Saprobic on dead twigs of Platanus orientalis. Sexual morph: undetermined. Asexual morph: Conidiomata 720–850 µm diam., 400–520 µm high, brown, pycnidial, usually solitary, deeply immersed at first, becoming erumpent, furfuraceous at maturity, subglobose in section view, multilocular, convoluted, thick-walled, glabrous, ostiolate. Ostiole 350–400 × 200–300 µm, single, circular, prominent, centrally located. Conidiomatal wall 20–140 µm wide, composed of brown, thick-walled cells of textura angularis to textura intricta. Conidiophores arising from inner wall layer of locules, hyaline, cylindrical, branched at base and above, septate, smooth-walled. Conidiogenous cells 5–12 × 1–2 µm, hyaline, enteroblastic, phialidic, cylindrical to doliiform, integrated or discrete, determinate, with a short terminal or lateral branch formed immediately below a septum, thickening at collarette zone. Conidia 4–8 × 1–2 µm ( = 6 × 1.5 µm; n = 50), hyaline, cylindrical or allantoid, with obtuse ends, straight or curved, unicellular, smooth-walled, eguttulate.
Material examined: Germany, on dead twigs of Platanus orientalis (Platanaceae), 3 March 2013, René K. Schumacher, D5 (MFLU 19-2857).
Notes: The conidiomatal structure of our collection is close to C. ulmi (Norphanphoun et al. 2017). However, our collection has cylindrical to doliiform, acropleurogenous conidiogenous cells, a feature lacking in C. ulmi. As our collection lacks protein gene (e.g., rpb2), and it cannot be separated well from other Cytospora taxa, we keep it as an unidentified taxon. Fresh collections of this taxon are needed to clarify its placement.
Cytospora sp. (MFLU 19-2857) a Herbarium specimen. b, c Appearance of brown coniodiomata on the host. d, e Vertical sections of conidiomata. f Ostiole. g, h Sections of peridium. i–k Conidiophores, conidiogenous cells and developing conidia. l Conidia. Scale bars c = 500 µm, d–e = 200 µm, f = 100 µm, g–h = 50 µm, i–l = 10 µm.
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