Emergence of Rice Blast AVR-Pi9 Resistance Breaking Haplotypes in Yunnan Province, China.

The rice blast disease (caused by ) is a devastating disease in China. Understanding the molecular mechanisms of interaction for the cognate avirulence () gene with host resistance () genes, as well as their genetic evolution is essential for sustainable rice production. In the present study, we conducted a high-throughput nucleotide sequence polymorphism analysis of the gene that was amplified from the rice-growing regions of the Yunnan Province in China. We detected the presence of seven novel haplotypes from 326 rice samples. In addition, the sequences of were also obtained from two non-rice hosts, and . The sequence analysis revealed the insertions and deletions in the coding and non-coding regions of the gene. The pathogenicity experiments of these haplotypes on previously characterized monogenic lines showed that the newly identified haplotypes are virulent in nature. The breakdown of resistance was attributed to the development of new haplotypes. Our results suggest that the mutation in the gene is an alarming situation in the Yunnan province and thus needs attention.