Effect of Temperature at Reproductive Growth Stages on Soybean Seed Yield and Quality Traits.

Soybean [Glycine max (L.) Merr.] is produced across a wide range of temperature and management practices. Temperatures during seed growth and development will not only affects seed yield, but also impacts seed quality. The objectives this study was to investigate temperature effects on soybean yield and quality under optimum water and nutrient conditions. Two soybean cultivars, Asgrow AG5332 and Progeny P5333RY, from Maturity Group V grown outdoors in sunlit in pots were moved into the sunlit plant growth chambers prior to flowering. Five day/ night temperatures, 21/13, 25/17, 29/21, 33/25, and 37/29 °C, were imposed at initial flowering stage. Total biomass, seed yield, and quality were assessed at maturity. Seed yield differed significantly between the cultivars and among the temperatures. Quadratic functions best described the temperature and seed yield response functions in both the cultivars, optimum temperature was 26°C for Asgrow AG5332 and 23°C for Progeny P5333RY; seed decline was much steeper in Progeny P5333RY than Asgrow AG5332. Temperature affected all seed quality parameters in both cultivars. Even though, protein content was unaffected by temperature and cultivars, seed oil increased up to 25°C and declined at higher temperatures. Pamitic and stearic acids showed a quadratic response to temperature while linoleic and linolenic acids declined linearly with temperature. Oleic acid, on the other hand, was not different at three lower temperatures, but increased at higher temperatures. Sucrose, raffinose and stchyose contents declined with increase in temperature in both the cultivars. The functional relationships between temperature and soybean seed quality parameters will be useful to develop seed quality-specific sub-models. Soybean models with integrated seed quality modules would be useful not only for production optimization of natural resources such as water and nutrients, but also useful in assisting for planting and policy decisions in both the current and projected warmer future environments.