Virulence patterns of oat crown rust in Australia - season 2022

Abstract

AbstractPuccinia coronataf. sp.avenae(Pca) is an important foliar pathogen of oat which causes crown rust disease. The virulence profile of 48Pcaisolates derived from different locations in Australia was characterised using a collection of oat lines often utilised in rust surveys in the USA and Australia. This analysis indicates thatPcapopulations in Eastern Australia are broadly virulent, in contrast to the population in Western Australia (WA). Several oat lines/Pcgenes are effective against all rust samples collected from WA, suggesting they may provide useful resistance in this region if deployed in combination. We identified 19 lines from the USA oat differential set that display disease resistance toPcain WA, some in agreement with previous rust survey reports. We adopted the 10-letter nomenclature system to define oat crown rust races in Australia and compare the frequency of those virulence traits to published data from the USA. Based on this nomenclature, 42 unique races were detected among the 48 isolates, reflecting the high diversity of virulence phenotypes forPcain Australia. Nevertheless, thePcapopulation in the USA is substantially more broadly virulent than that of Australia. Close examination of resistance profiles for the oat differential set lines after infection withPcasupports hypotheses of allelism or redundancy amongPcgenes or the presence of several resistance genes in some oat differential lines. These findings illustrate the need to deconvolute the oat differential set using molecular tools.