Exophiala hongheensis P. X. Yu. & J. W. Guo, 2025

Yu, Peixuan, Guo, Jianwei, Jayawardena, Ruvishika S., Kakumyan, Pattana, Li, Jingxian & Yang, Jian, 2025, Exophiala hongheensis (Herpotrichiellaceae, Chaetothyriales, Eurotiomycetes), a new endophytic species on Amomum tsao-ko in Yunnan, China, Phytotaxa 691 (3), pp. 247-259 : 254

Exophiala hongheensis P. X. Yu. & J. W. Guo , sp. nov. Fig. 2

Index Fungorum no: IF902267

Holotype: HKAS 134914

Etymology: “hongheensis ” refers to Honghe, a prefecture of Yunnan Province in southwest China, from where the holotype was collected.

Endophytic on the fruit of Amomum tsao-ko ( Zingiberaceae ). Asexual morph: on PDA media. Mycelium superficial. Hyphae 1.2–3.0 µm (x̅ = 1.74 μm, n = 10) wide, pale olive-green, smooth, irregularly septate, thin-walled, branched, hyphal coil formed from the hyphal tips toward the middle of the hyphae, with rope-like hyphal strands fused as extensive circular coils and produces a membrane. Conidiophores cylindrical, pale to brown, micronematous to semimacronematous, and often reduced to conidiogenous cells. Conidiogenous cells length 2–10 µm (x̅ = 4.2 μm, n =15), wide 1.3–3.5µm (x̅ = 2.6 μm, n =15), slightly differentiated from the mycelium, borne on the apical or lateral part of the mycelium, terminal or intercalary, variable in shape, urceolate to elongate, clavate, with an obtuse base. Conidia 2–6 × 1.4–3.2 µm (x̅ = 4 × 2 μm, n = 15), diverse in shape, long ellipsoid, teardrop-shaped, pear-shaped, smooth wall, light olive-green to light gray. Sexual morph: undetermined.

Culture characteristics: Colonies reaching 6 mm in 30 days on PDA medium at 27 ± 3 °C; flat, spreading, circular, entire margin, subhumid, sparse aerial mycelium. The mycelium of the colony is white in the pre-growth stage, and from the seventh day onwards when the colony grows to a diameter of 2.5 cm, grey-green pigmentation is produced from the centre of the colony. After 7 days, olive-black in the centre with olive-grey edges.

Material examined: CHINA, Yunnan Province, Honghe Prefecture, Jingping County: 22°46'29"N 103°31'31"E, elevation 1308 m altitude, isolated as an endophyte from the fruit of Amomum tsao-ko , 15 February 2022, P.X. Yu, 408, dried-culture: HKAS 134914 (holotype), ex-type living culture: KUNCC24-17778. Additional specimens examined: CHINA, Yunnan province, Honghe Prefecture, Yuanyang County: 23°0'1"N 102°59'52"E, elevation 1820 m altitude, isolated as an endophyte from the fruit of Amomum tsao-ko , 15 February 2022, P.X. Yu, 401, dried-culture: HKAS 134913, living culture: KUNCC24-17779.

Notes: Based on the BLAST search results in the NCBI nucleotide database, the sequences with the highest similarity to our species were as follows: the ITS region matched most closely with Exophiala lecanii-corni (GenBank OW983193 ; Identities = 576/592 (97%)), the LSU region with Exophiala mali (GenBank MW175381 ; Identities = 846/849 (99%)), and the SSU region with Exophiala castellanii (GenBank NG_062076; Identities = 768/775(99%)). Exophiala hongheensis is phylogenetically related to E. lavatrina , E. mali , and E. lecanii-corni . The raised, tufted, or radially folded colonies in the centre of E. lavatrina differ from those of E. hongheensis ( Borman et al. 2017) .

Additionally, E. lavatrina exhibits torulose mycelium and larger conidia (4.5–7 × 2.5–4 µm) than E. hongheensis (2–6 × 1.4–3.2 µm). Exophiala mali forms chains of disarticulating conidia ( Crous et al. 2020) and has larger conidia (4–7 × 2.5–3 µm) than E. hongheensis (2–6 × 1.4–3.2 µm). Exophiala lecanii-corni is most similar to E. hongheensis in conidia size (3.3–5.9 × 1.5–2.4 µm). However, E. lecanii-corni produces conidia through budding cells ( De Hoog 1997), while conidiogenous cells of E. hongheensis are lateral branches of 2–10 µm in length, and the budding cells of E. lecanii-corni are typically swollen into wide ellipsoids, while the conidiogenous cells of E. hongheensis are elongated. Therefore, based on morphological and molecular evidence, E. hongheensis is introduced herein as a new species on Amomum tsao-ko from Yunnan Province, China.

Figures

FIGURE 2. Exophiala hongheensis (HKAS 134914, holotype) (A) Colony at 25 °C on PDA after 14 days (surface on left; reverse on right). (B, C) Conidiophore appearance. (D) Mycelium and conidia. (E, F) Hyphae coil. (G) Mycelium and conidiogenous cells. (H–J) Conidiogenous cells giving rise to conidia. (K, L) Conidial apparatus with conidia. (M–Q) Conidia. Scale bars: D = 50 μm; E, F = 20 μm; G, H, J = 10 μm; I, K–Q = 5 μm.