Development of SNP Markers and Analysis of Rsv4 Candidate Gene of Soybean Mosaic Virus Resistance.

Soybean mosaic virus (SMV) is one of the most prevalent pathogens in soybean transmitted by aphids and infected seeds. Chemical and cultural control of SMV is neither economical nor environment-friendly. Deployment of genetic resistance is considered to be the most effective and feasible alternative to control the disease. Seven SMV strains, G1 through G7, and three independent loci for SMV resistance, Rsv1, Rsv3, and Rsv4, with multiple alleles have been identified. The objective of this research was to develop SNP markers and propose Rsv4 candidate gene. The chromosomal region containing a candidate gene of 10 cultivars was sequenced using gene specific primers. Three SNPs were identified close to the Rsv4 locus. In addition, over two hundred soybean germplasm lines, collected worldwide were subjected for genotyping using the Sequenom iPLEX Gold platform. In total, 20 SNP primers were designed to genotype Rsv4 region. Moreover, the lines were inoculated with G1 and G7 SMV strains in a greenhouse to establish their foliar symptoms. Furthermore, the cross between V94-5152 (Rsv4) and Lee 68 (rsv) was made, and 766 plants from F2 population were used to validate three discovered SNPs closely linked to the Rsv4 locus. For fine mapping, several SNPs on the two sides of the target SNP makers were added with r>0 to validate the target SNPs. The Rsv4 gene location has been proposed. The information from this research can be helpful in selecting crossing parents for SMV breeding what could accelerate breeding efforts to develop multi-virus resistant crops.