The variable wheat stripe rust effector AvrYr7 evades Yr7 recognition through sequence and expression polymorphisms

Wheat provides about 20% of total dietary calories worldside ¹ . Wheat diseases, including wheat stripe (yellow) rust, cause billions of dollars in losses each year ² . Wheat stripe (yellow) rust is caused by the fungal pathogen Puccinia striiformis f. sp. tritici (Pst) which is best controlled by fungicide application and disease resistant wheat cultivars ³ . To-date, there are over 80 catalogued and >10 cloned yellow rust resistance genes ( Yr genes) ⁴ . Yet our knowledge of corresponding avirulence ( Avr ) genes lags far behind ^5–8 . The absence of cloned Avrs reflects Pst’s complex genome and the lack of robust transformation and genetic systems ³ . Recent advances in generating high-quality genome assemblies and the development of wheat defense assays have addressed these challenges ^9–11 . Here we clone AvrYr7 which is recognized by Yr7 ¹² . We further identify six additional alleles of AvrYr7 that escape recognition due to non-synonymous genetic variations, transposable element activity, missense mutation, and expression polymorphism. These findings provide critical insights into virulence evolution in one of the world’s most important wheat pathogens.