Asterosporium asterospermum (Pers.) Hughes, Canad. J. Bot. 36: 738. (1958).
Basionym: Stilbospora asterosperma Pers. [as ‘asterospora’], Syn. meth. fung. (Göttingen) 1: 96. 1801.
Saprobic on twigs and branches of Fagus sylvatica L. Sexual morph: Undetermined. Asexual morph: Conidiomata 2–2.5 mm high, 0.8–1 mm diam. (x̅ = 2.1 × 0.86 mm, n = 15), acervular, subepidermal, erumpent at maturity, solitary, or occasionally confluent, unilocular, dark brown to black. Conidiomata wall 25–30 µm (x̅ = 29, n = 20), composed of thin-walled, brown cells of textura angularis. Conidiophores 30–35 µmhigh, 5–8 µm wide (x̅ = 29 × 7 µm, n = 20), cylindrical, branched at the base, septate, hyaline to pale brown. Conidiogenous cells 70–100 × 4–7 µm (x̅ = 80 × 5 µm, n = 20), holoblastic, cylindrical, unbranched, integrated, determinate, hyaline to pale brown, smooth-walled. Conidia 65–75 × 90–115 µm (x̅ = 68 × 100 µm, n = 20), terminal, transversely distoseptate, consisting of four arms, with reduced lumina, brown, smooth-walled (description based on Senanayake et al. 2017b).
Material examined: ITALY, Forlí-Cesena Province, Santa Sofia, near Passo la Calla, on dead branch of Fagus sylvatica L. (Fagaceae), 29 September 2012, E. Camporesi, MFLU 15–3555.
Notes: Asterosporium currently comprises five species as A. acerinum Wijayaw., Camporesi, McKenzie, K. Tanaka & K.D. Hyde, A. asterospermum (Pers.) S. Hughes, A. attenuatum Murvan. & Dekan., A. hoffmannii Kunze, and A. strobilorum Roum. & Fautrey (Index Fungorum 2018). The sexual morph of Asterosporium is undetermined (Tanaka et al. 2010). Auratiopycnidiellaceae Senan., Maharachch. & K.D. Hyde, in Senanayake et al. Stud. Mycol. 86: 217–296 (2017a).
Fig. Asterosporium asterospermum (MFLU 15–3555). a, b Conidiomata on host substrate. c Vertical section of conidiomata. d Conidiogeneous cells. e Conidia. Scale bars: a = 1 mm, b = 500 µm, c = 50 µm, d = 20 µm, e = 30 µm.