بیماری شانکر ناشی از Neopestalotiopsis clavispora روی گل رز در ایران

Rose (Rosa sp.) is a perennial flowering plant that belongs to the Rosaceae family. There are more than 200 species and more than 18,000 varieties of roses, and their cultivation is performed in both open fields and under greenhouse conditions. In sampling conducted in Isfahan province, diseased crowns and stems with symptoms such as canker and dieback were collected from Samurai and Tanja cultivars. Fungal isolates found from these samples caused sunken cankers with a yellow border on the stem of the rose. The clony of this fungus grew 65 to 70 mm in PDA culture medium at 25 °C and 12 h of darkness and 12 h of light. The aerial mycelia produced white colony with wavy surfaces and irregular margins. After 10 days, black acervuli with slimy spore masses formed on the surface of the petri dish. This isolate was observed in the back part of the Petri dish in the form of a yellow colony with black dots owing to the formation of acervules. Conidia were fusiform to clavate, straight or slightly curved, five-celled, and 4-septate, with a size of 6.3-8.2 x 18.4-27 µm. The basal cell in the condia is bright, elongated and conical with a hyaline appendage 5.8–6.8 µm long. The three median cells were versicoloured with darker walls than the rest of the cells. The second cell from the base was pale brown, the third cell darker brown, and the fourth cell darker. The apical cell was bright, short, and cylindrical to conical with 2-3 apical hyaline appendages of 19.2-29.5 µm. Conidiogenous cells were hyaline, short, simple, and cylindrical. To confirm morphological identification, after DNA extraction, ITS regions were amplified using polymerase chain reaction and sequenced. Based on the results obtained from the morphological characteristics and analysis of the ITS regions of the fungal isolates, Neopestalotiopsis clavispora was identified. To carry out pathogenicity, a suspension was prepared from seven-day-old progeny grown on PDA culture medium with a test of 106 spores per milliliter and inoculated into the stems of two-month-old Tanja digital rose plants. The fungal species were re-isolated from the necrotic symptoms, and Koch's postulates were confirmed. To our knowledge, this is the first report of canker disease and diedack caused by N. clavispora on roses in Iran.