Mapping of a major resistance gene to the brown planthopper in the rice [Oryza sativa] cultivar Rathu Heenati

A Sri Lankan indica rice (Oryza sativa L.) cultivar Rathu Heenati was found to be resistant to all the four biotypes of the brown planthopper (BPH) (Nilaparvata lugens Stal). In the present study, we constructed a linkage map to identify the locus (loci) for the BPH resistance genes, using an Fsub(2) population from a cross between Rathu Heenati and a susceptible cultivar 02428. Insect resistance was evaluated using 156 Fsub(2):3 lines and the genotype of each Fsub(2) plant was inferred from the phenotype of the corresponding Fsub(2):3 lines. Three loci detected by QTL (quantitative trait locus) analysis, were assigned to chromosomes 3, 4 and 1 0. The phenotypic variance of the three QTLs indicated that the QTL on chromosome 4 was a major BPH resistance gene in Rathu Heenati. Through linkage analysis, it was found that this BPH resistance gene was located between two SSR markers RM8213 and RM5953 on the short arm of chromosome 4, with map distances of 3.6 cM and 3.2 cM, respectively. This gene, tentatively designated as Bph17, should be useful for the breeding of varieties resistant to BPH in a marker-assisted selection (MAS) program.