Genetic studies and identification of QTLs for sheath rot disease resistance in rice (Oryza sativa L.)

Rice genotypes BPT5204 and HP14, their direct and reciprocal F(1)s (DF1&RF1), F-2 populations (DF2&RF2) and recombinant inbred lines (RILs) were evaluated to study the genetics of field resistance to sheath rot disease (ShR). Observed frequencies of resistant and susceptible plants in DF2 and RILs showed 27R:37S ratio and 1R:7S ratio indicating involvement of three dominant genes with complementary gene action. Significant differences between two crosses were observed between DF1&RF1, and DF2&RF2 for panicle exertion and sheath rot attributing traits indicating the role of cytoplasm in manifestation of sheath rot resistance. Plants with anthocyanin pigmentation recorded significantly higher mean for panicle exertion and higher level of resistance to sheath rot disease in both F(2)s and RILs. Single marker analysis indicated association of anthocyanin with sheath rot resistance making purple pigmentation as probable morpholigical marker for it. Composite interval marker analysis revealed qShR-12 located on chromosome-12 and flanked by SSR markers RM7315 and RM28118 accounting 11.78% of cumulative phenotypic variation. This is the first report on genetics, role of cytoplasm, association of anthocyanin pigmentation and SSR markers with sheath rot disease resistance.