Blumeriella jaapii, a new fungal species on sour cherry in Guilan province, Iran

Sour cherry trees in Guilan Province are infected by at least two fungi that cause leaf spots and shot holes namely Wilsonomyces carpophilus and Pruniphilomyces circumscissus. In the late summer and early autumn of 2023, a leaf spot in the form of small purple-red to brown lesions about 1-3 mm in size was seen on the sour cherry trees in Sumaehsara County, Guilan Province, Iran. Mature conidiomata, acervuli, were formed frequently on the abaxial leaf surface at the center of each lesion, producing asexual conidia in white masses. Morphological and molecular studies showed that Blumeriella jaapii is associated with the sour cherry leaf spot disease. This is the first report on this fungus and the first attempt to sequence the ITS-nrDNA as the primary barcode of Blumeriella jaapii in Iran.