Pseudophialocephala humicola (S.C. Jong & E.E. Davis) M.S. Calabon, E.B.G. Jones, K.D. Hyde, comb. nov.
MycoBank number: MB 559312; Index Fungorum number: IF 559312; Facesoffungi number: FoF 10604;
= Phialocephala humicola S.C. Jong & E.E. Davis, Mycologia 64(6): 1352 (1973) [1972]
Saprobic on submerged decaying culms from salt marsh habitats. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Colonies on natural substate effuse, white, velvety. Mycelium mostly immersed, composed of hyaline, branched, septate and constricted at the septa, guttulate hyphae, 1.5–3 μm wide. Conidiophore determinate, macronematous, composed of stipe and penicillate heads. Stipe 350–700 μm long, 4.5–9.0 μm wide at base, 2.5–6.0 μm wide at tip, mononematous, 9–12 septate, 0.2–0.6 um thick wall, erect, straight, or broadly curved, cylindrical, brown, and wide at base, paler and slightly tapering toward the apex, terminated by a penicillate head. Penicillate heads composed of 1–2 series of metulae terminating in groups of conidiogenous cells. Metulae thin-walled, light brown to subhyaline, primary metulae 6–12 × 1.8–3.3 (x̄ = 8.9 × 2.5) um, secondary metulae 4.5–6.5 × 1.5–4.0 (x̄ = 5.5 × 2.7) um. Conidiogenous cells 5.6–10.2 × 1.4–4.5 (7.7 × 3.0) um monophialidic, discrete, determinate, terminal, clustered at the apex of secondary metulae, hyaline, thin-walled, cylindrical, with inconspicuous openings, with minute collarettes. Conidia 1.8–3.8 × 1.4–2.4 (x̄ = 3.0 × 1.8) um, acrogenous, aseptate, aggregated in slimy and white masses, solitary to catenate, hyaline, ellipsoidal, rounded at each end, smooth, thin-walled, 1–2 guttules.
Culture characteristics – Conidia germinated on saltwater MEA within 24 h. Germ tubes arising from different ends of the conidia. Colonies growing on MEA, reaching 30–40 mm in 4 weeks at 25 °C. Mycelia superficial, circular, with entire margin, flat, smooth, obverse grayish brown to brown, from below dark brown.
Material examined – THAILAND, Prachuap Khiri Khan, Pran Buri, on submerged decaying leaf blades of Spartina sp., 9 September 2020, M.S. Calabon, SS223 (MFLU 21–**), living culture (MFLUCC 21–**).
GenBank numbers – LSU: **, ITS: **
Distribution: USA, soil (Jong and Davis 1972), JAPAN, decaying tree, paddy field soil (Kiyuna et al. 2012), CHINA, soil (Chunyu et al. 2013), THAILAND, submerged decaying Spartina culm (this study).
Notes – Pseudophialocephala humicola was isolated from soil in USA (Jong and Davis 1972) and this species was subsequently isolated from the same substrate in other studies in Australia (Matsushima 1989), China (Matsushima 1980), Japan (Matsushima 1975), and USA (Ellis 1976), and recorded from different plant hosts from China (Matsushima 1980) and Japan (Matsushima 1975). The BLASTn search result of ITS sequence data of Pseudophialocephala humicola MFLUCC 21-** had 71 hits in Sordariomycetes with 100% identity in different strains of P. humicola (32E, NBRC 31686, CBS 420.73, CBS 601.66). LSU BLASTn resulted to 99 hits of Sordariomycetidae with 100% and 99.75% similarities with P. humicola (CBS 601.66) and Chloridium salinicola (MFLU 19-1238), respectively. The preliminary single gene phylogenetic analysis of the top 100 BLASTn hits resulted in a well-defined close association of P. humicola to Chaetosphaeriaceae taxa. The combined ITS-LSU phylogenetic analyses revealed that MFLUCC 21-** clustered with the holotype, P. humicola CBS 420.73, and other strains (CBS 601.66, NBRC 100578) (Figure 33). Morphological comparison of P. humicola MFLUCC 21-** shows similarity with the description of the holotype except for the presence of the tertiary metulae that was observed from the holotype. The comparison of the ITS and LSU sequence data of MFLUCC 21-** showed no base pair differences with CBS 420.73 and CBS 601.66, respectively. Based on morphology and phylogenetic analysis, this confirms the new host record in Spartina sp., new geographical record in Thailand, and new report of Pseudophialocephala humicola in marine habitats, and second report of the genus thriving in the marine ecosystems.
Figure 36 – Pseudophialocephala humicola (MFLU–**) a Appearance of conidiophore and conidia on natural substrate. b–d Conidiophores, conidiogenous cells, and conidia. e–h Conidiogenous cells and conidia. i Conidia. Scale bars: a = 200 µm, b–d = 100 µm, e–h, i = 20, h = 5 µm.