Validation and Fine-Mapping of Genetic Locus Associated with Resistance to Brown Plant Hopper [Nilaparvata lugens (Stal.)] in Rice (Oryza sativa L.)

In the present study, an attempt was made to validate and fine-map the genetic locus associated with brown planthopper (BPH) resistance locus from IR71033-62-24, a derivative of O.sativa/O.minuta cross, using simple sequence repeats (SSR markers). A F₆ segregating population 300 individuals were developed by crossing IR71033-62-24 with a highly susceptible variety, Mahsuri scoring 4.5 and 9.0 (on the scale 1-9) to BPH in greenhouse screening experiments. A subset of 84 F₆ individuals was phenotyped for BPH resistance using a standard seedbox screening test (SSST) under greenhouse conditions. The mean phenotypic score of the subset population was 6.7 and the population was skewed towards the susceptible parent by -0.32. A subset of 61 individuals with extreme phenotypic score was selected from the population for marker trait association analysis. Through single marker analysis,it was found that the BPH resistant locus Bph 22(t) was located at a distance of 6.7cM from the SSR markers RM 585,RM 225,RM 584, RM 19429 and 12.7cM from RM 204 on the long arm of chromosome 6 with a probability value of 0.00.A subset of 75 F₂ lines was also genotyped with the identified markers RM 225, RM 584,RM 19429 and single marker analysis showed the probability value 0.05 in F₂ lines.