Clemson, South Carolina, USA
April 6, 2026
Heat tents help Clemson scientists identify soybean lines that sustain growth and yield under extreme heat
Breeding heat-tolerant soybeans could improve crop resilience during key stages such as flowering and seed filling.
As rising temperatures threaten soybean yields nationwide, scientists from Clemson University and the U.S. Department of Agriculture have identified heat-tolerant soybean lines and key traits that could help develop more resilient crops.
The team evaluated about 200 soybean breeding lines over two growing seasons in South Carolina, exposing plants to temperatures exceeding 100 degrees during critical stages of seed development.
They identified lines that sustained growth and yield under extreme heat, along with traits that could enable breeders to select for heat tolerance more efficiently.
Sruthi Narayanan
“Heat stress during flowering and seed development is one of the most damaging challenges for soybean yield,” said Sruthi Narayanan, an associate professor in the Clemson Department of Plant and Environmental Sciences and the project lead. “In the past, breeders have had very few tools to select for heat tolerance. Our results show that certain traits, particularly aboveground biomass and leaf function, can reliably indicate how well a soybean line will perform under high temperatures.”
In the study, plants maintaining yield under heat stress had higher chlorophyll levels, resulting in healthier, greener leaves. These plants also maintained stronger photosynthetic activity and produced more biomass and seeds.
Total aboveground growth, including stems and leaves, was the most consistent indicator of heat tolerance.
Sachin Rustgi
Sachin Rustgi, an associate professor of molecular breeding at the Clemson Pee Dee Research and Education Center near Florence, South Carolina, and co-author of the study, said identifying both heat-tolerant germplasm and practical selection traits addresses a longstanding challenge in soybean improvement.
“Heat tolerance in plants is hard to pin down because it involves many traits and complex genetics,” Rustgi said. “To make progress, we as scientists need to focus on simple, measurable characteristics and reliable markers that help identify the soybean plants that perform best under stress.”
Malarvizhi Sathasivam
Malarvizhi Sathasivam, a doctoral student in the Department of Plant and Environmental Sciences and a study co-author, said this study will benefit breeders and, ultimately, growers.
“By identifying specific soybean lines that perform well under heat stress and linking yield to traits like biomass and photosynthesis, we are providing breeders with actionable targets they can apply directly in breeding programs,” Sathasivam said.
Benefits for growers
Heat stress is one of several environmental factors affecting soybean production. Shelby Hammond, a Clemson Cooperative Extension Service agronomic agent based in Camden, South Carolina, and study co-author, said breeding heat-tolerant soybeans could improve crop resilience during key stages such as flowering and seed filling.
Shelby Hammond
“But much more than just heat stress goes on in a field,” Hammond said. “Average temperatures during the soybean growing season have been at or above damaging levels, so South Carolina soybeans have already been experiencing heat stress. Some plants that overcome heat stress may also better withstand other environmental factors, such as drought-related stresses.”
Hammond said drought stress often occurs alongside heat stress in South Carolina.
“There is not much a grower can do if heat stress damages a crop other than accept the loss and harvest what they can, unless advised otherwise by their crop insurance company,” Hammond said. “As a Clemson Extension agronomic agent, I see real-time challenges growers face from various stressors.”
What’s next
Narayanan said the results reach far beyond the region.
“Extreme heat events are becoming more frequent across soybean-producing areas,” she said. “The traits and germplasm identified in this study can help accelerate the development of soybean varieties better equipped to maintain yield stability as temperatures continue to rise.”
In the next phase, the scientists will examine how the fats in soybean plants change when the plants get too hot. They’ll compare soybean lines that handle heat well with those that struggle to see how these fat changes might help plants survive high temperatures.
They’ll also search the plants’ DNA for specific genes or markers linked to these helpful traits, as well as other characteristics that make some soybeans more heat-resistant than others.
For more information, read Identification of new germplasm sources and physiological traits for breeding heat-tolerant soybean varieties, in the November/December 2025 issue of Crop Science.
This work is supported by the Agriculture and Food Research Initiative, project award no. 2022-67013-36173, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.
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