An Avirulence Gene Cluster in the Wheat Stripe Rust Pathogen (Puccinia striiformis f. sp. tritici) Identified through Genetic Mapping and Whole-genome Sequencing of a Sexual Population

Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe (yellow) rust, is an absolute, biotrophic fungus. It was difficult to study the genetics of the pathogen due to the lack of sexual reproduction. The recent discovery of alternate hosts for the rust fungus makes it possible to study the inheritance and map genes involved in its interaction with its host plants. To identify Avr genes in Pst, we developed a segregating population by self-fertilizing isolate 12-368 (race PSTv-4) on barberry (Berberis vulgaris) plants under controlled conditions. Virulence testing of the progeny isolates showed segregation on nine wheat resistance genes and confirmed that the inheritance of avirulence/virulence phenotype is isolate-dependent. The 117 progeny isolates were whole-genome sequenced at >30X coverage using the Illumina HiSeq PE 150 technology.