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Research Highlights

Research Highlights
Utilizing Genes from the Soybean Germplasm Collection to Mitigate Drought Stress

Figure 1. Rain out shelter to experimentally mimic drought conditions.

By Larry C. Purcell, University of Arkansas

A primary factor affecting the stability of soybean yield from year to year is water. Every year, drought impacts soybean yield in some part of the U.S. Each year from 1986-2016, drought has impacted between 3-59% of the U.S. soybean production area. For 10 of those years, drought affected 20% or more of the soybean production areas. The vulnerability of soybean to drought introduces volatility into the market, and predicted climatic conditions will likely only exacerbate these issues. This project is focused on identifying specific soybean genotypes that provide drought tolerance, and transferring the beneficial genes to high-yielding, elite lines to help provide resilience in the soybean crop of the future. In 2019, the project was funded at the $425,953 level. 

Figure 2. Proportion of US soybean production area impacted by drought from 1986 to 2016. Stippled bars indicate years in which drought impacted >20% of the production area. 

The USDA Soybean Germplasm Collection has over 22,000 different soybean genotypes, with everything from ancestral genotypes grown by farmers in East Asia thousands of years ago to more recent, high-yielding genotypes from the U.S. Included in the collection are soybeans from areas with harsh, dry climates that have favorable traits for drought environments. 

This research has capitalized on prior USB-sponsored research that provided molecular marker data on all 22,000 accessions. This data allowed for rapid identification of specific DNA regions that contribute to drought tolerance. 

Three hundred seventy-three diverse maturity group 4 (MG 4) accessions were evaluated in irrigated and rainfed experiments at sites in Arkansas, Missouri, Mississippi and Arizona. MG 4 accessions are a common link between germplasm in the southern and northern U.S. Favorable DNA regions (alleles) associated with four drought-related traits — high water use efficiency, slow canopy wilting, cool canopy temperature and high nitrogen fixation — were identified. 

Figure 3. Root architecture can impact the plant’s ability to utilize soil moisture at different depths.

The favorable alleles for these traits are being transferred from the unadapted accessions into high-yielding, adapted, elite lines using conventional and marker-assisted breeding methods. In 2019, accessions with a large number of favorable alleles for each trait were crossed with an elite line, and the hybrid seed was used to begin inter-trait crosses, including crossing water use efficiency with high nitrogen fixation and crossing slow canopy wilting with cool canopy temperature. In 2020, crosses with the hybrid seed will be made to combine all four traits into the same genetic background. Subsequent research will utilize molecular markers to determine the progeny possessing the most favorable alleles, and those lines will be evaluated for drought tolerance and yield under rainfed conditions.

Often the impacts of drought go undetected, because yield is impacted before there are any visible signs of wilting or stress. This research will provide elite, high-yielding germplasm with a combination of the four traits that confer drought tolerance that will be available for crossing with other cultivars. The drought-resilient soybean cultivars developed will provide an economical means of lessening the impact of drought and ultimately benefit both producers and consumers wherever soybean is grown.

This project was funded by the soybean checkoff. To find research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.