Multiple avirulence loci and allele-specific effector recognition control the Pm3 race-specific resistance of wheat to powdery mildewopen

Salim Bourras, Kaitlin Elyse McNally, Roi Ben-David, Francis Parlange, Stefan Roffler, Coraline Rosalie Praz, Simone Oberhaensli, Fabrizio Menardo, Daniel Stirnweis, Zeev Frenkel, Luisa Katharina Schaefer, Simon Flückiger, Georges Treier, Gerhard Herren, Abraham B. Korol, Thomas Wicker, Beat Keller

Research output: Contribution to journalArticlepeer-review


In cereals, several mildew resistance genes occur as large allelic series; for example, in wheat (Triticum aestivum and Triticum turgidum), 17 functional Pm3 alleles confer agronomically important race-specific resistance to powdery mildew (Blumeria graminis). The molecular basis of race specificity has been characterized in wheat, but little is known about the corresponding avirulence genes in powdery mildew. Here, we dissected the genetics of avirulence for six Pm3 alleles and found that three major Avr loci affect avirulence, with a common locus_1 involved in all AvrPm3-Pm3 interactions. We cloned the effector gene AvrPm3a2/f2from locus_2, which is recognized by the Pm3a and Pm3f alleles. Induction of a Pm3 alleledependent hypersensitive response in transient assays in Nicotiana benthamiana and in wheat demonstrated specificity. Gene expression analysis of Bcg1 (encoded by locus_1) and AvrPm3a2/f2revealed significant differences between isolates, indicating that in addition to protein polymorphisms, expression levels play a role in avirulence. We propose a model for race specificity involving three components: an allele-specific avirulence effector, a resistance gene allele, and a pathogenencoded suppressor of avirulence. Thus, whereas a genetically simple allelic series controls specificity in the plant host, recognition on the pathogen side is more complex, allowing flexible evolutionary responses and adaptation to resistance genes.

Original languageEnglish
Pages (from-to)2991-3012
Number of pages22
JournalPlant Cell
Issue number10
StatePublished - Oct 2015

Bibliographical note

Publisher Copyright:
©2015 American Society of Plant Biologists. All rights reserved.

ASJC Scopus subject areas

  • Plant Science
  • Cell Biology


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