Initially, BPH2 was reported as a recessive gene12. However, Murai et al. reported that BPH2 was a dominant gene by analyzing Norin-PL4 that harbored BPH2 from IR1154-243 in the genetic background of a susceptible japonica cultivar. BPH26 has also been reported as a dominant gene11. Cultivars containing the resistance allele of BPH2, such as IR42, were bred in Southeast Asia to control BPH. However, a virulent biotype of BPH appeared, and the resistance afforded by BPH2 was gradually rendered ineffective9.