Abstract: The Pik locus, located on the long arm of chromosome 11, is a hotspot region for rice blast resistance. To study the diversity and distribution of the resistance (R) genes at the Pik locus will be useful for revealing the evolutionary mechanisms of this gene and to further explore its alleles. We sequenced and analyzed the Pik-2 coding region of 400 Oryza glaberrima and 400 Oryza sativa cultivars from different countries and regions. 113 and 78 polymorphic sites were found in O. glaberrima and O. sativa, respectively, which showed high mutation frequency at the nucleotide position 1879. According to the characteristics of the base variations, 17 haplotypes of O. glaberrima and 12 haplotypes of O. sativa were identified. The results indicated that the Pik-2 haplotype distribution in O. glaberrima was characterized by large aggregation and small dispersion, in contrast to the very extensive distribution in O. sativa. Phylogenetic analysis of different haplotypes showed that most groups contained both African and Asian rice haplotypes, suggesting that African and Asian rice had similar haplotypes in the Pik-2 LRR domain during their independent evolution.

Key words: Oryza glaberrima, Oryza sativa, rice blast, resistance gene, Pik-2