readily identifiable growth stage intervals (GSI). We correlated the climate parameters within each GSI with seed daidzein, genistein and total isoflavone (TIF) concentrations. We found that cumulative precipitation from the mid-vegetative to the flowering period was correlated with daidzein and TIF concentration. Mean daily average T during early vegetative development was positively correlated with daidzein and TIF concentration and this was largely a result of higher minimum daily T. Accumulated heat stress T greater than 27 °C during seed development was significantly correlated with a reduction in genistein and TIF, but not daidzein concentration. Accumulated cold stress T's less than 20, 15 and 17 °C during seedling emergence were significantly correlated with higher seed daidzein, genistein and TIF concentrations, respectively in all short-season cultivars tested. Cold stress T during seedling emergence could be used to predict seasonal changes in isoflavone concentrations.