Analyzing sequence variation of the Avirulence Avr-Pita1 gene of rice blast isolates, Magnaporthe oryzae in Vietnam

Abstract

Rice blast disease caused by a filamentous fungus (Magnaporthe oryzae) has been one of the most devastating of all cereal diseases worldwide. The interaction between rice plant, Oryza sativa and the rice blast fungus, M. oryzae is activated by the interaction between protein products of rice resistant genes and fungal avirulence genes. The resistant genes can protect rice from infection of rice blast fungus. However, the resistant genes are usually broken down after several years due to the evolution of new fungal races. Thus, finding rice blast isolates containing the avirulence Avr-Pita1 gene and analyzing the sequence variation of this gene are necessary for further research in reducing rice blast infection. The avirulence Avr-Pita1 gene of 25 rice blast isolates collected from northern, middle and southern Vietnam were amplified and analyzed. The phylogenetic trees were constructed using neighbor-joining and maximum likelihood methods in the MEGA 6.0 program. The results showed that 18 rice blast isolates had the Avr-Pita1 gene and most of them were from middle and southern Vietnam. The results of phylogenetic analysis and polymorphism analysis also showed the diversity of the nucleotide sequence of the Avr-Pita1 gene among the 18 rice blast isolates and differences between Avr-Pita1 of Vietnamese isolates and those from other countries.