Helicosporium Nees, Syst. Pilze (Würzburg): 68 (1816) [1816-17].

Helicotrichum Nees & T. Nees, Nova Acta Acad. Caes. Leop.-Carol. 9: 246 (1818)

?Drepanospora Berk. & M.A. Curtis [as ‘Drepanispora’], in Berkeley, Grevillea 3(no. 27): 105 (1875)

Saprobic on leaves, bark, and twigs, oron stromata of Diatrype stigma, Diatrypaceae (Xylariales), on decorticated or decaying wood, in terrestrial habitats or submerged in freshwater, widespread in temperate to tropical regions. Sexual state:Ascomatasuperficial, solitary, scattered, globose-subglobose, bright yellow brown to yellow orange, collapsing when dry, darkened near ostiole. Peridium ofseveral layers, composed of bright yellow cells of textura prismatica to angularis. Hamathecium comprising numerous, filiform, septate, branched, hyaline pseudoparaphyses. Asci 8-spored, bitunicate, cylindric-clavate, apedicellate, thickened at apex, with an acute ocular chamber. Ascospores biseriate, elongate-fusiform, tapering towards narrowly subacute ends, trans-septate, hyaline. Asexual state: hyphomycetous, helicosporous.Conidiophoresmacronematous, mononematous, setiferous, erect, septate, unbranched, dark brown, fertile in middle, sterile,tapering towards narrow subacute at apex, smooth-walled,arising directly on substrate, from thick-walled, closely septate, recumbent hyphae, crowded or in fascicles, glistening, light coloured. Conidiogenous cells polyblastic, intercalary, rarely terminal, with lateral minute denticles each with single conidium. Conidia coiled 3½–4½ times, tightly to loosely coiled, rounded at apical end, truncate at base, hyaline, 7–13-septate, slightly constricted at septa, smooth-walled.

Type species: Helicosporium vegetum Nees

Notes: Helicosporium was introduced by Nees (1817) based on H. vegetum. At present Helicosporium species are polyphyletic within the family Tubeufiaceae and are related with sexual states in the genera Acanthostigma, Acanthostigmina and Tubeufia (Tsui and Berbee 2006; Tsui et al. 2006, Fig. 2). In our analysis, the type species of Helicosporium, H. vegetum is linked with Tubeufia cerea (Berk. & M.A. Curtis) Höhn.(Clade D, Fig. 2) with highsupport (99% BS and 1.00 PP) and thus synonymized. InHelicosporiumascomata are bright yellow brown to yellow orange and formed on stromata of other fungi, and ascosporesare elongate-fusiform, tapering towards narrowly subacute ends, trans-septate, hyaline, withhyaline, helicoid conidia and borne directly on small denticles on setiferous conidiophores which are terminally sterile.The ex-type cultures of Helicoma vaccinii (CBS 216.90) and Acanthostigma patagonica (MVB 573 BBB) cluster in Clade D (Fig. 2) with strains of Helicosporiumsensu stricto. Helicoma vaccinii produces terminal conidia (Carris 1989) while no asexual state is known for Acanthostigma patagonica (Sánchez et al. 2012).