Xylariales » Xylariales, genus incertae sedis

Botryohypoxylon

Citation: Pem D et al. (2019) Mycosphere Notes 275-324: A morphotaxonomic revision and typification of obscure Dothideomycetes genera (incertae sedis). Mycosphere 10(1), 1115–1246

 

Botryohypoxylon Samuels & J.D. Rogers, Mycotaxon 25(2): 631 (1986)

Iledon Samuels & J.D. Rogers, Mycotaxon 25(2): 633 (1986)

Parasitic or lignicolous on trunks of dead tree. Sexual morph: Ascostromata rarely solitary, often cespitose in groups of 2–20 ascomata, ostiolate. Each ascoma arise on a cylindrical pedestal, globose with a tiny, acute papilla, only slightly wider than the pedestal, smooth, not collapsing when dry. Peridium with three discrete regions; outer region composed of cells of textura angularis, with long axes perpendicular to the surface of the ascomatal wall, individual cells with pigmented walls; middle region composed of cells of textura epidermoidea; inner region, the eel is fusoid, non- pigmented. Ascomatal apex composed of intertwined hyphae with lumens and pigmented with finger-like periphyses. Paraphyses forming a network between the asci, copious, branching, anastomosing, free ends not seen. Asci clavate, ascal cytoplasm abruptly narrowed below the ascospores at the point of dehiscence, dehiscing at the midpoint, forming a hymenium over the entire interior of the ascomatal wall, unitunicate with thin ectoascus and endoascus rather thick throughout the entire length of the ascus. Ascospores unicellular, hyaline when immature, dark brown, nearly opaque when mature, ellipsoidal. Asexual morph: Undetermined.

 

Type species – Botryohypoxylon amazonense Samuels & J.D. Rogers

 

Notes – Samuels & Rogers (1986) described the monotypic genus Botryohypoxylon with the type species B. amazonense, collected on trunks of dead trees in Amazonian Venezuela. Morphologically, this genus is distinct in its massive erumpent stroma which is accompanied by ‘eustromatic’ pycnidia with apparent phialides, unicellular ascospores, clavate, short-stipitate asci with a thin ectotunica and a thick endotunica, hamathecium consisting somewhat wide and branched pseudoparaphyses without free ends. The coelomycetous asexual state was observed in culture and described as Iledon. Botryohypoxylon is congeneric with Iledon (Index Fungorum 2019). Priority to the older sexual state was anticipated by Wijayawardene et al. (2014) and they proposed to use Botryohypoxylon over Iledon. The original author described Botryohypoxylon as unusual among bitunicate ascomycetes in having dark unicellular ascospores termed as an inconspicuous elongated germ-slit and has been found to have somewhat similar characteristics as Semidelitschia agasmatica (Cain & Luck-Allen 1969) and Loculohypoxylon grandineum (Berk & Rav.) Barr (Barr 1976). However, we re-examined the type specimen of Botryohypoxylon amazonense under the code NY02980804 and found that Botryohypoxylon has unitunicate rather than bitunicate asci. We therefore transfer the genus Botryohypoxylon to Xylariales, genera incertae sedis.

 

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