Virulence patterns of oat crown rust in Australia - season 2022

Authors: HENNINGSEN, EVA - Commonwealth Scientific And Industrial Research Organisation (CSIRO); LEWIS, DAVID - Commonwealth Scientific And Industrial Research Organisation (CSIRO); NGUYEN, DUONG - Commonwealth Scientific And Industrial Research Organisation (CSIRO); SPERSCHNEIDER, JANA - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Kianian, Shahryar; STONE, ERIC - Commonwealth Scientific And Industrial Research Organisation (CSIRO); DODDS, PETER - Commonwealth Scientific And Industrial Research Organisation (CSIRO); FIGUEROA, MELANIA - Commonwealth Scientific And Industrial Research Organisation (CSIRO)

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2024
Publication Date: 1/26/2024
Citation: Henningsen, E.C., Lewis, D., Nguyen, D.T., Sperschneider, J., Kianian, S., Stone, E., Dodds, P.N., Figueroa, M. 2024. Virulence patterns of oat crown rust in Australia - season 2022. Plant Disease. https://doi.org/10.1094/PDIS-09-23-1973-SC.
DOI: https://doi.org/10.1094/PDIS-09-23-1973-SC

Interpretive Summary: Puccinia coronata f. sp. avenae (Pca) is an important foliar pathogen that causes oat crown rust disease, which impacts oat production around the world. Sexual recombination, random (sequential) mutation and somatic hybridization are some of mechanisms allow rust pathogens such as Pca to alter their genetic make-up and gain virulence in otherwise resistant cultivars. The evolution of virulence in Pca is driven by an arms race between the pathogen and the host. The boom-and-bust cycle illustrates this process, as the pressure exerted by the extensive adoption of an oat cultivar with a disease resistance (R) gene leads to the selection of a rare variant in the pathogen that can overcome that specific resistant trait. This necessitates the need for continual monitor and survey of pathogen population to inform development of new resistant cultivars. In this work virulence profie of 48 Pca isolates derived from different location in Australia was characterized. Based on this analysis 42 unique races were detected among the 48 isolates, reflecting the high diversity of virulence phenotypes for Pca in Australia. These isolates were significantly less virulent than the US population indicating potential use of certain plant resistance genes in development of new cultivars for Australia.

Technical Abstract: Puccinia coronata f. sp. avenae (Pca) is an important foliar pathogen of oat which causes crown rust. The virulence profile of 48 Pca isolates 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 that Pca populations in Eastern Australia are broadly virulent, in contrast to the population in Western Australia. Several oat lines/Pc genes are effective against rust samples collected from WA, suggesting it may be worthwhile to stack with multiple genes to provide regional protection. We identified 19 oat differential lines from the US differential set that display disease resistance to Pca in 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 for Pca in Australia. Nevertheless, the Pca population in the USA is significantly more virulent than that of Australia. Close examination of resistance profiles for the oat differential set lines after infection with Pca supports hypothesis of allelism or redundancy among Pc genes or the presence of several R genes in a single oat differential line. These findings illustrate the need to deconvolute the oat differential set using molecular tools.