Using virulence mutants to identify Avr genes in the wheat stem rust fungus, Puccinia graminis f. sp. tritici

C2 - Non-edited contributions to conferences

Dodds, P., Upadhyaya, N., Ortiz, D., Li, F., Chen, J., Miller, M., Luo, M., Mago, R., Ellis, J., Sperschneider, J., Nguyen-Phuc, H., Bouton, C., Steffenson, B., Hirsch, C., Silverstein, K., Park, R., Kanyuka, K. and Figueroa, M. 2019. Using virulence mutants to identify Avr genes in the wheat stem rust fungus, Puccinia graminis f. sp. tritici. 30th Fungal Genetics Conference. Pacific Grove, California, USA 12 Mar 2019

AuthorsDodds, P., Upadhyaya, N., Ortiz, D., Li, F., Chen, J., Miller, M., Luo, M., Mago, R., Ellis, J., Sperschneider, J., Nguyen-Phuc, H., Bouton, C., Steffenson, B., Hirsch, C., Silverstein, K., Park, R., Kanyuka, K. and Figueroa, M.
TypeC2 - Non-edited contributions to conferences
Abstract

The wheat stem rust fungus Puccinia graminis f. sp. tritici (Pgt) is one of the most destructive pathogens of wheat. Resistance of host lines is often governed by recognition of fungal effector proteins (avirulence/virulence proteins) by plant resistance proteins (R proteins). We have taken a mutational genomics approach to identify Avr genes in Pgt. We isolated spontaneous mutants with virulence for Sr50, Sr5, Sr27, Sr21 or Sr45 by selection on resistant host lines. Sequence analysis of the Sr50 virulent mutant revealed that virulence resulted from the exchange of a whole chromosome between the two haploid nuclei of this dikaryotic organism, resulting in loss of the avirulence allele. This confirms the important role of somatic exchange events in virulence evolution in Pgt. The AvrSr50 gene was identified from the 25 candidate effector genes from this chromosome by transient co-expression with the cloned Sr50 gene in N. benthamiana. AvrSr50 recognition was confirmed in wheat by viral expression. Recognition of the AvrSr50 protein by the host Sr50 immune receptor is based on direct interaction and we have identified critical amino acid polymorphisms contributing to the escape from recognition in virulent isolates. Identification of AvrSr50 has enabled development of tools for testing effector function in wheat including viral overexpression and wheat protoplast transient expression assays. Spontaneous mutants for several other Avr loci have also been sequenced and a new Pacbio-based genome assembly for the Australian parental Pgt isolate has facilitated the delineation of these loci. Three mutants with virulence for Sr27 contain overlapping deletions and a single candidate gene for AvrSr27 has been identified. Likewise, AvrSr5 mutants contain large deletions spanning several candidate effector genes.

KeywordsWheat; Stem rust; Effector; Disease resistance; Virulence
Year of Publication2019
Conference title30th Fungal Genetics Conference
Conference locationPacific Grove, California, USA
Event date12 Mar 2019
17 Mar 2019
Open accessPublished as bronze (free) open access
Web address (URL) of conference proceedingshttp://conferences.genetics-gsa.org/Fungal/2019/pdf/Fungal19_Program_Abstract_Book_v2.pdf
Funder project or codeDFW - Designing Future Wheat - Work package 2 (WP2) - Added value and resilience
FunderBiotechnology and Biological Sciences Research Council
Accepted author manuscript
Output statusPublished
Publication dates
Print12 Mar 2019
Copyright licenseOther

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