Identification of QTLs for the resistance to rice stripe virus in the indica rice variety Dular

The indica variety Dular has a high level of resistance to rice stripe virus (RSV). We performed quantitative trait locus (QTL) analysis for RSV resistance using 226 F-2 clonal lines at the seedling stage derived from a cross between the susceptible japonica variety Balilla and the resistant indica variety Dular with two evaluation criteria, infection rate (IR) and disease rating index (DRI). The experiments were performed in both 2004 and 2005. Based on IR, three putative QTLs were detected and had consistent locations in the 2 years, one QTL was detected in the RM7324-RM3586 interval on chromosome 3. The other two QTLs were linked and located in the RM287-RM209 and RM209-RM21 intervals on the long arm of chromosome 11, and accounted for 87.8-57.8% of the total phenotypic variation in both years. Based on DRI, three putative QTLs were also detected and had consistent locations in both years. One of them was located in the RM1124-SSR20 interval on the short arm of chromosome 11, while the other two linked QTLs had the same chromosomal locations on chromosome 11 as those detected by IR, and accounted for 55.7-42.9% of total phenotypic variation in both years. In comparison to the mapping results from previous studies, one of the two linked QTLs had a chromosomal location that was similar to Stv-b (i) , an important RSV resistance gene, while the other appeared to be a newly reported one.