Pseudohelicomyces talbotii

Pseudohelicomyces talbotii (Goos) Y.Z. Lu & K.D. Hyde

≡ Helicosporium talbotii Goos, Mycologia 81(3): 368 (1989)

≡ Helicosporium ramosum Talbot, Bothalia 6:489–500. 1956

Index Fungorum number: IF 554891; Facesoffungi number: FoF 04747

Saprobic on decaying wood in a freshwater stream. Sexual morph: Undetermined. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, effuse, gregarious, white to pale brown. Mycelium composed of partly immersed, partly superficial, hyaline to pale brown, septate, branched hyphae, with masses of crowded, glistening conidia. Conidiophores macronematous, mononematous, cylindrical, mostly branched, septate, 25–260 μm long, 3.5–5 μm wide, subhyaline to brown, smooth-walled. Conidiogenous cells holoblastic, mono- to polyblastic, integrated, sympodial, terminal or intercalary, cylindrical, with denticles, 7–16 μm long, 3–5 μm wide, subhyaline to pale brown, smooth-walled. Conidia solitary, acropleurogenous, helicoid, rounded at tip, indistinctly multi-septate, 17–23 μm diam. and conidial filament 2–3 μm wide (x̄ = 20 × 2.5 μm, n = 20), 90–115 μm long, coiled 1½–2½ times, becoming loosely coiled in water, guttulate, hyaline to pale brown, smooth-walled. (Description from Luo 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 flat surface, edge undulate, reaching 21 mm in 3 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, Chiang Rai, Muang, Ban Nang Lae Nai, on submerged decaying wood in a freshwater stream, 25 March 2017, Yong-Zhong Lu, CR32 (MFLU 17–1106, reference specimen designated here; KAS 100776), living culture, MFLUCC 17–2021.

Notes: This taxon was initially described by Talbot (1956) as Helicosporium ramosum. Goos (1989) gave the name Helicosporium talbotii because H. ramosum was a later homonym of H. ramosum. Tsui et al. (2006) provided ITS and LSU sequence data for this taxon (H. talbotii MUCL 33010), but with no morphological descriptions. Zhao et al. (2007) described a new record of H. talbotii and provided its detailed descriptions and illustrations. Boonmee et al. (2014) mentioned that H. talbotii (MUCL 33010) clustered within Helicomyces in their phylogeny and they renamed it as Helicomyces talbotii but did not synonymize it (Boonmee et al. 2014). Other phylogenetic studies on the Tubeufiaceae also named Helicosporium talbotii (MUCL 33010) as Helicomyces talbotii (MUCL 33010) (Hyde et al. 2016; Brahamanage et al. 2017; Chaiwan et al. 2017; Lu et al. 2017, 2018; Luo et al. 2017; Phookamsak et al. 2018). However, there is still some taxonomic confusion as its valid name still remained as Helicosporium talbotii. In the present study, our multi-gene phylogenetic result shows that H. talbotii (MUCL 33010) clusters together with our new isolate MFLUCC 17–2021 within Pseudohelicomyces with high bootstrap support (Lu et al. 2018), and support that they should be the same species. We compared our new isolate to H. talbotii described by Talbot (1956), Goos (1989) and Zhao et al. (2007). They resemble each other in features of conidiophores, conidiogenous cells and conidia. We also compared the sequence data of MUCL 33010 with our new isolate MFLUCC 17–2021 and noted there is only one base pair difference and three missing gaps between MUCL 33010 and MFLUCC 17–2021 in their ITS sequence data and no difference in LSU (No protein gene data are available for MUCL 33010). Hence, we identify our new isolate and H. talbotii (MUCL 33010) as the same species and synonymize it under Pseudohelicomyces talbotii. As the sequenced collection of Pseudohelicomyces talbotii were not sequenced from the type specimen and were not detailed illustrated as well, we designated our new collection MFLU 17–1106 as a reference specimen.