Development of near-isogenic lines for BPH25(t) and BPH26(t), which confer resistance to the brown planthopper, Nilaparvata lugens (Stål.) in indica rice 'ADR52'

The brown planthopper [BPH; Nilaparvata lugens (Stål.)] is one of the most destructive insect pests in Asian rice-growing areas. Two genes conferring resistance to BPH, BPH25(t) and BPH26(t) derived from a BPHresistant indica rice cultivar, Oryza sativa ADR52, have been identified. However, they are linked to genes conferring late heading and hybrid spikelet sterility. To eliminate these unfavorable traits (linkage drag), we generated BC₆F₁ populations carrying BPH25(t) or BPH26(t) in a BPH-susceptible japonica cultivar, Taichung 65, through marker-assisted selection. We selected three near-isogenic lines (NILs) carrying BPH25(t) without late heading date and one NIL carrying BPH26(t) without spikelet sterility from BC₆F₂ progeny that showed between 96.3 and 99.8% of the Taichung 65 genetic background through whole-genome survey. In antibiosis testing, the rates of surviving insects and of females with swollen abdomens were lower on the NILs than on Taichung 65, indicating that bph25(t) and Bph26(t) alleles from ADR52 controlled the resistance to BPH. The NILs will serve as useful resources for (1) monitoring BPH virulence and for (2) increasing resistance to BPH.