First report of Stemphylium eturmiunum causing leaf blight of garlic (Allium sativum L.) in Iran

Garlic leaf blight caused by Stemphylium eturmiunum was detected in Iran, representing a potential threat locally. During field surveys and disease monitoring conducted over three consecutive growing seasons (from 2018 to 2021) in major garlic growing areas of Tarom County, Zanjan Province, Iran, severe leaf blight, yellowing and desiccation were frequently observed, with disease incidence around 65–85%. In total, 500 symptomatic samples were collected from 100 inspected fields, yielding 167 fungal isolates, of which 43 were identified as Stemphylium -like based on morphological characteristics. Based on morphological characteristics together with multilocus phylogenetic analyses for six selected isolates using ITS region, GAPDH , and cmdA gene sequences, isolates were identified as Stemphylium eturmiunum . Phylogenetic analyses placed the Iranian isolates within a well-supported clade (100/0.99) of S. eturmiunum , including the ex-type culture CBS 109845. Pathogenicity tests under greenhouse conditions initially produced small leaf spots that subsequently expanded into blight lesions on inoculated garlic seedlings. The pathogen was re-isolated from symptomatic plants, and the morphology of the re-isolated cultures was consistent with the original isolates, thereby fulfilling Koch's postulates. To the best of our knowledge, this study represents the first report of Stemphylium eturmiunum causing garlic leaf blight in Iran. Although the current data provide initial insight into the presence of this pathogen, further research is required to clarify its epidemiology and to establish effective control measures.