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Avirulence (AVR) Gene-Based Diagnosis Complements Existing Pathogen Surveillance Tools for Effective Deployment of

S M Selisana1, M J Yanoria1, B Quime1

  • 1First and sixth authors: Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños, Laguna, Philippines; second, third, fourth, eleventh, and twelfth authors: Genetics and Biotechnology Division, International Rice Research Institute, Los Baños, Laguna, Philippines; fourth author: Department of Genetics, Faculty of Science, Kasetsart University, Bangkok, Thailand; fifth author: The Key Laboratory of Biopesticide and Chemistry Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, China; seventh and eighth authors: Department of Plant Pathology, The Ohio State University, Columbus; ninth author: Department of Plant Pathology, University of Arkansas, Fayetteville; and tenth author: Biosciences Department, Exeter University, UK.

Phytopathology
|February 8, 2017
PubMed

Insights

A new tool uses avirulence (AVR) genes to diagnose rice blast pathogen virulence. This method precisely identifies pathogen populations and predicts resistance gene effectiveness in rice varieties.

Area of Science:

  • Plant Pathology
  • Molecular Genetics
  • Agricultural Science

Background:

  • Magnaporthe oryzae, the cause of rice blast disease, evolves by mutating avirulence (AVR) genes to evade plant resistance (R) genes.
  • Understanding pathogen virulence is crucial for developing durable disease resistance in rice.

Purpose of the Study:

  • To develop and validate an AVR-gene-based diagnostic tool for assessing the virulence spectrum of rice blast pathogen populations.
  • To correlate AVR gene frequencies with the effectiveness of R genes in differential rice lines.

Main Methods:

  • Pathotype analysis of 77 field isolates using R-gene differential lines.
  • Haplotype determination of seven AVR genes via PCR amplification and sequencing.
  • Correlation analysis between AVR gene frequencies and differential line resistance frequencies.

Main Results:

  • Twenty virulent pathotypes were identified among 77 isolates; 10 differential lines showed low resistance (<24%), 8 showed high resistance (>95%).
  • AVRPiz-t and AVR-Pii were highly frequent (100% and 84.9%), while AVR-Pik-D, AVR-Pik-E, AVRPiz-t, AVR-Pita, AVR-Pia, and AVR1-CO39 showed low or zero frequency.
  • A discrepancy in three differential lines (IRBLzt-T, IRBLta-K1, IRBLkp-K60) suggested the presence of an additional R gene, likely Pi19 or an allele.

Conclusions:

  • AVR-gene-based diagnosis offers a precise, R-gene-specific, and differential line-free method for pathogen virulence assessment.
  • This tool can predict the effectiveness of R genes in rice varieties, aiding in breeding strategies against rice blast.

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