Evaluation of Diverse Soybean Genotypes for Reproductive Success Under High Temperature Conditions.

Soybean (Glycine max (L.) Merr.) yield is strongly influenced by environmental conditions prevailing during key parts of the growing season. Among the environmental conditions, temperature plays a major role in the success or failure of reproductive structures, and therefore yields. Elevated temperatures not only reduce seed yield through direct negative effects on fertilization, abortion, and seed fill, but also by lowering photosynthesis and increasing respiration. Nearly 240 genetically diverse soybean maturity group (MG) III genotypes were obtained from USDA and their response to heat stress was examined. To this end, plants were grown in pots under field conditions until early flowering, at which time three replications were moved into the greenhouse and one replication was maintained under field conditions. The greenhouse temperature was set to 43/27°C daily maximum/minimum temperature and plants were maintained in this environment until maturity. Several reproductive success and yield traits, including pod number, seed number, and seed per pod were recorded. Additionally, seed weight, seed size, seed wrinkling, germination, and visual rating of the plant. A set of promising extreme (Tolerant and Sensitive) genotypes were identified for physiological studies and to be used as parents for mapping population development.