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A new article published by Virginia Tech researchers and graduate students has revealed that soybean root nodules harbor high abundances of atypical non-nitrogen fixing bacteria, a discovery that has the potential to improve the crop resilience and yield of the crop.

Pertinent to the growth of soybean is a type of bacteria, diazotrophs, that live in the plant's root nodules. These bacteria provide soybean with nitrogen required for growth. This nitrogen is the main constituent of protein.

Soybean, which is grown for its protein and oil contents, was the most planted crop by area in the United States in 2018, overtaking corn as the country’s leading cash crop. It is currently the main source of protein for livestock, poultry, and swine. The soybean industry is worth about $40 billion a year.

Hazem Sharaf, a graduate research assistant in the lab of Mark Williams, was the first author on the paper. Williams is an associate professor in the School of Plant and Environmental Sciences in the College of Agriculture and Life Sciences.

The study, which was published in the high-impact journal Microbiome, has revealed that root nodules of soybean plants include non-diazotroph bacteria like Pseudomonas and Enterobacteria. In some of the soybean plants, they occupied as much as 40 percent of the nodule bacterial population. These bacteria did not have the iron nitrogenase gene, nifH, so they were determined not to be fixing nitrogen. Subjecting their soybean hosts that were planted at Virginia Tech’s Kentland Farm to different irrigation treatments did not significantly alter the abundances of these non-diazotrophs inside the sensitive nodules.

“This is akin to recent discoveries related to human medicine, where the human gut microbiome can have positive impacts on improving our health. Improving soybean nodule microbiome will definitely reflect positively on plant health and yield,” said Sharaf.

Although the role that these bacteria play is still not known, their presence in high abundance did not affect the yield negatively. Amino acids that are involved the nitrogen exchange between the bacteria and the plant were not impacted by them as well. The research team speculates that their presence serves a plant-growth promoting role from within the nodule.

“Our research findings open the door for other research and the industry to expand on these results and explore new ways of improving their soybean using these bacteria,” Sharaf said.

These results will benefit soybean growers and breeders throughout the country and the world. They would change the way the manage their soybean crops, for example, by inoculating these newly identified bacteria to their plants, thus improving their resilience, and potentially reducing their yield losses. Soybean breeders can also develop new varieties of soybean that would be able to recruit these beneficial bacteria as well.

Source: https://vtnews.vt.edu/