2008 Annual Report
The general observation that small increases in temperature during soybean seed development (e.g., 23° vs. 18°C) cause large (around 60%) decreases in isoflavones has been confirmed and extended to multiple soybean lines grown in controlled environments. In all cases, almost all of the decrease occurred with the daidzein and genistein species of isoflavones, which together comprise about 90% of total isoflavones present when developed at 18°C. In contrast, the glycitein family of isoflavones remained approximately constant and consequently become a much larger proportion of total isoflavones at elevated temperature. The basis for this differential regulation is unclear. Elevated atmospheric CO2 at levels expected at the end of this century slightly reduced the effect of elevated temperature, in contrast to earlier studies with a different soybean line showing a much stronger amelioration of elevated temperature effects. The results suggest there may be genetic differences in responses to CO2.
Soybean samples from years representing high and low environmental stress were collected from multiple locations across the state of Maryland and analyzed for isoflavones. Samples were collected from 15 different lines representing soybeans with early to late maturity. Consistent with results from controlled environment studies, content of the daidzein and genistein families of isoflavones was reduced under hot and dry conditions, particularly in the early maturing soybeans, which are more likely to experience environmental stress during seed development. These field studies are consistent with observations from controlled environments.
This project is a multidisciplinary team effort that addresses primarily interactions between atmospheric CO2 and multiple stresses with respect to plant quality in response to the "Cropping Systems" Problem Area of Component III: Agricultural Ecosystem Impacts, of National Program 204 - Global Change and Component 5, "Identifying the health promoting properties of plant and animal foods" of National Program 107 - Human Nutrition.
Britz, S.J., Prasad, P., Moreau, R.A., Allen Jr, L.H., Kremer, D.F., Boote, K.J. 2007. Influence of growth temperature on the amounts of tocopherols, tocotrienols, and y-oryzanol in brown rice. Journal of Agricultural and Food Chemistry. 55:7559-7565.