Dematiohelicoma
Dematiohelicoma Y.Z. Lu, J.C. Kang & K.D. Hyde, in Lu et al., Fungal Diversity 92: 157 (2018).
Index Fungorum number: IF 554821; Facesoffungi number: FoF 04700, 2 morphological species (Species Fungorum 2022), 2 species with molecular data.
Saprobic on decaying wood. Sexual morph: Unknown. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, effuse, gregarious, hairy, black. Mycelium mostly immersed, partly superficial, composed of branched, septate hyphae, brown to dark brown. Conidiophores macronematous, mononematous, erect, cylindrical, unbranched, septate, arising as lateral branches from creeping hyphae, pale brown to brown, smooth-walled. Conidiogenous cells holoblastic, mono- to polyblastic, sympodial, integrated, terminal and intercalary, cylindrical, truncate at apex after conidial secession, pale brown to brown, smooth-walled. Conidia acropleurogenous, helicoid, solitary, rounded at apex, tapering gradually towards truncate basal cell, basal cells hyaline or subhyaline, multiseptate, dark brown septa, tightly coiled 2–3 times, not becoming loose in water, brown to dark brown, smooth-walled (adapted from Lu et al. 2018).
Type species: Dematiohelicoma pulchrum (R.F. Castañeda & Guarro) Y.Z. Lu & K.D. Hyde
Notes: Dematiohelicoma is characterised by immersed, partly superficial brown to dark brown mycelium, holoblastic, mono- to polyblastic conidiogenous cells, acropleurogenous, helicoid, solitary, multiseptate conidia. Dematiohelicoma pulchrum previously known as Helicoma pulchrum is morphologically similar to H. perelegans but differs from other helicosporous species in conidial characteristics (Zhao et al. 2007, Lu et al. 2018). Helicoma pulchrum and H. perelegans have conidia with hyaline or subhyaline basal cells, tapering gradually towards a truncated base with the remaining cells being reddish-brown and conidial septa are dark brown and darker than the adjacent parts. These morphological characters are not congeneric with the concept of Helicoma and other helicosporous genera and hence was accommodated in a separate genus Dematiohelicoma. Helicoma pulchrum was transferred to Dematiohelicoma pulchrum and chosen as the type species. Helicoma perelegans was synonymized under Dematiohelicoma perelegans (Lu et al. 2018). ITS, LSU and SSU sequence data are available for Helicoma pulchrum while only ITS data is available for Helicoma perelegans. More taxa of Dematiohelicoma are needed to confirm the status of the genus within Tubeufiaceae.
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