Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2023
Publication Date: 9/4/2023
Citation: Araya, S., Elia, P.E., Quigley, C.V., Song, Q. 2023. Genetic variation and genetic complexity of nodule occupancy in soybean inoculated with USDA110 and USDA123 rhizobium strains. BMC Genomics. 24. Article e520 (2023). https://doi.org/10.1186/s12864-023-09627-4.
DOI: https://doi.org/10.1186/s12864-023-09627-4

Interpretive Summary: Soybean is one of the most important economic crops in the world because it is rich in protein and oil. A unique feature of soybeans and other legumes is root nodulation caused by soil rhizobium bacteria. These bacteria are critical for soybeans to assimilate atmospheric nitrogen into organic compounds, reducing the need for nitrogen fertilizers. There are differences in the nitrogen fixation efficiency among the bacteria strains. In the main soybean producing areas of the Midwest of the United States, the rhizobium USDA123 strain has a high incidence of root nodules in field soybeans, but it is competitive and inefficient in nitrogen fixation. A potential solution to this problem is the identification of soybean germplasm that restricts nodulation to USDA123 but prefers high nitrogen-fixing efficient strains such as USDA110. USDA-ARS scientists evaluated root nodule numbers in over 1400 cultivated and wild soybean accessions inoculated separately and/or simultaneously with USDA110 and USDA123 and identified some soybean accessions that restricted to the rhizobium strain USDA123 but preferred USDA110, they further discovered genomic regions controlling the restriction and preference. In addition, they developed a high-throughput system to characterize nodule number and occupancy. Information from this study will aid in the development of USDA123-restricted cultivars that increase nitrogen fixation efficiency and productivity.

Technical Abstract: Soybean is one of the most important economic crops in the world because it is rich in protein and oil. A unique feature of soybeans and other legumes is root nodulation caused by soil rhizobium bacteria. These bacteria are critical for soybeans to assimilate atmospheric nitrogen into organic compounds, reducing the need for nitrogen fertilizers. There are differences in the nitrogen fixation efficiency among the bacteria strains. In the main soybean producing areas of the Midwest of the United States, the rhizobium USDA123 strain has a high incidence of root nodules in field soybeans, but it is competitive and inefficient in nitrogen fixation. A potential solution to this problem is the identification of soybean germplasm that restricts nodulation to USDA123 but prefers high nitrogen-fixing efficient strains such as USDA110. USDA-ARS scientists evaluated root nodule numbers in over 1400 cultivated and wild soybean accessions inoculated separately and/or simultaneously with USDA110 and USDA123 and identified some soybean accessions that restricted to the rhizobium strain USDA123 but preferred USDA110, they further discovered genomic regions controlling the restriction and preference. In addition, they developed a high-throughput system to characterize nodule number and occupancy. Information from this study will aid in the development of USDA123-restricted cultivars that increase nitrogen fixation efficiency and productivity.