The evolution and global diversity of AvrPm3a2/f2 and SvrPm3a1/f1, two effector genes controlling race-specific resistance in wheat powdery mildew
K. MCNALLY (1), S. Bourras (2), F. Menardo (2), C. Praz (2), B. Keller (2) (1) University of Zurich Institute for Plant and Microbial Biology, Switzerland; (2) University of Zurich Institute of Plant and Microbial Biology, Switzerland

The allelic series of the Pm3 NBS-LRR gene confers race specific resistance to wheat powdery mildew. Despite remarkable sequence identity (>97%) these alleles recognize distinct spectra of pathogen races. Recently we reported the genetic basis of the Pm3 race-specific avirulence on the pathogen side, and the cloning of AvrPm3a2/f2, the first avirulence effector in powdery mildews. Recognition of AvrPm3a2/f2 by the Pm3a and Pm3f alleles induces a hypersensitive cell-death response that halts pathogen invasion. We cloned another effector, SvrPm3a1/f1, involved in the suppression of this recognition. We found that the outcome of the Avr-R-Svr interaction depends on sequence polymorphisms and expression levels differentiating active vs. inactive AVR and SVR effector proteins. Currently we are studying the AvrPm3a2/f2 locus to answer questions about the evolution of effectors and Avrs in powdery mildew, as well as the mechanisms that regulate their expression. We have defined the Avr effector gene family, their expression pattern in isolates with different virulence profiles, and tested conserved structural motifs for their individual contributions to recognition by Pm3a and Pm3f. Using isolates collected from the US, UK, France, Switzerland, Israel, China, Japan and Australia, we aim to study the naturally occurring haplotypes of AvrPm3a2/f2 and SvrPm3a1/f1, their expression patterns, and their relative contribution to the incidence of virulence and avirulence to Pm3a/f globally.

Abstract Number: P17-571
Session Type: Poster