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ARS Home » Southeast Area » Stuttgart, Arkansas » Dale Bumpers National Rice Research Center » Research » Publications at this Location » Publication #346522
Title: Selection and Mutation of the Avirulence Gene AVR-Pii of the Rice Blast Fungus Magnaporthe Oryzae

Author
item LU, LIN - Yunan Academy Of Agricultural Sciences
item LI, CHENGYUN - Yunan Academy Of Agricultural Sciences
item FAN, HUACAI - Yunan Academy Of Agricultural Sciences
item Jia, Yulin
item LI, JINBIN - Yunan Academy Of Agricultural Sciences

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2018
Publication Date: 8/22/2018
Citation: Lu, L., Li, C., Fan, H., Jia, Y., Li, J. 2018. Selection and mutation of the avirulence Gene AVR-Pii of the rice blast fungus magnaporthe oryzae. Plant Pathology. https://doi: 10.1111/ppa.12935.
DOI: https://doi.org/10.1111/ppa.12935

Interpretive Summary: Rice blast resistance (R) gene Pii is effective in preventing infections of the fungus Magnaporthe oryzae isolates that contain the cognate avirulence (AVR) gene AVR-Pii. In the present study, we analyzed DNA sequences of the AVR gene, AVR-Pii, in M. oryzae isolates purified from rice fields in Yunnan province to identify mutations in AVR-Pii that will cause the fungus to infect rice varieties with Pii. Genomic DNA of 454 isolates of M. oryzae collected from Yunnan was used for PCR amplification with AVR-Pii specific primers. Results showed that 82 isolates of M. oryzae carried AVR-Pii suggesting that Pii is effective for these isolates. Three AVR-Pii haplotypes, encoding two novel AVR-Pii variants, were identified. All DNA sequence variations occurred in the protein coding region resulting in changes of the proteins. Among them, a single nucleotide change in one AVR-Pii haplotype was correlated with disease susceptibility of rice varieties with Pii. These results suggest that AVR-Pii is under selection pressure and mutations in AVR-Pii are responsible for defeating race-specific resistance in nature. This knowledge is useful to predict the effectiveness of blast resistance mediated by the rice R gene Pii.

Technical Abstract: Magnaporthe oryzae avirulence genes are predicted to be involved in pathogen invasion and their virulence function are restricted by the presence of cognate resistance genes. In this study, we analyzed DNA sequences of the avirulence gene, AVR-Pii, in field isolates of M. oryzae to understand haplotype diversity of AVR-Pii under field conditions in China. Genomic DNA of 454 isolates of M. oryzae collected from Yunnan province of China was used for PCR amplification to examine the existence of AVR-Pii using gene-specific PCR markers. Results of PCR products showed that 82 isolates of M. oryzae carried AVR-Pii. Among them, 35.5%, 9.7%, 13.3%, 15.2%, 14.3%, and 12.8% of M. oryzae carried AVR-Pii from central, northeastern, northwest, southeast, southwestern, and western of Yunnan province, respectively. The detection rate of AVR-Pii was in order as: central>southeast>southwestern>northwest>western>northeastern of Yunnan province. Moreover, a total of three AVR-Pii haplotypes encoding two novel AVR-Pii variants were identified among 55 isolates. All DNA sequence variation was found to occur in the protein coding region resulting in amino acid substitution. One virulent haplotype of AVR-Pii to Pii was identified among the 55 field isolates. The AVR-Pii gene has evolved to virulence from avirulent origins via base substitution. These findings demonstrate that AVR-Pii is under positive selection and mutations of AVR-Pii are responsible for defeating race-specific resistance in nature.