A bean common mosaic virus-resistance gene in the soybean variant V94-5152 was mapped to the Rsv4 locus conferring resistance to soybean mosaic virus

Abstract

In the soybean variant V94-5152, a BCMV-resistance gene was mapped near to the region of SMV-resistance Rsv4 locus, raising a possibility that V94-5152 may rely on Rsv4 locus to resist against both SMV and BCMV. Both Soybean mosaic virus (SMV) and Bean common mosaic virus (BCMV) can induce soybean mosaic diseases, but few studies have explored soybean resistance against BCMV so far. In this study, V94-5152, a soybean variant resistant to BCMV and SMV, was crossed with a susceptible cultivar, Williams 82 to map the resistance gene. By inoculating 292 F₂ individuals with a BCMV isolate HZZB011, a segregation ratio of 3 resistant: 1 susceptible was observed, suggesting that V94-5152 possesses a single-dominant resistance gene against BCMV-HZZB011. Bulk segregation analysis (BSA) then revealed that the resistance gene is closely linked to BARCSOYSSR_02_0617, a simple sequence repeat (SSR) marker on chromosome 2. Genotyping neighboring SSR markers among the 292 F₂ individuals enabled us to draw a genetic linkage map, which indicated that the BCMV-resistance gene is located 0.2 cM downstream of BARCSOYSSR_02_0617. Amplification and sequencing ten candidate genes (Glyma02g121300 to Glyma02g122200) around this marker then revealed four genes containing nonsynonymous changes or indels. Also, this location is near to the recently cloned SMV-resistance Rsv4 locus from the cultivar Peking. By obtaining ten more sequences of Rsv4 locus from cultivated and wild soybean materials, we further investigated the variation and evolutionary patterns of this virus-resistance locus. It was evident that positive selections had been acting on this locus, with one critical amino acid change (R55P) shared by all resistance soybeans tested.