AUTHOR=Fan Yinglun , Liu Jinge , Lyu Shanhua , Wang Qi , Yang Shengming , Zhu Hongyan 

TITLE=The Soybean Rfg1 Gene Restricts Nodulation by Sinorhizobium fredii USDA193

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01548

DOI=10.3389/fpls.2017.01548

ISSN=1664-462X

ABSTRACT=<p><italic>Sinorhizobium fredii</italic> is a fast-growing rhizobial species that can establish a nitrogen-fixing symbiosis with a wide range of legume species including soybeans (<italic>Glycine max</italic>). In soybeans, this interaction shows a high level of specificity such that particular <italic>S. fredii</italic> strains nodulate only a limited set of plant genotypes. Here we report the identification of a dominant gene in soybeans that restricts nodulation with <italic>S. fredii</italic> USDA193. Genetic mapping in an F2 population revealed co-segregation of the underlying locus with the previously cloned <italic>Rfg1</italic> gene. The <italic>Rfg1</italic> allele encodes a member of the Toll-interleukin receptor/nucleotide-binding site/leucine-rich repeat class of plant resistance proteins that restricts nodulation by <italic>S. fredii</italic> strains USDA257 and USDA205, and an allelic variant of this gene also restricts nodulation by <italic>Bradyrhizobium japonicum</italic> USDA122. By means of complementation tests and CRISPR/Cas9-mediated gene knockouts, we demonstrate that the <italic>Rfg1</italic> allele also is responsible for resistance to nodulation by <italic>S. fredii</italic> USDA193. Therefore, the <italic>Rfg1</italic> allele likely provides broad-spectrum resistance to nodulation by many <italic>S. fredii</italic> and <italic>B. japonicum</italic> strains in soybeans.</p>