Molecular identification and virulence analysis of AVR genes in rice blast pathogen, Magnaporthe oryzae from Eastern India

Abstract

A set of 63 rice blast pathogen, Magnaporthe oryzae isolates from different cultivars in different rice growing regions of Eastern India was surveyed for the presence of nine known avirulence genes, Avr-Piz-t, Avr-Pita, ACE1, Avr-Pia, Avr-Pit, Avr1-CO39, Avr-Pi7, Avr-Pi15 and Avr-Pik with gene-specific molecular markers. These genes were detected with varying frequencies. Avr-Piz-t and Avr-Pik had the highest frequency (100 %) while Avr1-CO39 had the lowest (2 %). Frequencies of other Avr genes varied from 38 to 86 %. Spatial distribution analysis revealed almost uniform distribution of Avr genes in Eastern India. Out of 63 isolates, seven possessed the maximum of eight Avr genes, while a minimum of only two Avr genes were detected in another set of five isolates. Virulence analyses of 47 isolates revealed that many isolates possessing alleles of Avr genes were able to infect monogenic lines harbouring cognate R genes suggesting that such isolates might possess alternate mechanisms to escape host surveillance.