The Rsv3 Locus Conferring Resistance to Soybean Mosaic Virus is Associated with a Cluster of Coiled-Coil Nucleotide-Binding Leucine-Rich Repeat Genes

The Soybean mosaic virus (SMV) resistance locus, Rsv3, previously mapped between markers A519F/R and M3Satt in the soybean molecular linkage group B2 (chromosome 14), has been characterized by examination of the soybean genome sequence. The 154 kbp interval encompassing Rsv3 contains a family of closely related coiled-coil nucleotide-binding leucine-rich repeat (CC-NB-LRR) genes. Tightly linked to this region are additional CC-NB-LRR genes and several leucine-rich repeat receptor-like kinase (LRR-RLK) genes, thereby indicating that members of both multigene families constitute a heterogeneous cluster at the Rsv3 chromosomal region. To further confirm the sequence and genetic map concordance, we developed 16 markers from the genomic sequence including predicted CC-NB-LRR genes and their flanking sequences. Mapping of the resultant markers in three populations showed parallel alignment between the genetic and sequence maps in the Rsv3-containing region. Phylogenetic analysis of five CC-NB-LRR genes including a pseudogene showed they were highly similar to each other and formed a subclade within a CC-NB-LRR gene clade with representatives from several plant families including legume species. These results demonstrate that the Rsv3 locus is associated with this cluster of CC-NB-LRR genes, thereby suggesting that the Rsv3 gene most likely encodes a member of this gene family. In addition, information from this study should facilitate marker-assisted selection and pyramiding of resistance genes.