Two Novel Alleles at the Rsv 3 Locus for Resistance to Soybean Mosaic Virus in PI 399091 and PI 61947 Soybeans

Abstract

ABSTRACTSoybean mosaic virus (SMV) is one of the most destructive viral diseases in soybean [Glycine max (L.) Merr.] worldwide. Soybean mosaic virus isolates collected in the United States have been classified into seven strain groups (G1 through G7). Three loci (Rsv1, Rsv3, and Rsv4) conferring resistance to SMV have been reported so far. Each locus has several alleles that confer different reactions to isolates from the seven SMV strains. Plant Introduction (PI) 399091 and PI 61947 showed a different pattern in response to SMV compared to differential genotypes with known genes, and was therefore assumed to carry novel genes or unique alleles. This study was conducted to determine the inheritance and allelic relationships of SMV resistance genes in these PIs. PI 399091 and PI 61947 were crossed with ‘Essex’ (Rsv), PI 96983 (Rsv1), L29 (Rsv3), and V94‐5152 (Rsv4), and the F2 populations and F2:3 lines from these crosses were inoculated with a G7 isolate. A serological tissue blotting immunoassay (TBIA) was used to confirm the presence of the virus in the infected plants. Selected simple sequence repeat (SSR) markers were used to screen the parents and their progenies to confirm the phenotypic SMV reactions. The results revealed that PI 399091 and PI 61947 each contain an allele at the Rsv3 locus. The phenotypic data were confirmed by SSR markers and TBIA. Based on their unique reaction patterns as compared to other reported Rsv3 alleles, PI 399091 and PI 61947 each contain a novel allele at the Rsv3 locus. We propose that the new symbols of Rsv3‐c and Rsv3‐h be assigned to the resistance alleles in PI 399091 and PI 61947, respectively. These alleles can be considered as valuable sources of resistance to virulent SMV strains.