Genetic analysis and fine-mapping of Soybean mosaic virus SC7 and SC13 resistance genes in soybean (Glycine max)

Soybean mosaic virus (SMV) is one of the most destructive pathogens of soybean (Glycine max (L.) Merr.) worldwide. In this study, 184 F7:11 recombinant inbred line (RIL) populations derived from Kefeng No. 1 × Nannong 1138-2 were used to study the inheritance and linkage mapping of resistance genes against SMV strains SC7 and SC13 in Kefeng No. 1. Two independent dominant genes (designated Rsc7 and Rsc13) that control resistance to SC7 and SC13 were located on a molecular linkage group (MLG) of chromosome 2 (D1b). A mixed segregating population was developed by self-pollination of three heterozygous plants of residual heterozygous lines (RHL3-27, RHL3-30, RHL3-53) with five markers linked to the loci, and was used in fine-mapping of Rsc7 and Rsc13. In addition, Rsc7 was fine-mapped between BARCSOYSSR_02_0667 and BARCSOYSSR_02_0670 on MLG D1b. The genetic distance between the two closest markers was 0.7 cM and the physical distance of the interval was ~77 kb, which included one LRR gene and another gene containing an F-box region. Two SSR markers (BARCSOYSSR_02_0610 and BARCSOYSSR_02_0621) were closely linked to the SC13 resistance gene. The physical distance where Rsc13 was located was ~191 kb. Sequence analysis showed that there were two K-box region types of transcription factor genes; GmHSP40 and two serine/threonine protein kinase (STK) genes were the most likely candidate genes. These results will facilitate map-based cloning of the Rsc7 and Rsc13 genes and development of transgenic disease-resistant varieties, and will provide SMV-resistance breeding systems with excellent resistance germplasm.