Pyramiding of soybean mosaic virus resistance genes by marker-assisted selection

Soybean mosaic virus (SMV) causes a disease of soybean [Glycine max (L.) Merr.] that is prevalent throughout the United States. The disease can be effectively managed through the deployment of single-dominant resistance genes known as Rsv genes that confer resistance to different strains of SMV. Pyramiding respective Rsv genes from different loci (Rsv1, Rsv3, and Rsv4) through marker-assisted selection (MAS) is an ideal method for creating durable and wide spectrum resistance to all strains of SMV. In this study, simple sequence repeat markers were used to create isogenic lines of the susceptible cultivar Essex containing one, two, or three Rsv loci for observing background and epistatic effects of Rsv1, Rsv3, and Rsv4 on inoculation with six strains of SMV. Results indicate that an Essex background or modifier genes from the donor source had effects on reactions of Rsv3 and Rsv4 genes, causing the isogenic lines to be more susceptible than the Rsv donor parents. Two-gene and three-gene isolines of Rsv1Rsv3, Rsv1Rsv4 and Rsv1Rsv3Rsv4, acted in a complementary manner conferring resistance agains all strains of SMV, whereas isolines of Rsv3Rsv4 displayed a late susceptible reaction to selected SMV strains. We demonstrate with MAS and three near-isogenic lines, each containing a different SMV-resistance genem that pyramided lines can be generated in a straightforward manner into two- or three-gene-containing lines with high levels of resistance to SMV.