Neohelicosporium astrictum

Neohelicosporium astrictum Y.Z. Lu, J.C. Kang & K.D. Hyde

Index Fungorum number: IF 554869; Facesoffungi number: FoF 04737

Holotype: MFLU 17–1144

Etymology: “astrictum” referring to tightly helicoid conidia of this fungus.

Saprobic on decaying wood in a freshwater stream. Sexual morph: Undetermined. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, effuse, gregarious, white. Mycelium composed of partly immersed, partly superficial, hyaline to pale brown, septate, branched hyphae, with masses of crowded, glistening conidia. Conidiophores micronematous, mononematous, cylindrical, branched or unbranched, septate, 50–280 μm long, 3–4.5 μm wide, brown, smooth-walled. Conidiogenous cells holoblastic, mono- to polyblastic, integrated, sympodial, terminal or intercalary, cylindrical, with denticles, 11–20 μm long, 3.5–4.5 μm wide, brown, smooth-walled. Conidia solitary, acropleurogenous, helicoid, rounded at tip, 17–21 μm diam. and conidial filament 2–3.5 μm wide (x̄ = 19 × 2.8 μm, n = 50), 100–115 μm long, tightly coiled 2¼–2¾ times, not becoming loose in water, indistinctly multi-septate, guttulate, hyaline, smooth-walled. (Description from Lu et al. 2018)

Culture characteristics: Conidia germinating on water agar and germ tubes produced from conidia within 12 h. Colonies growing on PDA, circular, with umbonate surface, slightly wrinkle, edge entire, reaching 19 mm in 2 weeks at 28 °C, pale brown to brown in PDA medium. Mycelium superficial and partially immersed, branched, septate, hyaline to pale brown, smooth.

Material examined: THAILAND, Trat, Amphoe Ko Chang, Yuttha Navi Ko Chang Memorial, on submerged decaying wood in a freshwater stream, 27 April 2017, Yong-Zhong Lu, TW14 (MFLU 17–1144, holotype; HKAS 100815, isotype), ex-type living cultures, MFLUCC 17–2004, TBRC 8909.

Notes: Presently, there are three Neohelicosporium species, N. astrictum, N. aquaticum and N. ellipsoideum, in which the conidia do not become loosely coiled or uncoiled in water. Neohelicosporium astrictum is distinct from N. aquaticum by its smaller conidia diameter (17–21 μm vs. 27–32 μm) as well as the thinner and shorter conidial filaments (2–3.5 × 100–115 μm vs. 4–5.5 × 150–185 μm). Neohelicosporium astrictum is distinct from N. ellipsoideum by its thinner conidial filaments (2–3.5 μm vs. 5.5–7 μm) and thinner conidiophores (3–4.5 μm vs. 5–6 μm). Phylogenetically, N. astrictum constitutes an independent lineage with weak support and sister to N. fusisporum and N. parvisporum isolates within the genus Neohelicosporium. (Notes from Lu et al. 2018)

Freshwater distribution: Thailand (Lu et al. 2018)