Evaluation of Response of Modern Soybean Cultivars in Arkansas to Soybean Mosaic Virus (SMV).

Soybean mosaic virus (SMV) is one of the important soybean viral diseases which causes drastic reduction of seed yield and quality. Seven SMV strains, G1 to G7, have been identified and three dominant genes, Rsv1, Rsv3, and Rsv4, have been reported. The objective of this study was to screen modern soybean cultivars for resistance to SMV. A total of 303 cultivars currently grown in Arkansas were screened in the greenhouse. Each genotype was planted in three separate pots; two for inoculation with each of six SMV strains (G1, G2, G3, G5, G6, and G7), and one for control. The inoculation was done using a mortar and pestle. The soybean genotypes were classified as resistant (R, symptomless), necrotic (N, stem-tip necrosis), or susceptible (S, mosaic). The virus was detected serologically with enzyme-linked immunosobent assay (ELISA), and tissue blotting assay (TBA). The results demonstrated that 197 cultivars were susceptible to all SMV strains. Fifty seven cultivars were R to G1 but R, N, or S to some of higher numbered strains; therefore, they may carry one of the resistance alleles at Rsv1 locus. Two cultivars were S to G1 through G3 and R through G5 to G7; therefore, they may carry an Rsv3 allele. Two cultivars were R to all SMV strains and may carry Rsv1-h, Rsv4 or two genes of Rsv1Rsv3, Rsv1Rsv4, or Rsv3Rsv4. Thirty nine cultivars showed R to G1, but exhibited a different reaction pattern to higher-numbered strains; they may carry new alleles of Rsv1. Eleven cultivars were S to G1, but R to higher-numbered strains; they may carry new alleles of Rsv3. Research is ongoing to confirm theses new SMV resistance alleles through genetic and molecular study.