Morphological and molecular characterization of a novel Neopestalotiopsis clavispora, causing rose stem canker in Iran

Rose (Rosa spp.) is a widely cultivated perennial flowering plant grown in open fields and under controlled greenhouse conditions. This study focused on the isolation and characterization of a pathogen affecting Rosa hybrida plants in the Najafabad and Lenjan counties of Isfahan Province, Iran. Infected stems and crowns were collected from the greenhouses between July 2022 and September 2023. The cultivars affected were Samurai and Tanja. Fungal isolation was achieved, followed by morphological characterization and molecular identification by DNA sequencing of the internal transcribed spacer (ITS) regions, translation elongation factor 1-alpha (TEF1-α), and β-tubulin (TUB). Pathogenicity tests confirmed the ability of the isolate to induce stem canker and leaf spot symptoms in healthy Samurai and Tanja cultivars of rose (R. hybrida) plants, thereby fulfilling Koch’s postulates. The isolates were identified as Neopestalotiopsis clavispora by the morphological and molecular characteristics. To our knowledge, this study reports the first identification of N. clavispora as a pathogen causing canker disease and dieback on roses in Iran, emphasizing the need for effective management strategies to protect rose health and mitigate economic losses in the ornamental horticultural sector.