Seriascoma acutispora Senan., B. Xu & K.D. Hyde, sp. nov.

Index Fungorum number: IF 900417; MycoBank number: MB 900417; Facesoffungi number: FoF 14171; Fig. 1

Etymology – based on the acute ends of ascospores.

Saprobic on dead branches of an unidentified plant. Sexual morph: Clypeus spread over the ascostromata, comprised of highly pigmented, tightly-packed cells. Ascostromata 300–330 μm high, 475–550 μm diam., solitary, scattered, uniloculate, erumpent in host, immersed beneath the clypeus, conical to pyriform, coriaceous, with a central ostiole, dark brown to black, apapillate. Peridium 10–15 μm, thin, thinner at the base, composed of several layers of very small, brown to dark brown cells of textura angularis, combined with plant epidermis cells. Hamathecium 1.4–2.8 μm wide, comprising numerous, branched, filiform, septate pseudoparaphyses and longer than asci. Asci 100–110×20–30 μm (x=102×24 μm, n=20), 8-spored, bitunicate, fissitunicate, cylindric-clavate, long pedicellate, apically rounded, with well-developed ocular chamber. Ascospores 33–40×7–9 μm (x=35×8 μm, n=20), biseriate, didymosporous, slightly narrow, elongated fusiform, with acute ends, hyaline, slightly constricted at the septum, straight to curved, upper cell slightly wider than lower cell, smooth-walled, surrounded by a gelatinous sheath, 4 or more guttulate. Asexual morph: Undetermined.

Culture characters – Colonies on PDA reaching 1 cm diam. after 10 days in dark at 25 °C, circular, umbonate, filiform margin, with greenish black mycelia, centre crowed with grey aerial, mycelial clots; reverse black.

Material examined – Thailand, Chiang Mai Province, Saluang Mae Rim District, on dead twigs of Bambusa sp., 17 February 2019, I.C. Senanayake, S3 23–2 (MHZU 22-0143, holotype), ex-type cultures ZHKUCC 22-0273, ZHKUCC 22-0274.

GenBank numbers – LSU: OR164965, OR164966, ITS: OR164937, OR164938, rpb2: OR166288, OR166289, tef1-α: OR166279.

Notes – The combined gene analysis of ITS, LSU, rpb2 and tef1-α (Fig. 2) showed that our new strains clustered with the type strain of Seriascoma yunnanense forming a distinct clade with ML/BI=94%/0.90 statistical support. There are 11.62%, 2.64%, 12.26% and 6.2% base pair differences in ITS, LSU, rpb2 and tef1-α sequences between our isolate and Seriascoma yunnanense respectively.

Figure 1 – Seriascoma acutispora (MHZU 22-0143, holotype). a Appearance of ascomata on the dead woody twigs of Bambusa sp. b Vertical cross section of ascoma. c Peridium. d, e Asci. f–i Ascospores. j Pseudoparaphyses. k Surface view of colony on PDA. l Reserve view of colony on PDA. Scale bars: b=100 µm, d, e=25 µm, c, f–i=15 µm

Figure 2 – Phylogram generated from maximum likelihood analysis based on combined ITS, LSU, rpb2 and tef1-α sequence data which comprised 3137 characters (ITS=516, LSU=870, rpb2=1,076, tef1-α=516). The best scoring RAxML tree with a final likelihood value of − 19,614.282564 is presented. The matrix had 1299 distinct alignment patterns, with 17.87% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.234151, C=0.279510, G=0.258584, T=0.227755; substitution rates: AC=1.581558, AG=4.062963, AT=1.691894, CG=1.106792, CT=8.475079, GT=1.0; gamma distribution shape parameter α=0.191641. Bootstrap support for maximum likelihood (ML)
equal to or greater than 50% and clade credibility values greater than 0.90 (the rounding of values to 2 decimal proportions) from Bayesian inference analysis are labelled at each node. Ex-type strains are in bold, while the new isolate is indicated in blue bold. The tree is rooted to Westerdykella ornata (CBS 379.55)