Effector Genes in Magnaporthe oryzae Triticum as Potential Targets for Incorporating Blast Resistance in Wheat

Monica Navia-Urrutia, Gloria Mosquera, Rebekah Ellsworth, Mark Farman, Harold N. Trick, Barbara Valent

Research output: Contribution to journalArticlepeer-review

Abstract

Wheat blast (WB), caused by Magnaporthe oryzae Triticum pathotype, recently emerged as a destructive disease that threatens global wheat production. Because few sources of genetic resistance have been identified in wheat, genetic transformation of wheat with rice blast resistance genes could expand resistance to WB. We evaluated the presence/absence of homologs of rice blast effector genes in Triticum isolates with the aim of identifying avirulence genes in field populations whose cognate rice resistance genes could potentially confer resistance to WB. We also assessed presence of the wheat pathogen AVR-Rmg8 gene and identified new alleles. A total of 102 isolates collected in Brazil, Bolivia, and Paraguay from 1986 to 2018 were evaluated by PCR using 21 pairs of gene-specific primers. Effector gene composition was highly variable, with homologs to AvrPiz-t, AVR-Pi9, AVR-Pi54, and ACE1 showing the highest amplification frequencies (>94%). We identified Triticum isolates with a functional AvrPiz-t homolog that triggers Piz-t–mediated resistance in the rice pathosystem and produced transgenic wheat plants expressing the rice Piz-t gene. Seedlings and heads of the transgenic lines were challenged with isolate T25 carrying functional AvrPiz-t. Although slight decreases in the percentage of diseased spikelets and leaf area infected were observed in two transgenic lines, our results indicated that Piz-t did not confer useful WB resistance. Monitoring of avirulence genes in populations is fundamental to identifying effective resistance genes for incorporation into wheat by conventional breeding or transgenesis. Based on avirulence gene distributions, rice resistance genes Pi9 and Pi54 might be candidates for future studies.

Original languageEnglish
Pages (from-to)1700-1712
Number of pages13
JournalPlant Disease
Volume106
Issue number6
DOIs
StatePublished - Jun 2022

Bibliographical note

Funding Information:
We thank Guo-Liang Wang (The Ohio State University) for providing us with the Piz-t expression vector pPiz-t_C1305 used in our study. We thank Giovana Cruppe, Sanzhen Liu, Tyler Suelter, and Melinda Dalby (Kansas State University) for sharing unpublished M. oryzae genome data and unpublished data on diagnostic marker status for some strains. We thank Hyeonju Lee and Neerja Tyagi for their support in the wheat transformation experiments. We thank Gary Peterson (FDWSRU, Fort Detrick, MD, U.S.A.), Paulo Kuhnem (Biotrigo Genética, Brazil), and others for providing strains listed in Supplementary Table S1. The first author also thanks the Colombian Ministry of Sciences, Technology and Innovation (MinCiencias) for partially supporting her academic program.

Funding Information:
This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2013-68004-20378 from the USDA National Institute of Food and Agriculture. This is contribution no. 22-065-J from the Kansas Agricultural Experiment Station. We thank Guo-Liang Wang (The Ohio State University) for providing us with the Piz-t expression vector pPiz-t_C1305 used in our study. We thank Giovana Cruppe, Sanzhen Liu, Tyler Suelter, and Melinda Dalby (Kansas State University) for sharing unpublished M. oryzae genome data and unpublished data on diagnostic marker status for some strains. We thank Hyeonju Lee and Neerja Tyagi for their support in the wheat transformation experiments. We thank Gary Peterson (FDWSRU, Fort Detrick, MD, U.S.A.), Paulo Kuhnem (Biotrigo Genética, Brazil), and others for providing strains listed in Supplementary Table S1. The first author also thanks the Colombian Ministry of Sciences, Technology and Innovation (MinCiencias) for partially supporting her academic program.

Funding Information:
Funding: This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2013-68004-20378 from the USDA National Institute of Food and Agriculture. This is contribution no. 22-065-J from the Kansas Agricultural Experiment Station.

Publisher Copyright:
© 2022 The American Phytopathological Society

Keywords

  • avirulence gene
  • genetic transformation of wheat
  • Magnaporthe oryzae Triticum pathotype
  • resistance gene
  • wheat blast

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science

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