Pike, a rice blast resistance allele consisting of two adjacent NBS-LRR genes, was identified as a novel allele at the Pik locus

Rice (Oryza sativa L.) blast caused by fungus Magnaporthe oryzae is one of the most devastating diseases throughout the world. In the current study, a rice blast resistance gene, designated as Pike, was identified from an indica breeding line Xiangzao143 conferring a durable resistance to rice blast. A map-based cloning strategy was then employed to locate Pike to a 306-kb genomic interval in proximity of the telomeric region of the long arm of chromosome 11. Candidate gene analysis and transgenic complementation test demonstrated that two Xiangzao143-derived adjacent CC-NBS-LRR genes (Pike-1 and Pike-2) at the previously identified Pik locus were required for the Pike-mediated resistance. As compared to the previously identified Pik alleles, the putative Pike-1 peptide was found to be unique in three highly polymorphic sites, two amino acid residue sites (D153 and D229) in the CC domain and one site (L442-W443-P465) in the NBS domain. In addition, against a set of 215 M. oryzae isolates collected from diverse rice cropping areas of China, the Pike carrier Xiangzao143 showed a unique resistance spectrum and a high resistance frequency of 86.1 %. These results thus declared Pike as a novel allele of the Pik locus. Two SNPs G1328C and A3017T in Pike DNA sequence were identified and based on the SNPs, two Pike-specific dCAPS markers d-G1328C and d-A3017T were developed and have been used to effectively distinguish Pike from all of the previously identified Pik alleles.