S. Kristipati

Soybean mosaic virus (SMV) is a major viral pathogen, affecting soybean [Glycine max (L.) Merr.] production worldwide. The Rsv3 gene of soybean confers resistance to three of the most virulent strains (G5-G7) of SMV. The objectives of this study were to map Rsv3 and develop polymerase chain reaction (PCR) based markers for marker-assisted selection (MAS) purposes. Disease-response data were collected from two F(2) mapping populations, L29 (Rsv3) x Lee68 (rsv3) and Tousan 140 (Rsv3) x Lee68 (rsv3). Bulk segregant analysis based on amplified fragment length polymorphism (AFLP) markers demonstrated that the Rsv3 locus maps to the soybean molecular linkage group (MLG) B2 between restriction fragment length polymorphism (RFLP) markers A519 and Mng247. These two tightly linked RFLP markers were converted to PCR-based markers to expedite MAS. Sequence analysis of the Mng247 genomic region revealed similarity to the consensus sequence of a leucine-rich repeat (LRR) characteristic of the extracellular LRR class of disease resistance genes. Results from this study will be useful in pyramiding viral resistance genes and in cloning the Rsv3 gene.

Soybean mosaic virus (SMV) is a major viral pathogen, affecting soybean [Glycine max (L.) Merr.] production worldwide. The Rsv3 gene of soybean confers resistance to three of the most virulent strains (G5–G7) of SMV. The objectives of this study were to map Rsv3 and develop polymerase chain reaction (PCR) based markers for marker-assisted selection (MAS) purposes. Disease-response data were collected from two F2 mapping populations, L29 (Rsv3) × Lee68 (rsv3) and Tousan 140 (Rsv3) × Lee68 (rsv3). Bulk segregant analysis based on amplified fragment length polymorphism (AFLP) markers demonstrated that the Rsv3 locus maps to the soybean molecular linkage group (MLG) B2 between restriction fragment length polymorphism (RFLP) markers A519 and Mng247. These two tightly linked RFLP markers were converted to PCR-based markers to expedite MAS. Sequence analysis of the Mng247 genomic region revealed similarity to the consensus sequence of a leucine-rich repeat (LRR) characteristic of the extracellular LRR class of disease resistance genes. Results from this study will be useful in pyramiding viral resistance genes and in cloning the Rsv3 gene.

Soybean mosaic virus (SMV) is the major virus disease reported all over the world in soybean crop. This disease causes reduction in the yield and quality of soybean crop. Three independent genes Rsv1, Rsv3, and Rsv4, were found to provide host resistance in soybean. Rsv1 confers resistance to all but most virulant strains of SMV. Rsv1 has been mapped to soybean molecular linkage group (MLG) F by using molecular markers. \nThe purpose of this study is to investigate the location of Rsv3 gene on soybean map using molecular markers. The Rsv3 gene of soybean confers resistance to the most vurulent strains (G5-G7) of SMV. In order to map the gene, an F2 population was constructed from a cross between L29, an Rsv3 isoline of 'Williams', and 'Lee 68', a susceptible cultivar. Rsv3 genotypes of 183 F2 plants were determined by inoculating F2:3 progeny with the G7 strain of SMV. \nA preliminary survey of two parental lines, near isogenic lines (NILs), and bulk segregants with 136 restriction fragment length polymorphism (RFLP) markers yielded 36 markers showing variation between the two parents. These polymorphic RFLP markers unable to provided any indication of linkage to Rsv3. \nAs an alternative strategy, amplified fragment length polymorphic (AFLP) marker analysis of the two parental lines, NILs and bulk segregants was performed using 64 primer combinations. Initial breakthrough came in the form of AFLP primer combination of Eco+AAC/Mse+CTG exhibited polymorphism between NILs, bulk segregants, and two parental lines. This AFLP marker was isolated and cloned to convert it into a RFLP clone to further investigate the linkage to Rsv3 by F2 segregation analysis. \nA mapping population constructed by crossing Glycine max x Glycine soja employed in determining the location AFLP-derived RFLP clone on soybean linkage map. This population has densely mapped molecular marker data that enabled determining the location of AFLP-derived RFLP clone ACR1 on soybean molecular linkage group (MLG) B2 between the markers pA516 and pA519. \nThis finding, made it easy to establish the linkage of markers pA519, pA516, and pA593 in L29 x Lee 68 population by F2 segregation analysis. The closest marker linked pA519, was 0.9 cM away from Rsv3. In another study Rsv4 is reported to be mapped to MLG D1b of soybean. \nResults of this study are useful in marker-based selection (MAS), pyramiding viral resistance genes and in cloning the Rsv3 gene.