Pleosporales » Lophiostomataceae

Platystomum

Platystomum Trevis., Bull. Soc. R. Bot. Belg. 16: 16 (1877).

Index Fungorum number: IF 4185; Facesoffungi number: FoF 00814, 40 morphological species (Species Fungorum 2022), 4 species with molecular data.

Saprobic on woody substrates in terrestrial habitats. Sexual morph: Ascomata solitary or gregarious, immersed to semi-immersed, papilla erumpent through host surface, coriaceous to carbonaceous, dark brown to black, globose to subglobose or conical, ostiolate. Ostiole slit or slot-like, central, papillate, with or without a crest, opening by an apical, lysigenous pore or dehiscence, usually plugged by gelatinous tissue, made up of lightly pigmented, pseudoparenchymatous cells. Peridium broad at the apex and thinner at the base, comprising two strata with several layers of brown or lightly pigmented to hyaline cells of textura angularis to textura prismatica, fusing and indistinguishable from the host tissues. Hamathecium comprising 1–3μm wide, numerous, branch or unbranched, septate, cellular pseudoparaphyses, situated between and above the asci, embedded in a gelatinous matrix. Asci 8-spored, bitunicate, fissitunicate, cylindric-clavate, pedicellate, apically rounded, with an ocular chamber. Ascospores uni to bi-seriate, partially overlapping, hyaline when immature, becoming brown to dark brown when mature, ellipsoidal to fusiform, muriform, 3–8 transversely septate, with 1–7 vertical septa, constricted at the central septum, lacking a mucilaginous sheath. Asexual morph: Coelomycetous. Conidiomata pycnidial, phoma-like, solitary, gregarious, dark brown to black, slightly erumpent, papillate, with a sphaerical mass of slimy conidia oozing out at ostiolar tip. Conidiomata wall multi-layered, with 3–4 outer layers of brown-walled cells of textura angularis, with inner most layer thin, hyaline. Conidiophores short, septate, sparsely branched, formed from the inner most layer of pycnidium wall. Conidiogenous cells phialidic, cylindrical, hyaline, flexuous, smooth, with short collarette. Conidia hyaline, aseptate, straight to curved, ellipsoidal, with rounded ends, thin-walled, smooth, numerous (adapted from Thambugala et al. 2015).

 Type species: Platystomum compressum (Pers.) Trevis.

Notes: Platystomum is characterised by pycnidial or avervular conidiomata, hyaline to pale brown, smooth, subglobose conidiogenous cells, and fusiform, ellipsoidal to obovoid conidia. Cesati and De Notaris (1863) referred Platystomum compressum previously known as Sphaeria compressa to Lophiostoma (Lophiostomataceae) based on immersed to erumpent ascomata with a cylindrical papilla. In the phylogenetic analysis of Mugambi and Huhndorf (2009), a putative strain of P. compressum grouped with Pseudotrichia guatopoensis and Xenolophium guianense and the authors suggested that this clade might correspond to the family Platystomaceae. Lumbsch and Huhndorf (2010) treated Platystomum in Pleosporales, genera incertae sedis. Hyde et al. (2013) and Wijayawardene et al. (2014) accepted Platystomum as a distinct genus in Platystomaceae. Thambugala et al. (2015) transferred Platystomum to Lophiostomataceae based on morphology and phylogenetic analysis. Platystomum resembles Lophiostoma but differs in having muriform ascospores, without a mucilaginous sheath or appendages (Thambugala et al. 2015). Thambugala et al. (2015) accepted Platystomum as a distinct genus in Lophiostomataceae based on a combined analysis of LSU, SSU, ITS and TEF1. Platystomum is morphologically and phylogenetically a distinct genus in Lophiostomataceae. Molecular markers available for Platystomum are ITS, LSU, SSU, RPB2 and TEF-1.

 

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