Apiosporaceae K.D. Hyde, J. Fröhl., Joanne E. Taylor & M.E. Barr, Sydowia 50(1): 23 (1998)
MycoBank number: MB 81935; Index Fungorum number: IF 81935; Facesoffungi number: FoF 00629; 114 species.
Saprobic or pathogenic on leaves, stems and roots of monocotyledons, mostly grasses, or endophytic on plant tissues, lichens, and marine algae, occasionally infecting humans, or isolated from soil. Sexual morph: Pseudostromata visible as raised, linear, blackened areas on the host surface, with neck and upper surface visible through splits in the host tissue, mostly gregarious, fusiform, ellipsoid to irregular, black cells between ascomata and darkened layer above usually thick, composed of brown cells of textura angularis. Ascomata solitary or usually gregarious in linear groups, immersed under pseudostromata, globose to subglobose, membranous, papillate, ostiole with periphyses. Peridium composed of several layers, comprising smallish, brown, reddish brown to hyaline cells of textura angularis. Paraphyses dense, hypha-like, long, broad, septate and branched. Asci 8-spored, unitunicate, broad cylindrical to clavate or subglobose, without an apical ring. Ascospores overlapping 1–3-seriate to irregularly arranged, hyaline, apiosporous, with a large, straight or curved, upper cell and smaller lower cell, usually surrounded by a gelatinous sheath. Asexual morph: Coelomycetous or hyphomycetous. Conidiomata sporodochial or acervuli, solitary to gregarious, immersed, erumpent from host tissue when mature, irregular, black, carbonaceous, coriaceous. Conidiomata wall composed of several layers of dark brown to hyaline cells of textura angularis, thick at the sides, thin at the upper and lower walls. Setae absent, or occasionally present, intermingled among conidiophores. Conidiophore mother cells ampulliform, verrucose wall, producing a single conidiophore. Conidiophores hyphoid, cylindrical, 1–2-septate, verrucose, flexuous. Conidiogenous cells basauxic, cylindrical, with or without verrucose wall. Conidia globose to subglobose, dark brown, smooth-walled or with minute wall ornamentations, with a truncate basal scar (adapted from Maharachchimbura et al. 2016b).
Type genus – Arthrinium Kunze
Notes – Apiosporaceae was introduced to accommodate taxa which produce apiospores and a basauxic, arthrinium-like conidiogenesis (Samuels et al. 1981, Hyde et al. 1998a, Bahl 2006, Senanayake et al. 2015, Dai et al. 2017, Wang et al. 2018, Pintos et al. 2019). Kirk et al. (2008), Senanayake et al. (2015), Maharachchikumbura et al. (2016b) and Wijayawardene et al. (2018a) accepted six genera viz. Appendicospora, Arthrinium (= Apiospora), Dictyoarthrinium, Endocalyx, Scyphospora and Spegazzinia in this family.
Appendicospora was placed in this family based on its apiospores, and it differs from Arthrinium in having ascospores with a bifurcate appendage at the lower cell (Hyde 1995b). This genus includes two species, A. coryphae, and A. hongkongensis, however, only A. hongkongensis and an unidentified species with sequence data. A blast search of SSU sequences in GenBank shows Appendicospora is similar to Arthrinium, however, it is more similar to Oxydothis based on the LSU rDNA sequences. Phylogenetic analyses of Appendicospora are required to clarify its relationship within Apiosporaceae. Dictyoarthrinium is a hyphomycetous genus with basauxic conidiophores and conidiogenous cells producing 4-celled, cruciately septate conidia. Endocalyx was established in Apiosporaceae on the basis of its basauxic conidiophores, however, species of Endocalyx usually produce funnel-shaped to elongated cupulate sporodochia, which are not observed in other genera of this family (Seifert et al. 2011). Spegazzinia produces basauxic conidiophores and conidiogenous cells with a basal mother cell and stellate to disc-shaped conidia with radiating spine-like appendages (Seifert et al. 2011). Tanaka et al. (2015) transferred Spegazzinia to Didymosphaeriaceae based on the establishment of two species phylogenetically assigned in this family. Two more species were included in Didymosphaeriaceae based on morphology and phylogenetic analysis (Thambugala et al. 2017, Jayasiri et al. 2019), thus, this genus is no longer included in Apiosporaceae. Scyphospora was introduced by Kantschaveli (1928) and typified by S. phyllostachydis. Index Fungorum (2020), however, synonymized the type species under Arthrinium hysterinum, probably based on morphology. The hand drawings of both epithets provided by Nag Raj (1974) and Kirk (1986) also show they are the same species. Therefore, we accept the combination as in Index Fungorum (2020) and regard Scyphospora as a synonym of Arthrinium. Nigrospora was introduced by Zimmermann (1902) and redrawn by Seifert et al. (2011). Wang et al. (2017) transferred Nigrospora to Apiosporaceae based on morphology and phylogeny. Thus, we conclude that Apiosporaceae accommodates five genera. We illustrate a new species, Arthrinium neogarethjonesii with sexual and asexual morphs.