Helicoma aquaticum Y.Z. Lu, J.C. Kang & K.D. Hyde, in Lu et al. Fungal Diversity 92: 174 (2018).
Index Fungorum: IF 554836; MycoBank number: MB 554836; Facesoffungi number: FoF04712; Fig. 1
Saprobic on decaying fruits of Dipterocapus sp. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, gregarious, brown. Mycelium composed of partly immersed, partly superficial, hyaline to pale brown, septate, hyphae. Conidiophores macronematous, mononematous, cylindrical, erect, straight, unbranched, septate, 119–180 μm long, 6.5–7 μm wide, the lower part brown to dark brown, the upper part pale brown, smooth-walled. Conidiogenous cells holoblastic, mono- to polyblastic, integrated, intercalary, cylindrical, with denticles, arising laterally from the lower part of conidiophores, 10–15 × 5–9 μm (x̅=12 × 7 μm, n=20), brown, smooth-walled. Conidia solitary, pleurogenous, helicoid, tapering towards apex, rounded at tip, 33–37 μm diam. and conidial filament 3.5–6 μm wide (x̅=5 μm, n=20), 290–376 μm long (x̅=321 μm, n=20), 20–27-septate, constricted at septa, coiled 11 /2–41 /4 times, becoming loosely coiled or uncoiled in water sometimes, hyaline to pale brown, smooth-walled. Sexual morph: Not observed.
Culture characteristics – Colonies growing on PDA at 25 °C, edge undulate, flat, circular, spreading, with fluffy pale brown air-mycelium, pale brown to brown mycelium. reverse dark brown, pale brown at the edge side, lobate at the center, without pigmented.
Material examined – Thailand, Chiang Mai Province, MRC, on dead fruits of Dipterocarpus sp. (Dipterocarpaceae), 15 August 2019, Xia Tang, Dip 18 (MFLU 21-0176), living culture MFLUCC 21-0141.
GenBank numbers – OM232106 (ITS), OM248446 (LSU), OM272846 (tef1)
Hosts – Unindentified submerged decaying wood (Lu et al. 2018), dead fruits of Dipterocarpus sp. (Dipterocarpaceae) (this study).
Distribution – Thailand (Lu et al. 2018, this study).
Notes – Helicoma aquaticum was described and illustrated by Lu et al. (2018) from an unidentified submerged decaying wood in Thailand. Based on the morphological characteristics, our collection shares similar morphology with the ex-type strain (Fig. 2). Comparisons of ITS, LSU and tef1 sequence data between our collection and the holotype showed that they are 2/ 549 bp (0.3%) of ITS, 9/1201 (0.7%) of LSU and 9/879 bp (1%) of tef1. We consider that our collection is the same as Helicoma aquaticum following the guidelines for species delineation proposed by Jeewon and Hyde (2016). This is the first report of Helicoma aquaticum on a Dipterocarpus sp. in Thailand.
Figure 1 – Helicoma aquaticum (MFLU 21–0176, new host record) a, b Host. c, d Conidiophores. e Conidiophore with conidiogenous cells. f–h Conidia. i Germinated conidium. Scale bars: b=100 μm, c–e=50 μm, f–h=10 μm
Figure 2 – Phylogram generated from parsimony analysis based on combined ITS, LSU and tef1 sequence data of Helicoma. ML and MP bootstrap support values ≥ 70% are indicated above the nodes, and branches with Bayesian posterior probabilities ≥ 0.95 are given above the nodes. The ex-types (reference strains) are in bold; the new isolates are in blue bold. The tree is rooted with Kamalomyces thailandicus (MFLUCC 13–0233) and Kamalomyces thailandicus (MFLUCC 11–0158)