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Development of Heat-Tolerant Soybean for the Midsouth

An article titled “As Climate Changes, Southern States Will Suffer More Than Others” was published in the June 29, 2017 edition of the NY Times. The authors, Brad Plumer and Nadja Popovich, composed the article in reference to an article by Solomon Hsiang et al. titled “Estimating Economic Damage from Climate Change in the United States” that appeared in the journal Science (Vol. 356, 1362-1369) in June 2017.

There is no intent here to address the subject of climate change from a political perspective. Rather, the intent is to address the possible scenario of increasing temperatures and how that will affect agriculture in the southeastern US.

The above title of the NY Times article summarizes, in 10 words, what the Science article is about. A brief summary of the specifics cited in these articles as they pertain to agriculture follow.

   As the US confronts potential global warming in the coming decades, not all states will suffer equally; states in the Midwest and Southeast will be especially vulnerable.

   Average agricultural yields in the US are estimated to decline with rising global mean surface temperature (GMST), but higher CO2 concentrations may offset some of this loss.

   Accounting for the estimated effects of CO2 increases, warming still dominates, reducing national yields by about 9% per C increase. Without CO2 increases, temperature and rainfall changes alone would be expected to reduce yields by about 12% per C increase.

   Migration of agricultural production from areas of increasing heat to areas that are less affected could offset some of the loss, or could even result in an increase in agricultural production. However, cropping practices and commodity production would likely be affected/altered.

If the scenario outlined in the above points comes about, crop production in the southern US will have to adapt. That likely will happen through changes in production practices and in the genetics of crop plants that will allow them to produce a profitable and useable yield under higher temperature conditions. With soybeans in the Midsouth, this has already come about to some extent by using the now-conventional ESPS, which is designed to avoid some of the prevalent summer heat in the region.

Dr. Rusty Smith and colleagues at the USDA-ARS research center in Stoneville, Miss. are now addressing the genetic component of soybean adaptation to increasing heat. They determined that the common soybean gene pool lacks heat tolerance, and subsequently identified accessions with heat tolerance within the USDA soybean germplasm collection. They initiated genetic studies and breeding programs to identify specific traits affected by high temperatures, determined the inheritance of tolerance to heat for each trait, and developed improved soybean lines with heat tolerance (manifested as improved seed quality).

The result of the above work has been the development of multiple improved heat-tolerant soybean germplasm lines that are available to both commercial and public soybean breeders and researchers. In a previous study [Metabolomics, Feb. 2016, 12:28], a greater abundance of antioxidant metabolites in a heat-tolerant line indicates that the identified compounds are likely associated with/partially responsible for the greater tolerance of high temperature-tolerant lines to high temperatures during seed development.

One such product is soybean germplasm line DS25-1 (MG IV) with tolerance to high- temperature production environments. This germplasm line was officially released on May 18, 2017, and is the first generation of heat tolerant soybean released in the US.

When this heat-tolerant line was grown for several years at Stoneville, Miss. without irrigation, its average yield was similar to that of check varieties AG 4903 and C4926. Additional genetic studies, as well as stacking this trait with other value-added traits, are in progress. Dr. Smith and colleagues anticipate releasing a second generation of heat-tolerant lines that will have improved yield over the first generation.

Products such as the above will provide developers of new soybean varieties with improved genetic traits that can be incorporated into future varieties to partially offset the negative effects of the hotter production environments that Midsouth soybean producers will likely encounter in coming decades.

Composed by Larry G. Heatherly, July 2017,