Detection of oat crown rust disease in Taiwan (2019-2021)

Authors: HO, CHUNG-YING - National Taiwan University; HENNINGSEN, EVA - Commonwealth Scientific And Industrial Research Organisation (CSIRO); CHEN, SSU-TUNG - National Taiwan University; ARIYAWANSA, HIRAN - National Taiwan University; NAZARENO, ERIC - University Of Minnesota; SPERSCHNEIDER, JANA - Commonwealth Scientific And Industrial Research Organisation (CSIRO); DODDS, PETER - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Riddle, Jakob; Kianian, Shahryar; FIGUEROA, MELANIA - Commonwealth Scientific And Industrial Research Organisation (CSIRO)

Submitted to: bioRxiv
Publication Type: Rapid Release Publication
Publication Acceptance Date: 3/13/2024
Publication Date: N/A
Citation: N/A
DOI: https://doi.org/10.1101/2024.03.12.584714

Interpretive Summary: Oat crown rust is a devastating disease caused by Puccinia coronata f. sp. avenae. The pathogen has high evolutionary potential and can generate new virulences through mutations, meiotic recombination, and reassortment of virulence factors with the aid of its alternate host, common buckthorn (Rhamnus cathartica). Losses due to the disease could reach up to 50% in certain parts of the U.S.A rust-like disease outbreak was detected at the Experimental Farm of National Taiwan University in 2019, which caused significant damage to the field experiments. To determine the identity of the pathogen responsible for this disease outbreak, we collected infected foliar material. Disease signs suggested infection by the oat crown rust fungus. Hence, common procedures in rust pathology were applied to confirm the identity of the pathogen with phenotypic and molecular diagnostic techniques. A total of 50 field samples from infected oat cultivars were collected in 2019 and five rust isolates were purified in 2020 and 2021. Phylogenetic analysis based on ITS sequences indicated that the pathogen was likely Puccinia coronata f. sp. avenae (Pca), which was further supported by the placement of Taiwanese isolate NTU-01 with other Pca representatives in a phylogenetic tree of Basidiomycete fungi. Phenotyping assays across 36 oat differential lines demonstrated that Taiwanese isolates are phenotypically similar with relatively limited virulence. This study presents the first molecular confirmation of Pca in Taiwan and reports the virulence profiles of Taiwanese Pca population.

Technical Abstract: Oat is a minor forage crop grown in Taiwan. Only a few historical records of oat rust disease have been reported in the country, therefore the pathogen population remains poorly characterized. A rust-like disease outbreak was detected at the Experimental Farm of National Taiwan University in 2019, which caused significant damage to the field experiments. To determine the identity of the pathogen responsible for this disease outbreak, we collected infected foliar material. Disease signs suggested infection by the oat crown rust fungus. Hence, common procedures in rust pathology were applied to confirm the identity of the pathogen with phenotypic and molecular diagnostic techniques. A total of 50 field samples from infected oat cultivars were collected in 2019 and five rust isolates were purified in 2020 and 2021. Phylogenetic analysis based on ITS sequences indicated that the pathogen was likely Puccinia coronata f. sp. avenae (Pca), which was further supported by the placement of Taiwanese isolate NTU-01 with other Pca representatives in a phylogenetic tree of Basidiomycete fungi. Phenotyping assays across 36 oat differential lines demonstrated that Taiwanese isolates are phenotypically similar with relatively limited virulence. This study presents the first molecular confirmation of Pca in Taiwan and reports the virulence profiles of Taiwanese Pca population.