Identification and fine mapping of qRBSDV-6 MH , a major QTL for resistance to rice black-streaked dwarf virus disease

Abstract

Rice black streaked-dwarf virus (RBSDV) disease is recently expanding in southern China and poses a serious threat to rice crops. Few studies related to the genetics and breeding of RBSDV resistance have been reported. We have previously mapped a number of quantitative trait loci (QTLs) for RBSDV resistance by using a recombinant inbred line population of ‘Zhenshan 97’ (ZS97, susceptible)/‘Minghui 63’ (MH63, resistant) with natural infection data in two locations. In the present study, we confirmed the presence of a number of resistant QTLs on chromosomes 6, 7, and 9 from MH63 by using the same population in four different locations. We then focused on a major QTL, qRBSDV-6MH, on chromosome 6 and introduced it into a highly susceptible japonica rice variety, ‘Huaidao 5’, using MH63 as the donor via marker-assisted selection, to generate seven backcross inbred lines (BILs). Natural infection and artificial inoculation-based tests revealed that all of the BILs had a significantly higher resistance to RBSDV than the recurrent parent. These results demonstrate that qRBSDV-6MH is a stable major resistance QTL of high breeding value. We also constructed a set of chromosome segment substitution lines (CSSLs) specific to the qRBSDV-6MH region and these used as fine mapping population. Combining the genotypes of CSSLs with the phenotypes from natural infection data in a highly RBSDV epidemic area during two different sowing seasons, we were able to precisely map qRBSDV-6MH to the markers S18 and S23 at a physical distance of 627.6 kb on the Nipponbare reference genome.