Researchers have identified an evolutionary trait in soybeans that could help improve yields and strengthen nitrogen fixation, offering a potential pathway to reduce fertilizer use and improve profitability for growers.
The findings, published this month in the Proceedings of the National Academy of Sciences, detail a newly discovered genetic mechanism that regulates soybean nodulation, the process by which soybean roots form nodules that house rhizobia bacteria. Those bacteria convert atmospheric nitrogen into a usable form for the plant, reducing the crop’s dependence on applied nitrogen.
The study was led by Purdue University agronomy professor Jianxin Ma and University of California, Davis plant scientist Blake Meyers.
Soybeans, like other legumes, rely on biological nitrogen fixation to meet much of their nutrient demand. This natural process is central to soybean production because nitrogen is essential for plant growth and protein development.
Researchers said the newly discovered mechanism acts as an internal accelerator for nodulation under low-nitrogen conditions, helping the plant increase nitrogen fixation when nutrient availability is limited. The discovery builds on earlier work by Ma’s team, which in 2019 identified how rhizobia bacteria produce small RNA fragments that help stimulate nodule formation.
In the new study, scientists found soybeans have evolved a complementary plant-based system that helps regulate the process from the host side. The system relies on communication between roots and shoots through small peptides and microRNA molecules.
The researchers found soybeans produce short-chain peptides in the roots that travel through the plant’s xylem into the shoots, where they regulate the production of a specific microRNA. That microRNA then moves back to the roots and suppresses a soybean gene tied to nodulation, creating a feedback loop that helps balance nodule development.
Scientists said the system allows soybeans to avoid the risks of too many or too few nodules. Excess nodulation can drain plant energy, while too little nodulation can leave plants nutrient-deficient in low-nitrogen soils.
The research team identified the mechanism in soybean and found similar pathways in other major legume crops, including common beans, suggesting the findings could have broader applications across pulse and oilseed production.
Using gene-editing technology, Ma’s team modified the pathway to enhance nodulation and nitrogen fixation in the soybean variety Williams 82. In trials, the modified plants showed improved seed quality, increased protein content and higher yields under low-nitrogen conditions.
Williams 82 is a research variety no longer used commercially, but Purdue’s Office of Technology Commercialization has entered testing agreements with potential licensees to evaluate whether the technology can be applied to modern elite soybean varieties.
Researchers said the discovery may complement current grower practices such as seed inoculation with rhizobia or post-planting bacterial applications, potentially giving producers another tool to improve nitrogen efficiency.
The work was supported by the National Science Foundation, National Institutes of Health, United Soybean Board, Purdue AgSEED Program and the Indiana Soybean Alliance.
Source: Purdue University, "Newly discovered soybean biomechanism could increase crop yields"