did not infect any of the resistant cultivars. However, the most virulent strain, G7, infected all cultivars tested Soybean mosaic virus (SMV) causes one of the most destructive and caused necrosis in Marshall, Ogden, Kwanggyo, and viral diseases in soybean [Glycine max (L.) Merr.] worldwide. Ninetyeight SMV isolates identified in the USA have been classified into Buffalo and mosaic symptoms in Davis and York. seven strain groups (G1-G7). Three independent loci (Rsv1, Rsv3, Various sources of SMV resistance have been identiand Rsv4) have been identified for SMV resistance. Multiple resisfied in soybean. Several gene symbols have been astance alleles have been reported for the Rsv1 and Rsv3 locus. The signed for the SMV-resistance alleles identified in the objective of this research was to group diverse soybean genotypes on USA. There are three independent loci reported so far the basis of their differential reactions to SMV strains. SMV strains for SMV resistance, Rsv1, Rsv3, and Rsv4. Eight resis-G1 and G7 were used to characterize the reactions of 212 soybean tance alleles have been identified at the Rsv1 locus, genotypes to SMV. Fifty-five genotypes were resistant to G1 but namely, Rsv1 in PI 96983, Rsv1-t in Ogden, Rsv1-y in susceptible to G7, and virus was detected in G7-inoculated plants. York, Rsv1-m in Marshall, Rsv1-k in Kwanggyo, Rsv1-r Thirty-one genotypes were resistant to G1 but exhibited stem-tip in 'Raiden', Rsv1-h in 'Suweon 97', Rsv1-s in LR1, and necrosis following G7 inoculation. These 86 soybean genotypes presumably carry alleles at the Rsv1 locus. Thirty-seven genotypes were Rsv1-n in PI 507389 (Buss et al., 1997; Buzzell and Tu, resistant to G1 and G7, and SMV was not detected by ELISA, indicat-1989; Chen et al.; Kiihl ing that they probably carry Rsv4, Rsv1-r, or Rsv1-h or a combination and Hartwig, 1979;Ma et al., 1995 Ma et al., , 2003. Two alleles of two resistance genes Rsv1Rsv3, Rsv1Rsv4, or Rsv3Rsv4. Seven for SMV resistance have been reported at the Rsv3 genotypes were susceptible to G1 but resistant to G7 and may carry locus; one was identified in OX 686 soybean line derived alleles at the Rsv3 locus. PI 507389 and PI 61944 developed stemfrom the cultivar Columbia (Buzzell and Tu, 1989), and tip necrosis after inoculation with G1 and a mosaic symptom when the other was found in L29 soybean derived from the inoculated with G7, indicating that PI 61944 may carry the same cultivar Hardee (Buss et al., 1999). The Rsv4 locus was Rsv1-n gene as PI 507389. Eighty soybean accessions developed moidentified in a breeding line V94-5152 derived from PI saic symptoms when inoculated with G1 or G7 because of the lack 486355 ϫ 'Essex' and was shown to confer resistance

Soybean mosaic virus (SMV) is one of the most destructive viral diseases in soybean (Glycine max). Three independent loci for SMV resistance have been identified in soybean germplasm. The use of genetic resistance is the most effective method of controlling this disease. Marker assisted selection (MAS) has become very important and useful in the effort of selecting genes for SMV resistance. Single nucleotide polymorphism (SNP), because of its abundance and high-throughput potential, is a powerful tool in genome mapping, association studies, diversity analysis, and tagging of important genes in plant genomics. In this study, a 10 SNPs plus one insert/deletion (InDel) multiplex assay was developed for SMV resistance: two SNPs were developed from the candidate gene 3gG2 at Rsv1 locus, two SNPs selected from the clone N11PF linked to Rsv1, one 'BARC' SNP screened from soybean chromosome 13 [linkage group (LG) F] near Rsv1, two 'BARC' SNPs from probe A519 linked to Rsv3, one 'BARC' SNP from chromosome 14 (LG B2) near Rsv3, and two 'BARC' SNPs from chromosome 2 (LG D1b) near Rsv4, plus one InDel marker from expressed sequence tag (EST) AW307114 linked to Rsv4. This 11 SNP/InDel multiplex assay showed polymorphism among 47 diverse soybean germplasm, indicating this assay can be used to investigate the mode of inheritance in a SMV resistant soybean line carrying Rsv1, Rsv3, and/or Rsv4 through a segregating population with phenotypic data, and to select a specific gene or pyramid two or three genes for SMV resistance through MAS in soybean breeding program. The presence of two SMV resistance genes (Rsv1 and Rsv3) in J05 soybean was confirmed by the SNP assay.