Aposphaeria Sacc., Michelia 2(no. 6): 4 (1880).
Index Fungorum number: IF 7198; Facesoffungi number: FoF 00756, 84 morphological species (Species Fungorum 2022), 2 species with molecular data.
Saprobic in terrestrial habitats. Sexual morph: Saprobic on the dead twigs of Prunus padus L. Ascomata scattered or clustered in small to large groups, initially immersed, becoming erumpent to superficial, globose, black to dark brown, subcarbonaceous, ostiole central. Ostioles papillate, dark brown, smooth, periphyses filled ostioles cannel. Peridium composed of 9–13 layers of textura angularis, outer region haeavily pigment cells, black to dark-brown, inner layer composed of hyaline gelatinous cells, thin, merging with pseudoparaphyses. Hamathecium comprising numerous, long, broad, transversely septate, branched, trabeculate pseudoparaphyses. Asci (4)–8-spored, bitunicate, cylindrical, with club-shaped pedicel, apically rounded, with an ocular chamber up to 2–4 µm wide. Ascospores overlapping uniseriate, hyaline, broad-fusiform, conical at the apex, 1-transversely septate, strongly constricted at the septa, wall rough, not uniform, indentations present when mature (adapted from Tibpromma et al. 2017). Asexual morph: Conidiomata pycnidial, superficial, solitary, globose to subglobose, black, shiny, unilocular. Conidiomata wall thin, composed of one layer of medium brown, thick-walled cells of textura angularis. Ostiole single, circular, central, depressed. Conidiophores hyaline, branched at the base, septate above, short, cylindrical, and formed from the inner wall cells of the pycnidial wall. Conidiogenous cells enteroblastic, phialidic, integrated or discrete, determinate, hyaline, smooth, with apertures apical or lateral just below septa; collarette occasionally prominent, with minute channel, with thickened periclinal wall. Conidia hyaline, aseptate, thin-walled, eguttulate, cylindrical or ellipsoidal, smooth. Mycelium immersed, branched, septate, brown (adapted from Sutton 1980 and Tian et al. 2015).
Type species: Aposphaeria pulviscula (Sacc.) Sacc.
Notes: The type species Aposphaeria pulviscula previously known as Phoma pulviscula is poorly known. Boerema et al. (1996) re-studied the holotype of A. fusco-maculans and transferred it to Paraconiothyrium and this was followed by de Gruyter et al. (2012). de Gruyter et al. (2012) confirmed this placement based on molecular data. Some Aposphaeria or Aposphaeria-like taxa have also been reported in Massariosphaeria but these species are not confirmed with molecular data (Farr et al. 1989; Leuchtmann 1984; Kirk et al. 2001; Tanaka and Harada 2004). Wang et al. (2007) discussed the polyphyletic relationships of Aposphaeria, Massariosphaeria and Melanomma and suggested to include more asexual morph taxa to clarify this relationship. de Gruyter et al. (2012) showed that A. populina and A. corallinolutea are melanommataceous and several taxa in Aposphaeria are asexual morphs of Melanomma. In the phylogenetic analysis of Tian et al. (2015), Aposphaeria populina clustered with Melanomma pulvis-pyrius but A. corallinolutea formed a distinct clade hence the authors considered Aposphaeria and Melanomma as two distinct genera. Tibpromma et al. (2017) described the sexual morph of A. corallinolutea and suggested that Aposphaeria s. str. may not belong in Melanommataceae. Aposphaeria is morphologically and phylogenetically a distinct genus in Melanommataceae but more collections with sequence data are needed to confirm this taxonomic placement. Molecular markers available for Aposphaeria are ITS, LSU, SSU, RPB2 and TEF-1.
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