Virulence Structure of f. sp. and Effectiveness of Resistance Genes in Poland During 2017-2019.

Crown rust caused by f. sp. is one of the most destructive diseases of oat, regularly occurring worldwide and leading to significant yield losses. This article characterizes the pathotype structure of in Poland and evaluates the potential of crown rust race-specific resistance genes for use in practical breeding conditions in this region. A total of 466 isolates were derived from four locations of intensive oat breeding in Poland in 2017 to 2019, representing populations from West, East, South, and Central Poland. Their virulence structure was determined on 35 differential lines in laboratory conditions. In each year and location, high pathotype diversity was observed. In total, 347 (75%) pathotypes were detected. On average isolates collected in 2017 and 2018 were virulent to 11% of the oat differentials. In 2019 isolates from East and South of Poland were able to overcome 18.3 and 18.5% of the oat differentials, respectively. There was no isolate virulent against , , and crown rust resistance genes. isolates displayed modest virulence levels, high diversity, and no prevailing pathotype. The information provided here may be helpful for development of resistance breeding strategies and in choosing the most effective major genes for pyramiding into cultivars.