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

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.