Fine mapping of GRH3 conferring resistance to green rice leafhopper in rice (Oryza sativa L.)

Green rice leafhopper (GRH) is a major sap-sucking insect pest that causes large annual yield losses in rice by transmitting the rice dwarf virus or spreading sooty mold fungi. Genetic resistance is the most effective approach to control GRH as well as the spread of diseases. We performed a genetic analysis to detect the GRH resistant region in rice cv. ‘Cheongnam’ using bulk segregant analysis of the F2 population derived from a cross between GRH-resistant cv. ‘Cheongnam’ and GRH-susceptible cv. ‘Junam’. Two simple sequence repeat (SSR) markers, RM6818 and RM20142, demonstrated polymorphism between the parents, and between the resistant and susceptible bulks, and were located at the same region of GRH3 on chromosome 6. GRH3 was narrowed down to an interval between the RM20132 and RM20152 SSR markers, covering a 435-kb region of the ‘Nipponbare’ genome. We tested 1,000 individuals of the F2 population and 20 germplasm accessions and determined that GRH resistance co-segregated with SSR markers RM20142 and RM20145, which reside within the 435-kb region. This result demonstrates that these closely linked SSR markers are a convenient tool for the selection of GRH-resistant lines and cultivars.