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

Introductory paragraph 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.