Introgression of the Sym2A allele into the European pea cultivar provides the high specificity of legume-rhizobial symbiosis in field conditions

Here, we studied the previously obtained introgression line A33.18 bearing Sym2A in a homozygous state in the genome of European pea cultivar Rondo. A33.18 has proved its high selectiveness in pot experiments. Genome sequencing has shown that A33.18 possesses an 18.2 Mb region inherited from Afghanistan pea with 63 genes, including 5 receptor kinase genes, among which was the most possible Sym2 candidate gene LykX. In a field experiment, under inoculation with nodX+ strain TOM, over 95% nodules of A33.18 contained TOM, as opposed to less than 8% of nodules containing TOM in the parental European cultivar Rondo. Thus, introgression of the Sym2A did enable peers to interact specifically with no dX+ strain, favoring the formation of nodules by the strain from the inoculum and protecting peas from indigenous soil microbiota.