Comparative genomics identifies the Magnaporthe oryzae avirulence effector AvrPi9 that triggers Pi9‐mediated blast resistance in rice

Summary We identified the M agnaporthe oryzae avirulence effector A vr P i9 cognate to rice blast resistance gene P i9 by comparative genomics of requisite strains derived from a sequential planting method. AvrPi9 encodes a small secreted protein that appears to localize in the biotrophic interfacial complex and is translocated to the host cell during rice infection. AvrPi9 forms a tandem gene array with its paralogue proximal to centromeric region of chromosome 7. AvrPi9 is expressed highly at early stages during initiation of blast disease. Virulent isolate strains contain M g‐ SINE within the A vr P i9 coding sequence. Loss of A vr P i9 did not lead to any discernible defects during growth or pathogenesis in M . oryzae . This study reiterates the role of diverse transposable elements as off‐switch agents in acquisition of gain‐of‐virulence in the rice blast fungus. The prevalence of A vr P i9 correlates well with the avirulence pathotype in diverse blast isolates from the P hilippines and C hina, thus supporting the broad‐spectrum resistance conferred by P i9 in different rice growing areas. Our results revealed that P i9 and P iz‐t at the P i2/9 locus activate race specific resistance by recognizing sequence‐unrelated A vr P i9 and A vr P iz‐t genes, respectively.