Abstract: Rice blast, caused by the fungus Magnaporthe oryzae, reduces rice yields by 10% to 35%. Incorporating plant blast resistance genes into breeding programs is an effective strategy to combat this disease. Understanding the genetic variants that confer resistance is crucial to this strategy. The gene Bsr-d1 encodes a C₂H₂-like transcription factor, and its recessive allele confers broad-spectrum resistance against infections by various strains of M. oryzae. In this study, we investigated the molecular evolution of the rice blast resistance gene bsr-d1 in a representative population consisting of 827 cultivated and wild rice varieties. Our results revealed that wild rice exhibited significantly higher nucleotide diversity, with polymorphic regions primarily concentrated in the promoter region, in contrast to indica and japonica rice varieties. The Bsr-d1 gene displayed significant differentiation between indica and japonica, with the bsr-d1 resistance allele being unique to indica. Haplotype network and phylogenetic analyses suggested that the bsr-d1 resistance allele most likely originated from Oryza nivara in the region adjacent to the Indian Peninsula and the Indochina Peninsula. Moreover, we explored the utilization of bsr-d1 resistance alleles in China and designed a pair of DNA primers based on the polymorphic sites for the detection of the bsr-d1 resistance gene. In summary, our study uncovering the origin and evolution of bsr-d1 will enhance our comprehension of resistance gene variation and expedite the resistance breeding process.

Key words: broad-spectrum resistance, bsr-d1 gene, evolution, Magnaporthe oryzae, resistance rice breeding