Virulence Structure and Diversity of Puccinia coronata f. sp. avenae P. Syd. & Syd. in Poland During 2013 to 2015.

The crown rust fungus Puccinia coronata f. sp. avenae P. Syd. & Syd. (Pca) attacks cultivated oat and its wild relatives, causing significant losses to the crop worldwide. Although understanding the origin and dynamics of the pathogen's diversity is critical to developing methods for its control, there are little relevant data on Pca virulence diversity in Europe, the global center of oat production. The goal of this study was to analyze the diversity of Pca populations in Poland in 2013 to 2015 based on their ability to overcome currently available host resistance Pc genes. Pca isolate virulence was evaluated on a panel of lines containing 26 major resistance genes of oat. The isolates were able to overcome from 1 to 16 resistance genes each, with most isolates being virulent on five to seven lines. In all years, a very high level of crown rust pathotype diversity was observed, with Simpson and Evenness indices of 0.99. In total, 156 different pathotypes were detected, with no prevalent pathotype in any of the 3 years analyzed. The results showed that the virulence level of P. coronata isolates was relatively low for each year studied (21% on average), most likely owing to the low take up of Pc genes in Polish oat cultivars, meaning that many sources of resistance are still effective against Pca races occurring in Poland. The long-range dispersal of Puccinia spores supported by the availability of wild, weedy, and cultivated Avena species makes it likely that the virulence profile seen in Poland is representative of much of central Europe and beyond.