Pseudodactylaria albicolonia R.J. Xu, Boonmee & K.D. Hyde, sp. nov.
Index Fungorum number: IF 558548; MycoBank number: MB 558548; Facesoffungi number: FoF 09961; Fig. 1
Etymology – ‘albicolonia’ referring to the white colonies of this fungus.
Holotype – MFLU 21-0095
Saprobic on decaying submerged wood in a freshwater stream. Sexual morph Undetermined. Asexual morph Colonies effuse, gregarious, plentiful, white. Mycelium partly superficial, partly immersed in the substrate, consisting of branched, septate, smooth, hyaline hyphae. Conidiophores 43–85×3–5.5 μm (x̅=62×4 μm, n=11), macronematous, mononematous, unbranched, solitary, erect, subcylindrical, straight, or slightly flexuous, hyaline, sometimes light brown at the base 1–4-septate, smooth, sometimes expands at the base and slightly constricted at the septa of the apex. Conidiogenous cells 18–51×3–6 μm (x̅=34×4 μm, n=14), holoblastic, polyblastic, integrated, terminal, sympodial, subcylindrical, straight or flexuous, hyaline, rough-walled, apical part forming a rachis with numerous, denticles, sometimes percurrently regenerating. Conidia 14–19.5 × 2.5–4 μm (x̅=17×3 μm, n=30), acropleurogenous, solitary, fusiform, 0–1-septate, rarely slightly constricted at septum, hyaline, guttulate.
Culture characteristics – Conidia germinated on MEA media within 12 h and germ tubes were produced from both ends. Colony reached 3 cm at 28 °C in the dark for 1 week, on MEA media, circular, flat, with fluffy, dense, white mycelium, edge entire.
Material examined – THAILAND, Chiang Rai Province, Mueang, Ban Du, (99°49′18.12″ E 20°06′36″ N), on decaying submerged wood in a freshwater stream, 18 August 2020, R.J. Xu, MD-85 (MFLU 21-0095, holotype), ex-type culture, MFLUCC 21-0073.
GenBank number – ITS=MW751848, LSU=MZ493341.
Notes – Pseudodactylaria albicolonia shares several characters in common with P. fusiformis and P. camporesiana such as unbranched conidiophores, holoblastic, polyblastic conidiogenous cells and fusiform, hyaline conidia (Lin et al. 2018; Lu et al. 2020; Hyde et al. 2020b). Phylogenetically, P. albumcoloniam formed a distinct lineage basal to P. hyalotunicata and P. xanthorrhoeae with 86% MLBS, 1.00 BYPP support (Fig. 2). Pseudodactylaria albicolonia differs from P. hyalotunicata and the type species P. xanthorrhoeae in having shorter conidia (14–19.5×2.5–4 μm vs. 20–25×2.5–3 µm and (20–)22–27(–33)×(3–)3.5(–4) µm, respectively) and lacking a mucilaginous sheath (Tsui et al. 1997; Crous et al. 2017). Therefore, we introduce a new species P. albumcoloniam (Fig. 1) from a freshwater habitat in Thailand based on morphological differences and phylogenetic evidence.
Figure 1 – Pseudodactylariaalbicolonia (MFLU 21-0095, holotype). a Colony on decaying wood. b–d Conidiophores with conidia. e–g Conidiogenous cells with attached conidia. h–k conidia. l Colony on MEA medium. Scale bars: b–k=10 µm
Figure 2 – Phylogram generated from the best scoring of the RAxML tree based on combined LSU, ITS, sequence dataset to indicate the new species Pseudodactylaria albicolonia and related genera in Pseudodactylariales. Twenty-eight strains are included in the combined analysis, which comprise a total of 1306 characters. Arthrinium arundinis CBS 133509 and A. montagnei AFTOL ID-951 are selected as the outgroup taxa. The best RAxML tree with a final likelihood value of − 10010.943263 is presented. RAxML analysis yielded 664 distinct alignment patterns and 21.66% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.246125, C=0.236142, G=0.297752, T=0.219981, with substitution rates AC=0.978864, AG=2.183946, AT=1.688622, CG=0.686434, CT=5.976862, GT=1.000000; gamma distribution shape parameter alpha=0.403195. Bootstrap support values for maximum likelihood (MLBS, left) equal to or greater than 70% is given above the nodes. Bayesian posterior probabilities (BYPP, right) equal to or greater than 0.95 are given above the nodes. Newly generated sequences are in blue and bold