Vaginatispora lignicola M.S. Calabon, E.B.G. Jones & K.D. Hyde, sp. nov.
Index Fungorum number: IF 559844; MycoBank number: MB 559844; Facesoffungi number: FoF 12721; Fig. 1
Etymology – Referring to this taxon dwelling on wood
Holotype – MFLU 22–0116
Saprobic on decaying wood submerged in freshwater habitats. Sexual morph: Ascomata 200–360×220–415 µm diam. (x̅= 269 × 294 µm; n = 10), scattered to gregarious, immersed to semi-immersed, erumpent at maturity, coriaceous, black, subglobose, ostiolate. Ostiole slot-like, central, elongated, pore-like opening, plugged by hyaline, filamentous hyphae, periphysate. Peridium 40–65 µm wide, circular, symmetric, outermost layer heavily pigmented, comprising a blackish to dark brown amorphous layer, flattened and loosely packed cells of textura angularis, inner layer composed of hyaline cell layers, flattened, thick-walled cells of textura angularis. Hamathecium 1.3–2.5 µm wide (x̅=1.9 µm, n=30) comprising numerous, filamentous, branched, septate, pseudoparaphyses. Asci 125–145 × 15–30 µm (x̅= 137 × 23 µm, n = 20), 8-spored, bitunicate, fissitunicate, cylindricalclavate, short-pedicellate, apex rounded with a minute ocular chamber. Ascospores 50–72 × 14–17 µm (x̅=62 × 16 µm, n=30), uniseriate to bi-seriate, overlapping, straight or slightly-curved, initially hyaline, becoming yellowish at maturity, fusiform, mostly with narrow acute ends, 1–3-septate, strongly constricted at the septa, smooth-walled, with numerous small guttules and 2 distinct large guttules. Asexual morph: Hyphae 2–5 μm wide, septate, hyaline to lightly pigmented, mostly smooth, thick-walled, moniliform. Chlamydospores 6–19×4.5–16 (x̅=10.9 × 8.4, n=50), numerous, mostly in short chains, globose to subglobose, smooth, initially hyaline then becoming light brown at maturity, arising from the mycelium, formed intercalarily or terminally.
Culture characteristics – Conidia germinating on malt extract agar (MEA) within 24 h. Germ tubes produced from the basal and apical cell of conidia. Colonies growing on MEA, reaching 20–25 mm in 2 weeks at 25 °C. Mycelia superficial, circular, with entire margin, flat, smooth, from above greyish brown to grey, from below dark grey to black.
Material examined – Thailand, Tak Province, Tha Sing Yang, Ban Mae Ja Wang on decaying wood submerged in a freshwater river, 17 October 2019, N. Padaruth, CC43 (MFLU 22–0116, holotype), ex-type living culture, MFLUCC 22–0078.
GenBank numbers – MW287233 ( L S U ) , MW287229(SSU), MW260329(ITS), MW512605(tef1), OP251197(rpb2)
Notes – Three species of Vaginatispora are recorded in freshwater habitats: V. aquatica (Hyde 1995; Tsui et al. 2000; Zhang et al. 2014a, b), V. armatispora (Hu et al. 2010; Bao et al. 2019; Hyde et al. 2019), and V. nypae (Hyde et al. 2020a, b, c; Boonmee et al. 2021). In this series, we introduce another novel species of Vaginatispora, V. lignicola, from a freshwater habitat in Thailand. Vaginatispora lignicola (MFLUCC 22–0078) confirms with the generic ascomatal morphology (erumpent, uniloculate, glabrous, slotlike ostiole, with numerous hyaline periphyses) but differs from the known members of the genus in having ascospores without a wide papilionaceous sheath or distinct hyaline appendages at both ends. Based on the phylogenetic analysis of combined LSU, SSU, ITS, tef1, and rpb2 sequence data, V. lignicola is basal to V. aquatica with high bootstrap support (97 ML and 1.00 BYPP) (Fig. 2). The former differs from V. aquatica in the measurement (50–72 ×14–17 µm vs 36–48 × 11–16) and color of the ascospores (initially hyaline then becoming yellowish at maturity vs hyaline), and the absence of a sheath when stained in Indian ink wherein the latter have wide papilionaceous sheaths (Hyde 1995). The novel taxon differs from the freshwater strains of V. armatispora and V. nypae by having larger ascospores (50–72×14–17 µm vs 22–30×5.5–8 µm vs 26–29×6–7 µm) without a mucilaginous sheath and hyaline appendages at both ends (Bao et al. 2019; Hyde et al. 2019; Boonmee et al. 2021). Multi-locus phylogenetic analyses showed that V. lignicola is a distinct taxon in Vaginatispora with 49 bp (9.32%, 526 bp) and 14 bp (1.74%, 804) nucleotide differences in the ITS and LSU sequence data of the type species, V. aquatica, respectively. The present work is the first report also of the morphological characteristics of the asexual morph of Vaginatispora. A simplified key to species of Vaginatispora is provided herein.
Figure 1 – Vaginatispora lignicola (MFLU 22–0116, holotype). a Host twig. b, c Appearance of erumpent ascomata in host substrate. d Vertical section of ascoma. e Slot-like ostiole with numerous periphysis. f Peridium. g Pseudoparaphyses. h Bitunicate asci. i Ocular chamber. j–n Ascospores in different stages of maturity. o Germinated ascospore. p Culture on MEA. q–s Hyphae. (t) Terminally and (u) intercalary swollen cells. v–x Moniliform hyphae with constricted septa. y–ab Multicellular bodies. Scale bars: a=2 mm, b–d=200 µm, e, g=20 µm, f=50 µm, h, j=100 µm, k–o, y, z=50 µm, q–x, aa=20 µm
Figure 2 – Phylogram generated from maximum likelihood analysis based on combined LSU, SSU, ITS, tef1, and rpb2 sequence data representing Lophiostomataceae (Pleosporales). Eighty-one strains are included in the combined analyses which comprised 3726 characters (741 characters for LSU, 973 characters for SSU, 526 characters for ITS, 1001 characters for tef1, and 1011 characters for rpb2) after alignment. Angustimassarina acerina (MFLUCC 14–0505) and Angustimassarina populi (MFLUCC 13–0034) in Amorosiaceae (Pleosporales) were used as the outgroup taxa. Bootstrap support values for ML≥75% are given above the nodes (left side) and BYPP≥0.95 are given above the nodes (right side). Ex-type strains are in bold and newly generated sequences are in blue