Seriascoma honghense H.B. Jiang, Phookamsak & K.D. Hyde, sp. nov.

Index Fungorum number: IF 558194; MycoBank number: MB 558194; Facesoffungi number: FoF 09765; Fig. 1

Etymology – The specific epithet “honghense” refers to the collection site (Honghe County), of which the new species was collected.

Holotype – KUN-HKAS 112013

Saprobic on dead bamboo branches. Sexual morph Undetermined. Asexual morph Coelomycetous. Conidiomata pycnidial, 60–90 μm high, 320–510 μm diam., solitary to gregarious, immersed under cortex to superficial, raised, black, elongate-conical, 1- to multi-loculate, glabrous. Locules 45–300 μm diam., 30–70 μm high, clustered, arranged in rows, dark brown, subglobose to ampulliform. Peridium 12–20 μm thick, thin- to thick-walled, of unequal thickness, thick at the sides, thin at the base, composed of host and fungal tissue, with several layers of dark brown to brown, pseudoparenchymatous cells of textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 5.5–6.5 × 2–3 μm (x̅= 6 × 5 μm, n = 20), enteroblastic, phialidic, determinate, discrete, subglobose or cylindrical to conical, hyaline, aseptate, smooth-walled. Conidia 4.5–5 × 2 μm (x̅= 5 × 2 μm, n = 20), subglobose to oblong, hyaline, bi-guttulate, aseptate, smooth-walled.

Culture characteristics – Conidia germinating on PDA within 24 h. Colonies growing fast on PDA, reaching 10 mm in 1 week at room temperature, under the normal light, cottony, circular, raised, grayish to dark brown from above and below. Mycelium superficial to immersed in media, with branched, septate, smooth hyphae.

Material examined – CHINA, Yunnan Province, Honghe Autonomous Prefecture, Honghe County, a roadside bamboo (23°13′30.42″ N, 102°20′58.85″ E, altitude 1682 m), on dead branches of bamboo in a terrestrial environment, 28 October 2020, H.B. Jiang, HONGHE008 (KUN-HKAS 112013, holotype); HMAS 249946 (isotype), ex-type living culture, KUMCC 21-0007.

GenBank numbers – ITS = MW981351, LSU = MW981347, SSU = MZ325471, RPB2 = MZ325473, TEF1-α = MZ325472.

Notes – Seriascoma honghense matches the typical characteristics of the coelomycetous asexual morph of Seriascoma (Fig. 1). However, it differs from Seriascoma didymospora in its multi-loculate, flat conidiomata and a thinner peridium. Based on the present phylogeny, S. honghense is determined to be a sister to S. didymospora with 98% ML, 0.96 PP statistical support (Fig. 2). Pairwise nucleotide comparison of ITS and TEF1-α also showed that S. honghense differs from S. didymospora in 36/483 bp (7.45%) and 26/947 bp (2.75%), respectively.

Figure 1 – Seriascoma honghense (KUN-HKAS 112013, holotype). a Conidiomata on surface of dead bamboo branches. b, d Vertical section of conidioma. c Wall of conidioma. e Ampulliform locule of conidioma. f–i Conidiogenous cells bearing conidia. j Conidia. k, l Culture frontage and reverse. Scale bars: b, d=100 μm, e=50 μm, c=20 μm, f–j=5 μm

Figure 2 – Phylogram generated from maximum likelihood analysis based on combined ITS, LSU, SSU and TEF1-α sequence data. Twenty-three strains are included in the combined gene analyses comprising 3865 characters after alignment (643 characters for ITS, 853 characters for LSU, 1438 characters for SSU, 931 characters for TEF1-α). Ohleria modesta (MGC and OM) is used as the outgroup taxon. The tree topology of the Bayesian analysis was similar to the maximum likelihood analysis. The best RAxML tree with a final likelihood value of − 13136.916046 is presented. The matrix had 883 distinct alignment patterns, with 33.71% undetermined characters or gaps. Estimated base frequencies were as follows: A=0.241326, C=0.251489, G=0.273232, T=0.233953; substitution rates AC=1.629497, AG=2.743632, AT=1.443415, CG=0.989741, CT=7.278242, GT=1.000000; gamma distribution shape parameter α=0.150194. Bootstrap values for maximum likelihood equal to or greater than 70% and Bayesian posterior probabilities equal or greater than 0.95 BYPP are placed above or below the branches. Ex-type strains are in bold and newly generated sequence is in blue