Hypoxylon zhaotongensis G.Q. Zhang & D.Q. Dai, 2023

Zhang, Gui-Qing, Dai, Dong-Qin, Wijayawardene, Nalin N., Promputtha, Itthayakorn, Bhat, D. Jayarama, Dawoud, Turki M., Tibpromma, Saowaluck & Wei, Xiao-Mei, 2023, Taxonomy and phylogeny of Hypoxylon zhaotongensis sp. nov. (Hypoxylaceae, Xylariales), a bambusicolous fungus from Yunnan, China, Phytotaxa 598 (2), pp. 111-123 : 118-119

Hypoxylon zhaotongensis G.Q. Zhang & D.Q. Dai sp. nov. ( FIGURE 2 )

Index Fungorum number: IF900387; Facesoffungi number: FoF 14108

Holotype: GMB 1373

Etymology: Named after the location “Zhaotong” where the new taxon was first discovered.

Saprobic on decaying bamboo culms. Sexual morph: Stromata 1–10 cm long × 0.5–1 cm broad, pulvinate, with conspicuous perithecial mounds, gregarious, initially buried, later forming a black (000000) dome-shaped and purple (800080) to brown brick (a52a2a) multi-layered perithecial mound. Perithecia 0.1–0.5 mm diam. × 0.2–0.6 mm high, globose to subglobose, dark brown (654321), with an opened ostiole, yielding yellowish-brown (996515) pigments in 10% KOH. Ostioles papillate, 50–60 μm broad × 50–65 μm high. Peridium comprises multiple layers of cells of textura angularis, 15–30 μm thick, with thin-walled cells forming a colorless inner layer, with thick-walled cells forming the dark brown (654321) outer layer. Hamathecium comprising 2–3 µm wide, numerous, septate, branched, filamentous paraphyses. Asci 70–125 × 6–12 µm (x = 90 × 5 μm, n = 20), 8-spored, unitunicate, cylindrical or clavate, hyaline, pedicellate, with a “J+” sub apical apparatus, 0.4–0.6 µm high × 3.0–3.5 µm broad, faintly bluing in Melzer’s reagent, with 10–35 µm long basal stipes. Ascospores 10–20 × 7–9 μm (x = 15 × 8 μm, n = 20), ellipsoidal, uniseriate to overlapped, narrow at both ends, smooth at surface, initially hyaline to pale brown (987654) when immature, dark brown (654321) at maturity, 1–4 guttulate, with conspicuously straight germ slit less than spore-length on the convex side, aseptate. Asexual morph: Undetermined.

Culture characters: Ascospores germinating on PDA within 24 h and germ tubes produced from both sides. Colonies slow-growing, 4.5–8 mm diam. after 30 days at 28 °C, under normal light; from above circular, with even and white (ffffff) margin, brown (a52a2a) to light brown (b5651d) and curled at middle, dark brown (654321) at the centre; dark brown (654321) to black (000000) from below; producing dark brown (654321) pigmentation on PDA.

Material examined: China, Yunnan, Zhaotong Yiliang (27°51′45″N, 104°42′1″E, 1002.12 m), on decaying culms of bamboo, 21 July 2021, Dong-Qin Dai, DDQ02115–1 ( GMB 1373 , holotype), ex-type GMBCC1168; Ibid. DDQ02115–2 (GMB 1348), culture under the code of GMBCC1157 .

Note: The new isolates GMBCC1168 and GMBCC1157 formed a well-distinct lineage (100% MLBP, 1.00 BYPP) basal to H. pilgerianum (STMA 13455) and H. wuzhishanense (FCATAS2708, holotype) ( FIGURE 1 ). In addition, the NCBI BLASTn search of the individual ITS sequences of our new taxon is closely related to H. wuzhishanense (X469, OL467293.1), with 89.05% similarity. In LSU sequences, the closest matches were H. wuzhishanense (W2, OL615104.1),with96.37% similarity.The RPB2 sequence closest matches were H.wuzhishanense (X469, OL584221.1), with 86.51% similarity. The β-tubulin sequence closest matches were H. pilgerianum (STMA 13455, KY624315.1), with 91.15% similarity. Our isolates compared well with a recently established new species H. hongheensis E.F. Yang & Tibpromma , in which the differences are shown in TABLE 2 . The morphological differences between the other two related species and H. zhaotongensis are also listed in TABLE 2 . In addition, the phylogenetic analysis of combined LSU, ITS, RPB2 and β-tubulin sequences shown that the two strains of H. hongheensis (HKAS 122663, KUMCC 21-0452) separated well from H. perforatum (CBS 115281). However, our two strains of H. zhaotongensis (GMBCC1168, GMBCC1157) formed a robust clade basal to H. pilgerianum and H. wuzhishanense . Therefore, depending on morphological differences and phylogenic analyses, we introduce these two isolates as a distinct new species of Hypoxylon .

Figures

FIGURE 1. Phylogenetic tree derived from the best scoring RAxML analysis based on combined datasets (LSU–ITS–RPB2–β-tubulin). The tree is rooted to Xylaria arbuscula (CBS 126415), Xylaria hypoxylon (CBS 122620), Graphostroma platystomum (CBS 270.87) and Natonodosa speciosa (CLM-RV86). Bootstrap values for maximum likelihood (MLBP) and Bayesian posterior probabilities (BYPP) equal to or greater than 50% and 0.95, are given at the respective branches. Hyphen (-) means a value lower than 50 % (BS) or 0.95 (PP). Cultures from the holotype and epitype specimens are labeled as T and ET, respectively. New isolates are labeled in bold.

FIGURE 2. Hypoxylon zhaotongensis (GMB 1373, holotype). a Stromata on dead Bamboo. b Stromatal surface and ostioles. c–e Vertical sections of stromata. f Peridium. g Branching paraphyses. h Pigments of stromata in 10% KOH solution. i “J+” apical apparatus. j–n Asci in water. o Ascus in Melzer’s reagent. p–q Ascospores. r Ascospore showing germ slit. s, t Cultures on PDA from above and below. Scale bars: b–c = 100 μm; d = 250 μm; e = 300 μm; f, g, i–m, o–q = 20 μm; n = 30 μm; r = 15 μm.