Biology subjects

Lewis, D. C.

Publications and source records attributed to Lewis, D. C..

3 recordsLinked to original sources

bioRxiv2024

Characterisation of virulence of Puccinia coronata f. sp. avenae in Australia in the 2023 growing season

Crown rust caused by the basidiomycete fungus Puccinia coronata f. sp. avenae (Pca) results in significant crop losses worldwide. Genetic solutions to protect against this disease require disease resistance gene discovery and introduction of resistance genes into elite germplasm by breeders. To inform disease resistance breeding activities, it is paramount to monitor changes of virulence in the Pca population and link those to genotypes of the pathogen. In 2023, a collection of 37 Pca isolates from diverse regions in Australia were gathered and their infection types across a commonly used set of oat differential lines determined to assign virulence pathotypes. We compared those virulence phenotypes to data collected in previous collections. While some of the virulence phenotypes had been reported in 2022, our analysis detected new virulence or an increase in frequency for virulence on some resistance genes. Notably, some of the frequency increases in virulence were recorded in Western Australia (WA), a region of interest due to its role in oat production for milling.

plant biology↗

bioRxiv2023

Genotypic and resistance profile analysis of two oat crown rust differential sets urge coordination and standardisation

Puccinia coronata f. sp. avenae (Pca) is the causal agent of the disease known as crown rust which represents a bottleneck in oat production worldwide. Characterisation of pathogen populations often involves race (pathotype) assignments using differential sets, which are not uniform across countries. This study compared virulence profiles of 25 Pca isolates from Australia using two host differential sets, one from Australia and one from the USA. These differential sets were also genotyped using DArT sequencing technology. Phenotypic and genotypic discrepancies were detected on eight out of 29 common lines between the two sets, indicating that pathogen race assignments based on those lines are not comparable. To further investigate molecular markers that could assist in the stacking of rust resistance genes important for Australia, four published Pc91-linked markers were validated across the differential sets and then screened across a collection of 150 oat cultivars. Drover, Aladdin, and Volta were identified as putative carriers of the Pc91 locus. This is the first report to confirm that the cultivar Volta carries Pc91 and demonstrates the value of implementing molecular markers to characterise materials in breeding pools of oat. Overall, our findings highlight the necessity of examining seed stocks using pedigree and molecular markers to ensure seed uniformity and bring robustness to surveillance methodologies.

plant biology↗

bioRxiv2023

Virulence patterns of oat crown rust in Australia - season 2022

Puccinia coronata f. sp. avenae (Pca) is an important foliar pathogen of oat which causes crown rust disease. 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 (WA). Several oat lines/Pc genes 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 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 substantially more broadly virulent than that of Australia. Close examination of resistance profiles for the oat differential set lines after infection with Pca supports hypotheses of allelism or redundancy among Pc genes 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.

plant biology↗