Hypoxylon inaequale S.C. He & Jayaward., sp. nov.

Index Fungorum number: IF 900071; MycoBank number: MB 900071; Facesoffungi number: FoF 13393; Fig. 1

Etymology –  Based on the inequilateral spore character.

Holotypus –  HKAS123207.

Saprobic on dead stem plant from Itoa orientalis. Sexual morph: Stromata 40–50 × 20–30 mm (M =45 × 25 mm, n=15), glomerate, fawn, sessile, gregarious or solitary, with white ostioles. Perithecia 250–300 × 260–450 μm (x̄=275×365 μm, n=15), spherical to obovoid, completely immersed in stromata. Ostioles 90–120 μm diam, umbilicate, white. Paraphyses 2.5 × 3.1 μm wide, copious, filiform, aseptate, unbranched. Asci 132 − 153 × 9–11 μm (x̄=142×10 μm, n=10), cylindrical, 8-spored, uniseriate, stipitate, with apical apparatus colorless in Melzer’s reagent. stipe 40–112 μm (n=10). Ascospores 9.8–11.8×5.0–5.9 μm (x̄=10.45×5.45 μm n=20), pale dark brown when immature, becoming dark brown with age, ellipsoid-inequilateral with round ends, unicellular, with two round guttulae, obliquely arranged. Asexual morph: Not observed.

Culture characteristics –  Culture was made from germinating ascospores and was incubated with PDA media at 25 ℃, reaching 2.2–2.4 cm in 24 days. The colony white, occasionally raised, fluffy, with dense mycelia, umbonate margin, reverse chrome yellow.

Material Examined –  China, Yunnan Province, Kunming City, Kunming Institute of Botany, Chinese Academy of Sciences, on Itoa orientalis Hemsl. (Salicaceae), 30 August 2021,Shu-Cheng He, HSC20B (HKAS123207, holotype); ex-type living culture, KUNCC22-10798.

GenBank numbers –  ON329812 (ITS).

Notes –  Based on the multi-gene phylogenetic results, our specimen is closely related to Hypoxylon delonicis (Perera et al. 2020). Based on morphology, our strain differes from Hypoxylon delonicis by having wider asci and shorter and woder ascospores. Based on a megablast search of the NCBIs nucleotide database using the multi-gene sequence, the highest similarities ITS (GenBank KU683766; Identities=480/541(89%), Gaps=17/541(3%)), tub2 (GenBank AY951740; Identities=1126/1265(89%), other species of Hypoxylon delonicis with strong bootstrap support (82/0.99, Fig. 2). We identified Hypoxylon inaequale as a new species of Hypoxylon.

Figure 1 – Hypoxylon inaequale. (HKAS123207, holotype) a Substrate. b, c Stromata showing ostioles. d, e Vertical section through stromata. f Perithecium. g Peridium. h–k asci. l paraphyses. m–q Immature to mature ascospores. r, s Germinating ascospores. t, u Culture on PDA. Scale bars: e–f, h=200 μm, g=100 μm i–l=50 μm, m–s=5 μm

Figure 2 –  Phylogram generated from maximum likelihood analysis based on combined ITS, tub2 sequence data representing Hypoxylaceae in Xylariales. Related sequences are taken from (Cedeño– Sanchez 2020) and additions according to the BLAST searches in NCBI. Seventy-two strains are included in the combined analyses which comprised 1654 characters (532 characters for ITS,1122 characters for tub2) after alignment. Biscogniauxia nummularia (MUCL 51,395) and Annulohypoxylon annulatum (CBS 140775) in Xylariales were used as the outgroup taxa. Bootstrap support values for ML≥70% are given above the nodes (left side). Bayesian posterior probabilities≥0.95 are given above the nodes (right side). Ex-type strains are in bold and newly generated species is in red