Progress has continued in assessing the potential effects of rising temperature on soybean seed yield using our custom-built Temperature Gradient Greenhouse (TGG) system. We completed the assessment of heat stress response for breeding lines developed from crosses between Glycine max x Glycine soja. Two breeding lines (N17-31805 and N19-7165) were found to be resilient to elevated temperatures under conditions where yield losses up to 85% were observed for other breeding lines and the Hutcheson and NC Raleigh Glycine max cultivar parents. This represents significant genetic variation for identification and incorporation of heat tolerance traits for soybean improvement. In 2024 we also initiated screening of a set of Soybean Nested Association Mapping (SoyNAM) parents and the IA3023 “Hub parent” for elevated temperature response using our TGG system. Parental lines that differ from the common IA3023 parent will be used to identify specific SoyNAM mapping populations for further investigation of heat stress markers in soybean.

The genetic variation in response to elevated temperature demonstrated by this project provides a basis for applying traditional breeding approaches to achieve improved heat stress tolerance of soybean. This is important to US soybean growers who will need improved cultivars that perform well under the rising temperatures predicted for the coming decades.