Fungalpedia – Note 664, Microthyrium
Microthyrium Desm.
Citation when using this data: D. S. Marasinghe et al. 2023 (in prep.) – Fungalpedia, Ascomycota.
Index Fungorum, Facesoffungi, MycoBank, GenBank.
Classification: Microthyriaceae, Microthyriales, Dothideomycetidae, Dothideomycetes, Pezizomycotina, Ascomycota, Fungi
Epiphytic on the surface of leaves, twigs or stems appearing as tiny black spots. Superficial mycelium superficial, indistinct, composed of hyaline, branched, septate hyphae, sometimes with subcuticular haustoria. Sexual morph: Thyriothecia superficial, globose, ostiolate, solitary or gregarious, membranaceous or slightly carbonaceous, brown to light brown to, with a poorly developed basal layer, lenticular. Upper wall comprising cells of textura epidermoidea, radiating outwardly in parallel rows from the darker central ostiole. Peridium comprising a single stratum of cells, outer cells of small heavily pigmented cells of textura epidermoidea, inner cells light brown textura angularis. Hamathecium lacking or with hyaline, branched, septate, cellular pseudoparaphyses. Asci 8-spored, bitunicate, fissitunicate, narrowly obclavate to long fusiform, with small knob-like pedicel or pedicel lacking, ocular chamber not distinct, not staining blue in IKI. Ascospores overlapping 2–3-seriate, hyaline, fusiform to ellipsoidal, 1-septum, sometimes cilia present or absent, smooth-walled, guttulate or not. Asexual morph: Undetermined.
Notes: Microthyrium is the type genus of Microthyriaceae and was erected by Desmazieres (1841) with the type species M. microscopicum, which had been previously described by Arnaud (1918). However, the ciliate ascospores of M. macrosporum were first described by Müller and von Arx (1962). Since then, Bose and Müller (1964) and Ellis (1976) described ciliate taxa in the type species and other micro-thyriaceous fungi. Species of this genus are characterized by having flattened thyriothecia with cells of radially arranged and hyaline ascospores with cilia. Wu et al. (2011a) stated Leptothyrium as the asexual morph and we did not accept it until the sexual-asexual connection is confirmed with molecular data.
Type species: Microthyrium microscopicum Desm., Annls Sci. Nat., Bot., sér. 2 15: 138 (1841).
Other accepted species: Species Fungorum – search Microthyrium.
References
Arnaud G 1918 – Les Astérinées. Annales de l’école Nationale d’agriculture de Montpellier 16:1.
Bose SK, Muller E 1964 – Central Himalayan Fungi-1. Indian Phytopathol 17:3–22.
Ellis JP 1976 – British Microthyrium species and similar fungi. Trans Br Mycol Soc 67:381–394.
Müller E, von Arx JA 1962 –Beitr Kryptogamenfl Schweiz 11:1–922.
Entry by
Diana Sandamali Marasinghe, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai, 57100, Thailand School of Science, Mae Fah Luang University, Chiang Rai, 57100, Thailand, Mushroom Research Foundation, 128 M.3 Ban Pa Deng T. Pa Pae, A. Mae Taeng, Chiang Mai, 50150, Thailand
Published online 29 August 2023