Saprobic on dead stems or bark. Sexual morph: see Shang et al. (2019). Asexual morph: Conidiomata 1270–1600 µm diam., 450–520 µm high, brown, eustromatic, pycnidial, usually solitary, at maturity furfuraceous, immersed to erumpent, globose to subglobose in outline, conical in section view, multilocular, convoluted, thick-walled, glabrous, ostiolate. Ostiole 300–350 × 250–460 µm, single, circular, prominent, centrally located. Conidiomatal wall 30–200 µm wide, composed of dark brown, thick-walled cells of textura angularis to textura intricta in the basal and periclinal wall, gradually merging with brown or olivaceous cells of textura oblita in the middle wall, becoming rather thick-walled, dark brown cells of textura angularis at ostiolar region. Conidiophores formed from inner cells of the locular walls, hyaline, cylindrical, usually branched, septate, smooth-walled. Conidiogenous cells 7–14 × 1–3 µm, hyaline, enteroblastic, phialidic, cylindrical to subcylindrical, integrated or discrete, determinate, smooth-walled, with minute collarette near apex. Conidia 3–5 × 1–2 µm ( = 4.6 × 1.4 µm; n = 30), hyaline, allantoid, aseptate, smooth-walled, eguttulate.
Culture characters: Colonies on PDA, reaching 3–4 mm diam. after 14 d at 25–30°C, white at first, become dark brown with age, felty, flattened, dense, with undulate to lobate margin, reverse dark brown.
Material examined: Italy, Province of Forlì-Cesena, Premilcuore, Valbura, on dead land branches of Ostrya carpinifolia (Betulaceae), 1 March 2016, Erio Camporesi, IT2871 (MFLU 16-0940), living culture MFLUCC 16-1315 = ICMP 21537 = KUMCC 16-0085; ibid. Passo della Braccina, on dead land branches of Fagus sylvatica (Fagaceae), 10 August 2015, Erio Camporesi, IT2580 (KUN, HKAS 93600, new host record).
Notes: Two collections (MFLU 16-0940/IT2871, HKAS 93600/IT2580) clustered with C. prunicola (MFU 17-0995, MFLUCC 18-1200), C. gutnerae, and C. terebinthi (Fig. 107). The sequence of our collection HKAS 93600/IT2580 shares 100% similarity with C. prunicola (MFU 17-0995) in LSU (808/808), ITS (517/517), and rpb2 (778/778) regions. The sequence similarities between our strain (MFLUCC 16-1315) and C. prunicola (MFU 17-0995) are 99% (576/578, 2 gaps) in ITS, 99% (807/810, 22 gaps) in LSU, and 100% (778/778) in rpb2 region.Our collections have similar form of conidiomata, conidiogenous cells and conidia, as well as conidial dimensions with C. prunicola (Table 4). Therefore, our collections are considered conspecific with C. prunicola. Cytospora prunicola was described from Prunus sp. and Ostrya carpinifolia (Hyde et al. 2018, Shang et al. 2019). The collection (HKAS 93600/IT2580) from Fagus sylvatica is regarded as a new host record.
Cytospora prunicola (MFLU 16-0940) a Herbarium specimen. B–d Appearance of brown conidiomata on the host. E, f Vertical sections of conidiomata. G Ostiole. H–j Sections of peridium. K–m Conidiophores, conidiogenous cells and developing conidia. N Conidia. O Geminating conidium. P–q Culture on PDA. Scale bars b–c, f = 200 µm, d–e = 500 µm, g = 100 µm, h–I = 50 µm, j–k = 20 µm, l–o = 10 µm, p–q = 25 mm.