Hongkongmyces xishuangbannaensis Y.X. Shu, W. Dong & K.D. Hyde, in Dong et al., Fungal Diversity (2025)

Index Fungorum number: IF 902616; MycoBank number: MB 902616; Facesoffungi number: FoF 17154; Fig. 1

Etymology – refers to Xishuangbanna City from where the fungus was collected.

Holotype – MHZU 24-0587

Saprobic on bamboo submerged in freshwater habitats. Sexual morph: undetermined. Asexual morph: Conidiomata 180–210 µm high, 240–270 µm diam. (x̄ = 195 × 260 µm, n = 5), pycnidial, scattered, semi-immersed to superficial, subglobose or ellipsoidal, unilocular, black, coriaceous, central ostiolate, apapilate. Peridium 20–30 µm thick, comprising several layers of large, thin-walled, compressed cells of textura angularis, dark brown to black in the outer layers, subhyaline inward. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 7–10 × 3–6 µm, enteroblastic, phialidic, determinate, integrated, subcylindrical or narrowly obpyriform, hyaline, smooth, thin-walled, forming from the inner wall cells. Conidia 11–16 × 9–12 µm (x̄ = 12.5 × 11.5 µm, n = 20), globose, subglobose or obovoid, or irregular-shaped, hyaline, aseptate, minutely guttulate, smooth, thin-walled.

Culture characteristics – conidia germinating on MEA within 48 h. Colony reaching up to 20 mm on PDA after 20 days at room temperature, grey from above, pale brown from below, surface rough, dry, raised, edge entire.

Material examined – China, Yunnan Province, Xishuangbanna, on submerged bamboo in a lake, 29 September 2022, Y.X. Shu, BN1b (MHZU 24-0587, holotype); ex-type culture, ZHKUCC 24-1067; ibid., (MHZU 24-0588, isotype); ex-isotype culture, ZHKUCC 24-1068.

GenBank accession numbers – ZHKUCC 24-1067 = ITS: PQ285646, LSU: PP937766, SSU: PP937770, tef1-a: PQ299037; ZHKUCC 24-1068 = ITS: PQ303760, SSU: PP937769, tef1-a: PQ614178.

Notes – the multi-locus phylogenetic analysis of a combined LSU, SSU, ITS, and tef1-a sequence dataset indicates that Hongkongmyces xishuangbannaensis forms a well-supported subclade with H. kokensis (Fig. 2). Hongkongmyces xishuangbannaensis resembles H. kokensis in the presence of subglobose or ellipsoidal, ostiolate conidiomata, phialidic conidiogenous cells, and hyaline conidia (Boonmee et al. 2021). Hongkongmyces xishuangbannaensis can be distinguished from H. kokensis in having different shape of conidia (irregular-shaped vs. subglobose to obovoid), and smaller conidiogenous cells (reaching 10 µm long and 6 µm wide in H. xishuangbannaensis compared to reaching 21 µm long and 12 µm wide in H. kokensis) (Boonmee et al. 2021). A comparison of LSU, SSU, ITS, and tef1-a base pairs reveals that H. xishuangbannaensis differs from H. kokensis by 2/865 bp (0.23%) in LSU, 57/1403 bp (4.06%) with 8 gaps in ITS, and 17/943 bp (1.80%) in tef1-a. Therefore, H. xishuangbannaensis is identified as a novel species within Hongkongmyces.

Figure 1 – Hongkongmyces xishuangbannaensis (MHZU 24-0587, holotype). a, b Appearance of black conidiomata on host. c Vertical section of pycnidium. d Peridium. e–h Conidiogenous cells with conidia. i–m Conidia. n, o Colony on MEA (front and below). Scale bars: c = 100 µm, d = 20 µm, e–h = 5 µm, i–m = 10 µm.

Figure 2 – Maximum likelihood consensus tree inferred from the combined LSU, SSU, ITS, tef1-a multiple sequence alignments. Bootstrap support values for maximum likelihood (ML, first value) equal to or greater than 80% and Bayesian posterior probabilities from MCMC analyses (BYPP, second value) equal to or greater than 0.95 are given above the nodes. The scale bar indicates expected changes per site. The tree is rooted to Gloniopsis subrugosa CBS 123346 and Hysterobrevium smilacis CBS 114601. Ex-type strains are indicated with “T”. The newly generated sequences are indicated in red.