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Research Highlights

Research Highlights
Genetic Improvement of Seed Protein: Development of High Protein and High Sucrose Soybean Varieties with Highly Competitive Yields

Figure 1. NIR instrument used to measure protein and oil.

By Amy Miller, Kevin Cook and Bill Rhodes, Benson Hill Seeds

The development of a high-performance soybean variety with high-protein, ultra-low raffinose-stachyose (two indigestible sugars) and high sucrose (digestible sugar) would be a great bonanza for the entire soybean industry. If these soybean varieties could also have desirable agronomics including yield, disease and nematode resistance, they would undoubtedly become the preferred soybean for animal feed and other uses. For over 18 years, this aggressive cross-breeding program has been working to develop such a line of germplasms, and incorporate them into commercial varieties. 

It is well-documented that protein levels in soybeans have been decreasing since the 1980s, so developing lines with high protein content is now a priority. By testing for protein levels in early generations, the number of experimental lines that contain better-than-average protein (40% on a dry weight basis [DB]) has been increased. 

Breeding for protein content is often a challenge because increasing the protein content almost always means lowering the crop yield. Through careful breeding, yields have been maintained at acceptable levels while incremental improvements to protein levels were being made. Each summer in the fields, and in winter nurseries, new combinations of distinctly different parents are crossed to ideally create enhanced offspring. Each new cycle uses a building block approach, combining new protein lines with each other to advance the higher protein materials while simultaneously making other improvements. Once a population reaches the F3 generation, a protein content analysis is run on each individual plant in that population using near-infrared (NIR) analysis. 

Plants that have lower than the desired protein levels are discarded, and not considered as future breeding stock, ensuring that the nursery and testing program is highly efficient. The table below shows one key protein variety, N35D950S, as compared to the currently available commercial checks.

In 2019, this program was funded by USB at the $577,512 level, and provided crucial support for this small company, allowing them to advance and increase varieties with winter productions. In 2019, about 40% of the seedstock production contained these higher protein varieties. Additional new varieties will be products in 2020 and 2021, helping Benson Hill Seeds maintain a leadership in the industry for high protein varieties. 

In the near future, this work will benefit growers by allowing them to produce soybean varieties with a premium demand by both crushers and end users, rather than commodity varieties. More importantly, higher protein levels in U.S.-produced soybeans will help to increase the demand for the U.S. product on the worldwide market, leading to higher prices for U.S. growers. Ultimately, this will allow the U.S. to maintain its reputation of higher-quality soybean quality in a very competitive global market. 

Figure 2. N35D950S head-to-head comparison. Ptn — protein; HGT — height; LDG — lodging; MAT — maturity.

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.