Sequence variation of avirulence gene AVR-Pita1 in rice blast fungus, Magnaporthe oryzae

Abstract

The interaction between rice, Oryza sativa, and rice blast fungus, Magnaporthe oryzae, is triggered by an interaction between the protein products of the host resistant gene, and the pathogen avirulence gene. This interaction follows the ‘gene-for-gene' concept. The resistant gene has effectively protected rice plants from rice blast infection. However, the resistant genes usually break down several years after the release of the resistant rice varieties because the fungus has evolved to new races. The objective of this study is to investigate the nucleotide sequence variation of the AVR-Pita1 gene that influences the adaption of rice blast fungus to overcome the resistant gene, Pi-ta. Thirty rice blast fungus isolates were collected in 2005 and 2010 from infected rice plants in northern and northeastern Thailand. The nucleotide sequences of AVR-Pita1 were amplified and analyzed. Phylogenetic analysis was conducted using the MEGA 5.0 program. The results showed a high level of nucleotide sequence polymorphisms and the positive genetic selection pressure in Thai rice blast isolates. The details of sequence variation analysis were described in this article. The information from this study can be used for rice blast resistant breeding program in the future.