ARS | Publication request: Pathological and Molecular Characterization of Rice Blast Pathogenicity Factor AVR-Pita 1 in Field Isolates

Submitted to: Annual International Plant & Animal Genome Conference
Publication Type: Experiment Station
Publication Acceptance Date: May 30, 2012
Publication Date: August 3, 2012
Citation: Jia, Y., Correll, J.C., Lee, F.N. 2012. Pathological and Molecular Characterization of Rice Blast Pathogenicity Factor AVR-Pita 1 in Field Isolates. Annual International Plant & Animal Genome Conference. Page 53-72 in b.R. Wells Rice Research Studies 2011.

Interpretive Summary: The rice blast resistance gene Pi-ta has been effective in managing rice blast disease in Arkansas and the Southern US. The AVR-Pita1 gene in the pathogen, Maganporthe oryzae, encodes a metalloprotease that determines the efficacy of Pi-ta mediated blast resistance. Analysis of genetic variation of AVR-Pita1 in field isolates of the pathogen has lead to a better understanding of the stability of rice blast resistance. In the present study, race identity in 126 field blast isolates was determined, the AVR-Pita1 alleles were sequenced, and pathogenicity toward cultivars containing Pi-ta and lacking Pi-ta was determined. It was found that most of sequence variation in AVR-Pita1 results in altered metalloproteases in avirulent isolates. However, in isolates that attack Pi-ta resistance gene, AVR-Pita1 metalloproteases were found to be “destroyed” through various genetic mechanisms. For the first time, we provided evidence to demonstrate molecular mechanisms of the instability of rice blast resistance and the evolution of virulence in the pathogen.

Technical Abstract: The rice blast resistance gene Pi-ta has been effective in managing rice blast disease in Arkansas and the Southern US. The AVR-Pita1 gene in the pathogen, Maganporthe oryzae, encodes a metalloprotease that determines the efficacy of Pi-ta mediated blast resistance. Analysis of genetic variation of AVR-Pita1 in field isolates of the pathogen has lead to a better understanding of the stability of rice blast resistance. In the present study, race identity in 126 field blast isolates was determined, the AVR-Pita1 alleles were sequenced, and pathogenicity toward cultivars containing Pi-ta and lacking Pi-ta was determined. It was found that most of sequence variation in AVR-Pita1 results in altered metalloproteases in avirulent isolates. However, in isolates that attack Pi-ta resistance gene, AVR-Pita1 metalloproteases were found to be “destroyed” through various genetic mechanisms. For the first time, we provided evidence to demonstrate molecular mechanisms of the instability of rice blast resistance and the evolution of virulence in the pathogen.