Genetic and physical mapping of a new rice blast resistance specificity Pi-67 from a broad spectrum resistant genotype Tetep

Abstract

The Vietnamese rice landrace Tetep is known world-wide for its exceptional broad-spectrum and durable resistance to blast disease caused by Pyricularia oryzae. In present study, we report on identification and mapping of a new blast resistance gene Pi-67 from a doubled haploid line TDH251 that derives its resistance from Tetep. Using a multipronged mapping strategy combining bulked segregant analysis, recessive class approach and conventional pathotype analysis, the resistance gene was fine mapped to a 0.4 cM interval flanked by markers YL87/155 and RRS8 near the centromere of chromosome 12. By projecting the sequences of flanking markers on the reference sequence of cv. Nipponbare, a 2.03 Mb region extending from position 10.60 to 12.63 Mb near the centromere of rice chromosome 12 was delineated as the region of blast resistance locus. A total of 106 predicted genes were identified in Pi-67 region by surveying the equivalent genomic region of cv. Nipponbare in Rice Annotation Project Database (RAP-DB) ( http://rapdbbeta.dna.affrc.go.jp ). Out of these, Os12g0281600 encoding nucleotide-binding site and leucine-rich repeat (NBS–LRR) protein was short listed as a potential candidate for the blast resistance gene identified from TDH251. Based on conventional pathotype analysis and allele sequencing, Pi-67(t) could be differentiated from other two blast resistance genes Pi19 and Pi-42(t) that occupy syntenic position on chromosome 12. The physical localization of Pi-67 and identification of a NBS–LRR gene Os12g0281600 as a potential R-gene candidate has set the stage for cloning and functional characterization of this resistance gene.