Trichomerium Speg., Physis, Rev. Soc. Arg. Cienc. Nat. 4(no. 17): 284 (1918)

MycoBank number: MB 5560; Index Fungorum number: IF 5560; Facesoffungi number: FoF 10395; 29 morphological species (Species Fungorum 2021), 7 species with molecular data.

Epiphytic on the upper surface of leaves. Hyphae, branched, septate, slightly constricted at the septa, pale brown to dark brown, hyphal networks cover the surface of hosts. Sexual morph: Ascomata superficial, solitary to aggregated, subglobose to globose, brown to dark brown, sometimes setose. Setae brown to dark brown or olivaceous, erect, straight or curved, septate or continuous. Peridium two layers, the outer layer of brown to dark brown cells of textura prismatica, the inner layer composed of pale brown to hyaline of flattened cells. Hamathecium lacking. Asci 8-spored, bitunicate, ellipsoidal to cylindrical, clavate, with a short pedicel, with an apical ring. Ascospores overlapping 2-seriate, hyaline, fusoid, rounded at the ends, 2−3-septate, guttulate, with or without a mucilaginous sheath. Asexual morph: hyphomycetous. Conidiophores reduced to conidiogenous cells, conidia arising directly from hyphae. Conidia solitary, hyaline to pale brown, or grayish, giving rise to 3−4 lateral arms from a central cell. Conidial arms subcylindrical, tapering to the apex, with rounded ends, pale brown to grayish, 2−5-septate, not constricted or slightly constricted, darker at the septa, smooth-walled (Hongsanan et al. 2016).

Type species: Trichomerium coffeicola (Puttemans) Speg.

Notes: Trichomerium was introduced by Spegazzini (1918), with its type species T. coffeicola. However, because of lacking holotype specimen of T. coffeicola and also no molecular data available, Chomnunti et al. (2012) proposed T. foliicola as the type species of Trichomerium. The foliar epiphyte genus Trichomerium occurs superficially on living leaves of a variety of plants (Chomnunti et al. 2012b, Hongsanan et al. 2016, Maharachchikumbura et al. 2018). Trichomerium have been poorly studied, it is estimated that the genus includes 29 species (Species Fungorum 2021), however, only seven species have sequence data. Crous et al. (2015) confirmed introduced a new species Trichomerium dioscoreae with Tripospermum-like morphs. Subsequently, Hongsanan et al. (2016) introduce the asexual morph of Trichomerium gloeosporum with Tripospermum-like morphs and confirmed based on phylogenetic analysis.