First report of Stemphylium vesicarium causing leaf blight of onion in Slovakia

During the 2022 growing season, commercial crops of onion ( Allium cepa cv. Medusa) were found to be affected by an extensive leaf blight in south western Slovakia. The pathogen present on diseased leaves was isolated and identified as Stemphylium vesicarium through morphological and molecular analyses, utilizing three DNA markers (ITS, tef1-α , and β-tubulin ). A detailed description and illustration of the fungus are provided. Although this pathogen is already present in Slovakia, this is the first record of S. vesicarium causing leaf blight on A. cepa in the country. Pathogenicity tests with a fungal isolate were performed on three local cultivars of onion plants in the laboratory, indicating varying susceptibility of the cultivars to S. vesicarium .