Fine mapping of qSTV11(KAS), a major QTL for rice stripe disease resistance.

Rice stripe disease, caused by rice stripe virus (RSV), is one of the most serious diseases in temperate rice-growing areas. In the present study, we performed quantitative trait locus (QTL) analysis for RSV resistance using 98 backcross inbred lines derived from the cross between the highly resistant variety, Kasalath, and the highly susceptible variety, Nipponbare. Under artificial inoculation in the greenhouse, two QTLs for RSV resistance, designated qSTV7 and qSTV11(KAS), were detected on chromosomes 7 and 11 respectively, whereas only one QTL was detected in the same location of chromosome 11 under natural inoculation in the field. The stability of qSTV11(KAS) was validated using 39 established chromosome segment substitution lines. Fine mapping of qSTV11(KAS) was carried out using 372 BC(3)F(2:3) recombinants and 399 BC(3)F(3:4) lines selected from 7,018 BC(3)F(2) plants of the cross SL-234/Koshihikari. The qSTV11(KAS) was localized to a 39.2 kb region containing seven annotated genes. The most likely candidate gene, LOC_Os11g30910, is predicted to encode a sulfotransferase domain-containing protein. The predicted protein encoded by the Kasalath allele differs from Nipponbare by a single amino acid substitution and the deletion of two amino acids within the sulfotransferase domain. Marker-resistance association analysis revealed that the markers L104-155 bp and R48-194 bp were highly correlated with RSV resistance in the 148 landrace varieties. These results provide a basis for the cloning of qSTV11(KAS), and the markers may be used for molecular breeding of RSV resistant rice varieties.