Fine mapping and identification of candidate rice genes associated with qSTV11SG, a major QTL for rice stripe disease resistance

Rice stripe disease, caused by rice stripe virus (RSV) is a serious constraint to rice production in subtropical regions of East Asia. We performed fine mapping of a RSV resistance QTL on chromosome 11, qSTV11 (SG) , using near-isogenic lines (NILs, BC6F4) derived from a cross between the highly resistant variety, Shingwang, and the highly susceptible variety, Ilpum, using 11 insertion and deletion (InDel) markers. qSTV11 (SG) was localized to a 150-kb region between InDel 11 (17.86 Mbp) and InDel 5 (18.01 Mbp). Among the two markers in this region, InDel 7 is diagnostic of RSV resistance in 55 Korean japonica and indica rice varieties. InDel 7 could also distinguish the allele type of Nagdong, Shingwang, Mudgo, and Pe-bi-hun from Zenith harboring the Stv-b (i) allele. As a result, qSTV11 (SG) is likely to be the Stv-b (i) allele. There were 21 genes in the 150-kb region harboring the qSTV11 (SG) locus. Three of these genes, LOC_Os11g31430, LOC_Os11g31450, and LOC_Os11g31470, were exclusively expressed in the susceptible variety. These expression profiles were consistent with the quantitative nature along with incomplete dominance of RSV resistance. Sequencing of these genes showed that there were several amino acid substitutions between susceptible and resistant varieties. Putative functions of these candidate genes for qSTV11 (SG) are discussed.