First detailed report on Puccinia graminis f. sp. avenae virulence structure and Pg resistance genes effective in Poland

Occurrence of stem rust, caused by Puccinia graminis f. sp. avenae, on oat fields in Europe may lead to significant yield losses. The last P. graminis virulence research in this region had been carried out in the years 1988 to 1996, therefore the aim of this study was the update of pathogen’s virulence structure as well as the evaluation of Pg race-specific resistance genes and their potential for use in practical breeding in central and eastern European growing conditions. To assess the pathotype structure of P. graminis in Poland and evaluate the potential of Pg resistance genes, 148 isolates were collected during 2017–2020. Their virulence structure was determined in laboratory conditions on 12 Pg differentials as well as oat lines ‘Pg-a’, ‘Alpha’, ‘Omega’ and ‘Wisconsin X-1588-2’. In total, 57 pathotypes were detected, of which the most dominant race was SSK. High frequency was also recorded for TSK, TKK and TTK. Puccinia graminis isolates were able to overcome from 5 to 11 Pg resistance genes with an average virulence complexity of 8.6. There was no isolate virulent to Pg12, ‘Pg-a’, ‘Alpha’ and ‘Omega’, hence these genes can be used in the breeding programmes. Gene Pg10 was also relatively effective, overcome by 33 out of 148 P. graminis isolates. The virulence profile observed may be representative of eastern Europe and beyond.