Genome resequencing reveals genetic loci and genes conferring resistance to SMV-SC8 in soybean.

A soybean natural population genotyped by resequencing and another RIL population genotyped by SoySNP6K were used to explore consistent genetic loci and genes under greenhouse- and field-conditions for SMV-SC8 resistance. Soybean mosaic virus (SMV) is a member of the genus Potyvirus that occurs in all soybean-growing areas of the world and causes serious losses of yield and seed quality. In this study, a natural population composed of 209 accessions resequenced at an average depth of 18.44 × and another RIL population containing 193 lines were used to explore genetic loci and genes conferring resistance to SMV-SC8. There were 3030 SNPs significantly associated with resistance to SC8 on chromosome 13 in the natural population, among which 327 SNPs were located within an ~ 0.14 Mb region (from 28.46 to 28.60 Mb) of the major QTL qRsc8F in the RIL population. Two genes among 21 candidate genes, GmMACPF1 and GmRad60, were identified in the region of consistent linkage and association. Compared to the mock control, the changes in the expression of these two genes after inoculation with SC8 differed between resistant and susceptible accessions. More importantly, GmMACPF1 was shown to confer resistance to SC8 by significantly decreasing virus content in soybean hairy roots overexpressing this gene. A functional marker, FMSC8, was developed based on the allelic variation of GmMACPF1, and a high coincidence rate of 80.19% between the disease index and marker genotype was identified in the 419 soybean accessions. The results provide valuable resources for studies on the molecular mechanism of SMV resistance and genetic improvement in soybean.