Characterization and report of Ectophoma multirostrata, causing stem canker disease in highbush blueberry in Iran

During a disease survey in greenhouses of blueberry seedlings in Mohammad Shahr City, Alborz Province, Iran, in the autumn 2021, severe stem canker symptoms were observed in the cv. Emerald of highbush blueberry (Vaccinium corymbosum). The disease incidence in the affected greenhouses was more than 30%–40%. Diseased branches and stems were sampled and the associated fungus was isolated on potato dextrose agar. Based on the fungal morphological features of the colony, three isolates among which the representative isolate of UT2020 were identified as Ectophoma multirostrata. Phylogenetic analysis of the concatenated ITS‐rDNA and beta‐tubulin (tub2) gene sequence data confirmed the morphological identification of the fungal isolates. E. multirostrata differs from closely related species by having several ostiolar necks, textura angularis wall in pycnidia and oblong to ellipsoidal conidia. The pathogenicity of the isolate UT2020 in the stems of highbush blueberry cv. Emerald was confirmed by our artificial wound inoculation method. After 14 days, the same stem canker symptoms were developed on the inoculated stems, and the same fungal isolate was re‐isolated from the newly developed symptoms, fulfilling the Koch's postulates. This is the first report of E. multirostrata causing a stem canker disease in highbush blueberries. Also, Vaccinium corymbosum is reported as a new host (matrix nova) for E. multirostrata worldwide.