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

Authors: NGUYEN, DUONG - Commonwealth Scientific And Industrial Research Organisation (CSIRO); HENNINGSEN, EVA - Commonwealth Scientific And Industrial Research Organisation (CSIRO); LEWIS, DAVID - Commonwealth Scientific And Industrial Research Organisation (CSIRO); MAGO, ROHIT - Commonwealth Scientific And Industrial Research Organisation (CSIRO); MCNEIL, MEREDITH - Commonwealth Scientific And Industrial Research Organisation (CSIRO); SUCHECKI, RADOSLAW - Commonwealth Scientific And Industrial Research Organisation (CSIRO); BODEN, SCOTT - University Of Adelaide; SPERSCHNEIDER, JANA - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Kianian, Shahryar; DODDS, PETER - Commonwealth Scientific And Industrial Research Organisation (CSIRO); FIGUEROA, MELANIA - Commonwealth Scientific And Industrial Research Organisation (CSIRO)

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2023
Publication Date: 12/19/2023
Citation: Nguyen, D.T., Henningsen, E.C., Lewis, D., Mago, R., McNeil, M., Suchecki, R., Boden, S., Sperschneider, J., Kianian, S., Dodds, P.N., Figueroa, M. 2023. Genotypic and resistance profile of two oat crown rust differential sets urge coordination and standardisation. Phytopathology. https://doi.org/10.1094/PHYTO-10-23-0353-R.
DOI: https://doi.org/10.1094/PHYTO-10-23-0353-R

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. At present, rust surveillance programs conducted by pathologists rely on race assignments (pathotype) to monitor rust evolution and movement and inform breeding programs and growers about which oat cultivars are suitable for seasonal planting. Races of rust fungi are commonly defined by a standard nomenclature system that links virulence phenotypes to race-specific genes postulated in subsets of crop lines, referred to as differential sets. In this study, we conducted a genotypic and phenotypic comparison of the widely utilised oat differential sets in Australia and the USA, which identified substantial discrepancies between lines supposed to represent the same differential in each set. This suggests the need for care to be taken in pathogen surveillance and postulation of R genes in breeding lines based on comparisons to the differential sets.

Technical Abstract: 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 of the cultivar Volta as the carrier of 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.