Sequencing and Phylogenetic Analysis
The SSU, ITS, and LSU regions of strains NCYU-111LJ2-2A1 (BCRC FU31851), NCYU-111FX3-1D2, and NCYU-108L1-6 (BCRC FU31431) were successfully sequenced in this study. The lengths of these sequences varied, with the SSU sequences ranging from 2429 to 2867 bp, ITS from 536 to 543 bp, and LSU from 853 to 916 bp. All sequences obtained in this study have been uploaded to DDBJ (TABLE 1, LC794304–LC794309). Phylogenetic analysis showed that these three strains formed a highly supported clade (100/1), clustering as sister groups with Flammispora bioteca (Savoryellomycetidae, incertae sedis), and were positioned at the basal node of Savoryellomycetidae (Fig. 1). Notably, the similarity of the SSU sequences of these strains to the type strain of Flammispora bioteca, BCC13367, which has only SSU sequences available, ranged from 56.5–73.1%. Additionally, the SSU, ITS, and LSU regions of NCYU-108L1-6 showed similarities of only 74.4–74.5%, 93.2–93.4%, and 92.7% to NCYU-111LJ2-2A1 and NCYU-111FX3-1D2, respectively. Therefore, based on DNA evidence, these three strains are recognized as a new genus, Gohteikhimyces, distinct from the genus Flammispora, and they include two new species, namely, Gohteikhimyces bactrodesmioides and Gohteikhimyces taroides.
Taxonomy
Gohteikhimyces J.H. Ou, S.Y. Hsieh & C.H. Kuo, gen. nov.
Index Fungorum number
IF901621
Type species: Gohteikhimyces bactrodesmioides J.H. Ou, S.Y. Hsieh & C.H. Kuo, described below.
Etymology
In honor to Dr. Teik-Khiang Goh, with his major contribution to the taxonomy of hyphomycetes.
Phylogenetic position
Eukaryota; Fungi; Dikarya; Ascomycota; Pezizomycotina; Sordariomycetes; Savoryellomycetidae, incertae sedis; Gohteikhimyces.
Description: Species lignicolous and saprobic in freshwater habitats. Asexual morph hyphomycetous: Colonies on natural substratum effuse, black, somewhat glistening. Setae absent, Hyphopodia absent. Mycelium partly immersed, partly superficial, composed of septate, branched, hyaline to pale brown, smooth, moderately thick-walled hyphae. Conidiomata absent. Conidiophores absent or micronematous to semi-macronematous, mononematous, short, arising from superficial hyphae, subhyaline, simple, septate, smooth-walled. Conidiogenous cells borne directly on sub-immersed hyphae or on short conidiophores, terminal, integrated, holoblastic, monoblastic, thin-walled, subhyaline, determinate or sometimes percurrently regenerating. Conidia acrogenous, solitary, dry, dematiaceous, broadly cymbiform or ellipsoidal to obovoid, conical or rounded at the distal end, tapering to a distinctly paler, cuneiform basal cell, thick-walled, 3–4-euseptate, with thickening or banding at the septum and a conspicuous central septal pore connecting sac-like cytoplasm of adjacent cells, penultimate cell usually smaller than the distal and central cells. Conidial secession rhexolytic, usually with distinct frills of torn conidiogenous cells at the base.
Notes: Gohteikhimyces resembles Endophragmiella B. Sutton by its conidiophores that regenerate percurrently, producing dematiaceous euseptate conidia that secede rhexolytically. However, the latter differs in having macronematous conidiophores which are branched and bear conspicuous conidiogenous cells (Hughes 1979). Conidia of Gohteikhimyces resemble those of Bactrodesmium with accentuated septa, but the latter are produced in sporodochial conidiomata. In phylogenetic analysis, Gohteikhimyces forms a highly supported sister group with Flammispora, which is also found on plant substrates in aquatic environments. However, Flammispora does not undergo asexual reproduction either on natural substrates or in culture (Pinruan et al. 2004), distinguishing it from the genus Gohteikhimyces.
Gohteikhimyces bactrodesmioides J.H. Ou, S.Y. Hsieh & C.H. Kuo, sp. nov. (Figs. 2–5)
Index Fungorum number
IF901622
Etymology: bactrodesmioides, referring to the morphology of the conidia which resembles those of Bactrodesmium species.
Description
Asexual morph hyphomycetous. Colonies on natural substratum effuse, black, somewhat glistening. Mycelium partly immersed, partly superficial, composed of septate, branched, hyaline to pale brown, smooth-walled, moderately thick-walled hyphae. Conidiomata absent. Conidiophores absent or micronematous to semi-macronematous, mononematous, short, arising from sub-immersed hyphae, subhyaline, simple, sparsely and closely septate, smooth-walled. Conidiogenous cells discrete and borne directly from sub-immersed hyphae or on short hypha-like conidiophores, terminal, integrated, holoblastic, monoblastic, thin-walled, subhyaline, determinate or sometimes percurrently regenerating. Conidia 28–41(–46) µm × (17–)19–23.5 µm (x̄ = 40.7 × 20.4 µm, n = 53), acrogenous, solitary, dry, dematiaceous, broadly cymbiform or ellipsoidal to obovoid, broadly conical or rounded at the distal end, tapering to a distinctly paler, cuneiform basal cell, straight or sometimes slightly curved, thick-walled, smooth, 3–4-euseptate, with thickening at the septum and a conspicuous central septal pore connecting sac-like cytoplasm of adjacent cells, penultimate cell usually smaller than the distal and central cells. Conidial secession rhexolytic, usually with distinct frills of torn conidiogenous cells at the base. Sexual morph unknown.
