Abstract: Magnaporthe grisea is one of the most devastating pathogens of rice. The specific interaction between rice and M. grisea follows the gene\|for\|gene hypothesis， and the cognate genes in M. grisea were called AVR genes. When the corresponding host gene， known as resistance （R） genes recognize the products of the cognate AVR genes， the immune responses of rice which are always associated with hypersensitive response are trigged. During the interaction between M. grisea and its host， AVR genes always exhibit the characterization of instability. The mutation of AVR genes usually result in the loss of resistance of rice. The mutations of AVR genes involve several mechanisms， including point mutations， deletions, insertion, duplication and frame\|shift mutation. The mutation mechanisms of AVR1\|CO39， PWL， AVR\|Pita are well studied， the mutation pattern of other AVR genes including ACE1， AvrPiz\|t， AVR\|Pia， AVR\|Pii and AVR\|Pik/km/kp are less known and need further research.

Key words: Magnaporthe grisea, avirulence gene, mutation