Hongkongmyces changchunensis Phukhams., W.X. Su, & Y. Li, sp. nov.

Index Fungorum number: IF 559493; MycoBank number: MB 559493; Facesoffungi number: FoF 10725; Fig. 1

Etymology – The epithet reflects the locality, Changchun.

Holotype – HMJAU 60185.

Saprobic on decaying Betula twigs submerged in a freshwater stream. Sexual morph: Not observed. Asexual morph: Conidiomata 77– 188×85–174 μm diam, pycnidia scattered, semi-immersed, globose or ellipsoidal, black, coriaceous, ostiolate. Peridium 10–28 μm thick, composed of large, irregular, and dark brown cells arranged in a textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 2.6–23.5 × 1.6–4.9 μm (x̅=10×3 μm, n=20), enteroblastic, phialidic, determinate, cylindrical to subcylindrical, hyaline, thin-walled. Conidia 10–18×7–13 μm (x̅=13×10 μm, n=43), ellipsoidal, obovoid or irregular, aseptate, guttulate, hyaline, thin-walled, lacking mucilaginous sheath, turning brown at senescence stage.

Culture Characteristics – Colonies on PDA reaching 20 mm in 7 days at 20 °C, flat with entire margin, circular, grey to black, aerial mycelium becoming grey towards the edge; reverse grey-olivaceous to black, smooth.

Material examined – China, Jilin Province, Changchun District, Jingyuetan National Scenic Areas, on the submerged twigs in a stream of Betula sp. (Betulaceae), 12 May 2021, Chayanard Phukhamsakda (SWX32), (HMJAU 60185, holotype); ex-type living culture, CCMJ5008.

GenBank numbers – OL897173 (LSU), OL891809(SSU), OL996122 (ITS), OL944603 (tef1), OL944507(rpb2).

Notes –  Phylogenetic analyses of LSU, SSU, ITS and tef sequence data show that Hongkongmyces changchunensis (CCMJ5008) is related to the type species Hongkongmyces thailandicus (MFLUCC 16–0406), with good support (92% ML/0.93 BYPP; Fig. 1). Hongkongmyces changchunensis was collected from submerged substrates in a freshwater habitat in Jilin Province of China. Both species were collected from fresh water habitats, but from different country (Hyde et al. 2016). Hongkongmyces changchunensis is similar to Hongkongmyces aquaticus in having phialidic conidiogenous cells and hyaline, variable shaped conidia, but it lacks sympodial proliferations (Dong et al. 2020). Hongkongmyces changchunensis is characterized by wet, globular, mass of conidia on natural substrates after drying and smooth surfaced conidia containing multiple small bubbles. Herein, we propose a new species based on both
morphology and phylogenetic analyses.

Figure 1 – Hongkongmyces changchunensis (HMJAU 60185, holotype) a, b Appearance of conidiomata on host surface. c Vertical section through conidioma. d Ostiole canal. e Section of partial conidioma peridium. f–h Conidiogenous cells and developing conidia. i–l Developmental state of conidia. Scale bars: a=500, b=200 µm, c=100 µm, d, e=50, f, l=20 µm, g–k=10 µm