Typification: TAIWAN, Chiayi County: Lijia Village, Alishan Township (23.460−120.710, elevation 1084 m a.s.l.) on decorticated wood submerged in a freshwater stream, 2 May 2022, leg. Chang-Hsin Kuo, NCYU-111LJ2-2A1 (holotypus, TNM F0037702); ex-type living culture: BCRC FU31851; available gene sequences: ITS = LC794305, LSU = LC794305, SSU = LC794308. TAIWAN, Taoyuan City: Fuxing District, 56K on the Northern Cross-Island Highway (24.651−121.423, elevation 1118 m a.s.l.), on decorticated wood of Acer serrulatum Hayata (Aceraceae) submerged in a freshwater stream, 14 May 2022, leg. Chang-Hsin Kuo, NCYU-111FX3-1D2 (paratypus, TNM F0037703); available gene sequences: ITS = LC794304, LSU = LC794304, SSU = LC794307.
Known distribution
Known only from the type locality (Taiwan).
Notes
The species epithet for this fungus is proposed due to its resemblance to Bactrodesmium, and is based on the two strains collected from different localities in Taiwan, with a little intra-specific variation. Conidia from the holotype (NCYU-111LJ2-2A1) have a dimension of 27.5–46 × 19–23.5 µm (x̄ = 41.8 × 21.6 µm, n = 24) and those from the paratype (NCYU-111FX3-1D2) measured 29–44.5 × 17–21 µm, x̄ = 39.6 × 19.2 µm, n = 29). Under the SEM, conidial wall of strain NCYU-111FX3-1D2 appears slightly rough-walled (Fig. 5d), however, this feature is not visible under the light microscope. Both strains of G. bactrodesmioides were collected at intermediate altitudes (ca. 1100 m a.s.l.) in the subtropical regions (northern and middle part) of Taiwan island.
Gohteikhimyces taroides J.H. Ou, S.Y. Hsieh & C.H. Kuo, sp. nov. (Figs. 6, 7)
Index Fungorum number
IF901623
Etymology: taroides, referring to the morphology of the conidia which resembles the rhizomes of taro (Colocasia esculenta).
Description
Asexual morph hyphomycetous. Colonies on natural substratum effuse, black, somewhat glistening. Mycelium partly immersed, partly superficial, composed of septate, branched, hyaline to pale brown, smooth-walled, moderately thick-walled hyphae. Conidiomata absent. Conidiophores absent or micronematous to semi-macronematous, mononematous, short, arising from sub-immersed hyphae, subhyaline, simple, sparsely and closely septate, smooth-walled. Conidiogenous cells discrete and borne directly from sub-immersed hyphae or on short, hypha-like conidiophores, integrated, terminal, holoblastic, monoblastic, thin-walled, subhyaline, sometimes percurrently regenerating. Conidia 42–50.5 × 18.5–23 µm (x̄ = 47 × 20.8 µm, n = 22), acrogenous, solitary, dry, dematiaceous, ellipsoidal, broadly cymbiform or mitriform, rarely obovoid, usually conical at the distal end, tapering to a distinctly paler, cuneiform basal cell, usually slightly curved or sometimes slightly sigmoid, thick-walled, smooth, 3–4-euseptate, with thickening at the septum and a conspicuous central septal pore connecting sac-like cytoplasm of adjacent cells, penultimate cell usually smaller than the distal and central cells. Conidial secession rhexolytic, usually with distinct frills of torn conidiogenous cells at the base. Sexual morph unknown.
Typification: TAIWAN. Kaohsiung City: Taoyuan District, 20 Provincial Highway (on the Southern Cross-Island Highway), Jianshan Village (23.102−120.688, elevation 454 m a.s.l.), on decaying wood submerged in a freshwater stream, 17 November 2019, leg. Chang-Hsin Kuo, NCYU-108L1-6 (holotypus, TNM F0037704); ex-type living culture: BCRC FU31431; available gene sequences: ITS = LC794306, LSU = LC794306, SSU = LC794309.
Known distribution
Known only from the type locality (Taiwan).
Notes
The species epithet for this fungus is proposed due to its resemblance to taro. It is proposed as a second species in the genus based on a single specimen collected from the southern, tropical region of Taiwan (Kaohsiung City) at a lower altitude (454 m a.s.l.). It differs from G. bactrodesmioides in conidial morphology. The two species are also distinct due to the low similarity in their sequences of LSU, SSU and ITS segments. Conidia of G. taroides (x̄ = 47 × 20.8 µm) are distinctly larger than those of G. bactrodesmioides (x̄ = 40.7 × 20.4 µm). Moreover, although conidia of all the three strains are similar in shape, being more or less ellipsoidal or broadly cymbiform, the conidia of G. taroides are more curved or sometimes sigmoid in contour, more attenuated at the apex, relatively more elongated in shape and hence appear mitriform. The differences in conidial shape between G. taroides and G. bactrodesmioides are also apparent under the SEM (Figs. 5, 7). Comparable to that of G. bactrodesmioides, the conidial wall of G. taroides is also slightly rough-walled but this feature is not visible under the light microscope. A diagrammatic representation for comparison of the two Gohteikhimyces is given in Fig. 8.