Sinorhizobium fredii is a rhizobial species that can establish a
nitrogen-fixing symbiosis with a wide range of legume species. In soybean
(Glycine max), this interaction shows a high level of specificity since S.
fredii strains nodulate only on a limited set of soybean genotypes. The team
of Yinglun Fan from the Liaocheng University in China identified a gene in
soybean that restricts nodulation with S. fredii USDA193.
Using complementation tests as well as the Crispr-Cas9 knock-out, the team
found that the Rfg1 allele was responsible for resistance to nodulation by
S. fredii USDA193. in previous studies, the Rfg1 allele was found to encode
a class of plant resistance protein that restricts nodulation by S. fredii
strains USDA257 and USDA205. Another version of this gene also restricts
nodulation by Bradyrhizobium japonicum strain USDA122.
The Rfg1 allele likely provides broad-spectrum resistance to nodulation in