First report of Septoria silybi associated with leaf blotch of Silybum marianum from Iran

During March to April 2013, in the course of routine sample collection, a leaf spot disease was observed on Silybum marianum in different areas of Kermanshah province, Iran. Initial symptoms of the disease were pale brown, necrotic lesions, mostly 8-10 mm long on leaves. On the surface of the infected leaves conidiomata were observed, which were pycnidial, amphigenous, scattered, dark brown to blackish, globose, immersed in host tissue, becoming partly erumpent, unilocular, 90-150 µm in diameter, with an ostiole of 18-24 µm in diameter. Conidiogenesis was enteroblastic. Conidia were hyaline, filiform, sub-straight to mildly flexuous, truncate at the base, 20-48 × 1.2-2.8 µm, 2-5-septate, with indistinct septa. On the basis of symptoms, fungal morphology and completion of Koch’s postulate, the fungal isolates from the leaf spots were identified as Septoria silybi. This is the first report of S. silybi on leaves of S. marianum in Iran.