Mapping QTLs for Sheath Blight Resistance in the Rice Line WSS2

The rice line WSS2 which was derived from the Vietnamese indica variety Tetep, displays a high partial resistance to sheath blight. Quantitative trait locus (QTL) analysis of the resistance using simple sequence repeat (SSR) and sequence-tagged site (STS) markers was conducted in a BC1F1 population derived from the cross Hinohikari/WSS2//Hinohikari. Sheath blight resistance in this population and its cross-parents was studied using syringe inoculation. Two QTLs for sheath blight resistance (qSB-3 and qSB-12) were identified on chromosomes 3 and 12. Their resistance alleles were derived from the resistant parent WSS2. These QTLs totally explained 29.6% of the phenotypic variation. Sheath blight resistance was significantly correlated with culm length and heading date. Among the QTLs for culm length and heading date, qCL-3 for culm length was located in the same region as qSB-3, and the remaining QTLs were not linked to qSB-12. Thus, it was reasonable to assume that qSB-12 would enable to breed a rice variety resistant to sheath blight.