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 in Asia. 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 (Oryza rufipogon) 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 177 kb region (6.732-6.909 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) 9311^Bph50/Bph51 carrying both loci through marker-assisted selection (MAS), which exhibited strong BPH resistance without compromising agronomic performance. Integrated transcriptomic and histological analyses indicate that this resistance mechanism involves the coordinated upregulation of cellulose biosynthesis-related genes and the accumulation of polysaccharides such as cellulose in leaf sheaths. This enhancement of cell wall components likely increases tissue rigidity, forming a physical barrier that impedes stylet penetration during BPH feeding. Our findings unveil a novel resistance mechanism in which Bph50 and Bph51 genetically interact to confer BPH resistance, providing valuable insights for breeding durable pest-resistant rice varieties.