QTL Mapping for Brown Planthopper Resistance Reveals a Major Stable QTL on Chromosome 4 From Oryza nivara IRGC81848

The brown planthopper (BPH), Nilaparvata lugens Stål, is one of the most devastating pests of rice ( Oryza sativa L.), leading to significant annual yield losses. Host plant resistance offers a sustainable and eco‐friendly strategy for BPH management. In this study, a population in the BC 2 F 8 generation, derived from the wild species Oryza nivara (IRGC81848) as the donor and the susceptible popular variety Swarna, was used as the mapping population to identify BPH‐resistant lines. This mapping population was screened over multiple years to identify resistant donors and to detect genomic regions associated with BPH and WBPH resistance. Based on damage scores, NPS55 (222S), NPS50 (212S), NPS17 (122S), NPS70 (24S), NPS61 (230S) and NPS57 (227S) exhibited consistently resistant reactions over the years, and NPS61 (230S) showed resistance to both BPH and WBPH populations. A total of 14 quantitative trait loci (QTL) were identified over 5 years of evaluation (2016, 2017, 2018, 2020 and 2021). Notably, a consistent QTL, qBPH_4.1 , was identified across four testing environments and the overall average, explaining 17.37%–42.46% of phenotypic variation, which harbours genes encoding extracellular LRR‐EGF domain proteins. Three distinct QTLs were identified on chromosome 2 ( qBPH2016_2.1 , qBPH2017_2.3 and qBPH2018_2.2 ), with phenotypic variance ranging from 5.66% to 11.22%. In 2018, two major QTLs were detected, qBPH2018_8.1 and qBPH2018_9.1 , with PVEs of 11.7% and 13.7%, respectively. Resistant genotypes harboured QTLs originating from O. nivara , which contributed to reduced BPH susceptibility scores, indicating the presence of a favourable allele from wild species. These findings highlight the potential of wild rice germplasm to enhance BPH resistance and to provide valuable prebreeding materials for future crop improvement programs aimed at developing BPH‐resistant rice cultivars.