Soybean yield improvement typically increases seed oil content at the expense of protein content in the meal. Today, one of the largest factors for determining the value of U.S. soybean is protein content, dictating the high demand from the soybean industry for high-protein soybean seeds. Developing germplasm with seed compositions tailored to the needs of the industry will improve the value of soybean and help it to stay competitive with other feedstocks. To address the industry needs, the southeastern soybean breeding program developed soybean lines with high protein contents (~49%-53%). The proposed project will test those lines for oil composition under optimal, drought, and heat stress conditions. Our goal is to identify the high-protein (>45%) soybean genotypes that also maintain desirable oil content (~17-18%) and composition (e.g., high oleic acid and low linolenic acid contents) under optimal, drought, and heat stress conditions. These lines will then be used to develop new varieties with high yield and desirable protein and oil quantity and quality not only under optimal conditions but under drought and heat stresses.

Test how the high-protein trait combines with other value-adding traits such as high oleic acid and low linolenic acid contents under optimal conditions and drought and heat stresses.

This project will identify high-protein (>45%) soybean genotypes that also maintain desirable oil content (~17-18%) and composition (e.g., high oleic acid and low linolenic acid contents) under drought and heat stresses, by the end of the project period. These lines will then be used to develop new varieties with high yield and desirable protein and oil quantity and quality not only under optimal conditions but under drought and heat stresses.

We will deliver the results from the proposed project to farmers through field days, grower meetings, publication of extension articles on relevant websites targeting soybean producers, scientific manuscript, personal communications, presentation at the South Carolina Soybean Board meeting, and quarterly and final reports to the Board. We also plan to work with Denise Attaway, Clemson PSA Media Relations, to relay information about this project to the public. This will involve local, state, and regional media with print stories.

Key Performance Indicators:

New information generated on an industry-valued trait (high protein) of soybean: We will generate information on the impact that increased protein can have on other value-adding traits such as oil content and composition (oleic and linoleic acid contents) and amino acid composition and yield. These results should be available in a single year at the end of the project term.

Germplasm lines and new varieties: The ultimate long-term deliverable for this project will be the release of increased protein (>45%) germplasm and varieties that can be utilized by the soybean industry to improve the seed composition and the value of US soy. The breeding lines will be made available for use by breeders in the public and private sectors to develop future varieties.

Soybean genetic improvement has historically focused on increasing yield, which typically increases seed oil content at the expense of protein content in the meal. Although yield remains the top priority, improvements to seed composition have become very important and can have a significant impact on value. Protein and oil content account for around 60% of the total dry weight of soybean seeds, of which around 20% is oil and 40% is protein. A bushel of soybeans produces around 11 pounds of oil and at $0.7 per pound, it is worth $7.7. At the same time, a bushel of soybean produces around 48 pounds of soybean meal and at $500 per ton, it is worth $12 a pound. This indicates the importance of high-protein soybeans to enhance the profitability of soybean production.

Soybean meal accounts for two-thirds of the protein meal used in poultry and livestock production. Close to 75% of the total soybean meal produced in the US is used by the poultry and swine production industries. Currently, fish meal contains higher crude protein than solvent-extracted soybean meal. By 2030, the demand for aquaculture production is expected to grow between 35-40 % (FAO, 2022). With the depletion of fish stocks, fish meal may become more expensive or less abundant. In that case, what will be the source of nutrition for the growing poultry and swine markets? Soybeans? Thus, developing a high-protein soybean could not only address the current demands of the soybean industry but potential future markets as well.

As per the US Soybean Export Council, three major factors that set US soy apart and determine its value in the global market are higher protein content, better amino acid profile, and enhanced amino acid digestibility. Studies show a strong negative correlation between oil content and the levels of arginine, leucine, and methionine- three essential amino acids in soybean seeds. Other amino acids that show a decrease with increasing oil concentrations are isoleucine, lysine, valine, cysteine, threonine, and tryptophan (Assefa et al., 2018). These data suggest that allowing a lower oil content may permit improvements to be made in the amino acid composition of seed protein, which could have a large impact on determining the value of US soy. To date, most research has focused on increasing the protein content in soybean while maintaining at least 20% oil content. By increasing the protein content beyond what is normal while decreasing the oil content by only 2-3% may offer the possibility of a greater improvement in the amino acid composition.

In the above-explained context, the southeastern soybean breeding program (led by Dr. Ben Fallen) developed soybean lines with high protein content (~49-53%) and an oil content of ~17-18%, with the support of the United Soybean Board. Dr. Fallen’s group is evaluating these lines for yield and meal composition (amino acid profiles) and ensuring that there is no decline in protein functionality as protein levels increase. To meet market demands and maximize profitability, it is imperative to test how stable the high protein trait is under environmental stress conditions and how the trait combines with other value-adding traits such as high oleic acid and low linolenic acid contents under stress conditions. Last year, Dr. Sruthi Narayanan’s group tested Dr. Fallen’s genotypes under drought and heat stresses and found that the high-protein trait is stable under drought and heat stresses. As the next step, we want to test any impact of the high-protein trait on oil composition, which is the goal of the proposed project.