Identification of a novel planthopper resistance gene from wild rice (Oryza rufipogon Griff.)

Rice planthoppers, including brown planthopper (BPH) and white-backed planthopper (WBPH), are the most destructive pests in Asian rice cultivation regions. Planthopper resistance genes that have been mapped and characterized advance our understanding of underlying resistance mechanisms and facilitate the breeding of resistant varieties, thereby contributing to an efficient pest management strategy. In this study, a novel resistance gene Bph38 derived from the wild rice species Oryza rufipogon Griff. was found to confer high resistance to BPH and WBPH. Conventional mapping was performed to identify regions associated with BPH and WBPH resistance, and two mapping efforts led to the same region on chromosome 4 flanked by markers RM16563 and RM16763. Bulked-segregant analysis and next-generation sequencing were performed using the same population to detect the resistance gene. Conventional mapping narrowed the region to a 12.3-Mb segment, and fine mapping using BC₁F₂ recombinants identified a 79-kb segment flanked by markers YM112 and YM190. Near-isogenic lines (NILs) carrying Bph38 in the 9311 (indica) and BR54 (japonica) genetic backgrounds were developed by crossing and backcrossing with marker-assisted selection. The agronomic traits and BPH and WBPH resistance of the NILs were similar to those of the recurrent parents. Mandatory feeding and host-choice tests revealed that Bph38 showed both antibiotic and antixenotic effects in both insects, with stronger effects in indica-background lines. Further fine mapping and characterization of the major gene may result in map-based cloning of the gene and allow its application in breeding insect-resistant rice varieties.