Dictyosporium tubulatum J. Yang, K.D. Hyde & Z.Y. Liu
Index Fungorum number: IF554771; Facesoffungi number: FoF04677
Etymology: Referring to the tubular conidial appendages.
Saprobic on decaying plant substrates. Sexual morph: Undetermined. Asexual morph: Colonies punctiform, sporodochial, scattered, dark brown to black, glistening. Mycelium mostly immersed, composed of smooth, septate, branched, hyaline to pale brown hyphae. Conidiophores micronematous, mononematous, septate, cylindrical, hyaline to pale brown, smooth-walled, 6.5–15 × 3.5–6 μm, sometimes reduced to conidiogenous cells. Conidiogenous cells monoblastic, integrated, terminal, determinate, hyaline to pale brown. Conidia acrogenous, solitary, cheiroid, smooth-walled, complanate, yellowish-brown to medium brown, mostly consisting of four arms closely compact with side arms lower than middle arms, rarely with five arms, 5–7-euseptate in each arm, guttulate, (22–)29–35(–38) × (14–)17–19(–22) μm (x̄ = 32.5 × 18 μm, n = 40), with hyaline, tubular, elongated appendages which are 19–24 × 3.5–7 μm and mostly attached at the apical part of two outer arms. (Descriptions from Yang et al. 2018)
Cultural characteristics: Conidia germinating on PDA within 24 h and germ tubes produced from the basal cell. Colonies on MEA reaching 5–10 mm diam. in a week at 25 °C, in natural light, circular, with fluffy, dense, white mycelium on the surface with entire margin; in reverse yellow in the middle and white at the margin.
Material examined: THAILAND. Prachuap Khiri Khan Province, near 12°30.19'N, 99°31.35'E, on decaying wood submerged in a freshwater stream, 25 December 2014, J. van Strien, Site 5-11-1 (MFLU 15-1166 holotype, HKAS 102136 isotype), ex-type living culture MFLUCC 15-0631; ibid. Trat Province, Amphoe Ko Chang, 12°08'N, 102°38'E, on decaying wood submerged in a freshwater stream, 27 April 2017, Y.Z. Lu, YJT 22-2 (MFLU 18–1044, HKAS 102137 paratype), living culture MFLUCC 17–2056.
Notes: Phylogenetic analyses showed that Dictyosporium tubulatum nested in Dictyosporium and sister to D. nigroapice. Dictyosporium tubulatum morphologically resembles D. alatum Emden, D. canisporum L. Cai & K.D. Hyde and D. thailandicum D’ souza, D.J. Bhat & K.D. Hyde in conidial ontogeny and conidial shape, colour and appendages. Dictyosporium tubulatum differs from the three species in the number of conidial cell rows. There are mostly four conidial columns in D. tubulatum while mostly five columns in the others. Dictyosporium tubulatum has smaller conidia (25–38 × 14–22 μm) than those in D. canisporum (32.5–47.5 × 20–25 μm) but has similar conidial size with D. alatum (26–32 × 15–24 μm) and D. thailandicum (15.4–34.5 × 14.5–20.6 μm) (Cai et al. 2003, Liu et al. 2015). Based on the molecular phylogeny, D. tubulatum is distinct from D. thailandicum and D. alatum. Unfortunately, molecular data are unavailable for D. canisporum. (Notes from Yang et al. 2018)
Freshwater distribution: Thailand (Yang et al. 2018)