Genetic interaction between Bph50 and Bph51 confers resistance to brown planthopper in rice

Rice serves as the primary food source for over half the world's population, making its stable production is critical for global food security. The brown planthopper (BPH, Nilaparvata lugens Stål.) ranks among the most devastating rice pests worldwide. Developing BPH-resistant varieties through resistance gene discovery represents the most sustainable control strategy. Our study identified two novel resistance loci, Bph50 and Bph51, through analysis of the resistant wild rice germplasm GXU184 using BSA-seq and QTL mapping. Interestingly, neither locus of Bph50 or Bph51 alone conferred resistance; rather, their combined presence in lines restored the high resistance observed in GXU184. Fine mapping localized Bph50 to a 270 kb region (6.732-7.003 Mb) on chromosome 4S and Bph51 to a 700 kb interval (15.035-15.735 Mb) on chromosome 4L. We developed a near-isogenic line (NIL) 9311Bph50/Bph51 carrying both loci through marker-assisted selection, which exhibited strong BPH resistance without compromising agronomic performance. Transcriptomic analysis revealed that the resistance mechanism involves coordinated upregulation of genes related to cellulose biosynthesis in leaf sheaths. This enhancement of cell wall components likely increases tissue rigidity, creating a physical barrier that impedes BPH stylet penetration during feeding. Our findings reveal a novel resistance mode in which Bph50 and Bph51 confer BPH resistance by genetically interacting.