Neohelicomyces subtropicus J. Ma & Y. Z. Lu, 2025

Peng, Tao, Lu, Yong-Zhong, Bai, Song, Zhang, Jing-Yi, Xiao, Xing-Juan, Wu, Na & Ma, Jian, 2025, Novel Helicosporium and Neohelicomyces (Tubeufiaceae, Tubeufiales) species from terrestrial habitats in China and Thailand, MycoKeys 112, pp. 81-101 : 81-101

Neohelicomyces subtropicus J. Ma & Y. Z. Lu sp. nov.

Fig. 4

Holotype.

HKAS 128847 .

Etymology.

‘‘ subtropicus ’’ named after the climate from which the holotype was found.

Description.

Saprobic on decaying wood in a forest. Sexual morph Undetermined. Asexual morph Hyphomycetous, helicosporous. Colonies on natural substrate superficial, effuse, solitary, gregarious, white to pale brown. Mycelium partly immersed, partly superficial, composed of pale brown to brown, branched, septate, guttulate, smooth. Conidiophores up to 420 μm long, 2.5–5.5 μm wide (x ̄ = 3.5 μm, n = 30), macronematous, mononematous, erect, solitary or in a group, cylindrical, long or short, tapering at tip, flexuous, mostly branched, septate, slightly constricted at septa, hyaline to pale brown at base, becoming hyaline toward apex, smooth-walled, thick-walled. Conidiogenous cells 10.5–19.5 μm long, 2–5.5 μm wide (x ̄ = 15.5 × 3.5 μm, n = 35), holoblastic, monoblastic to polyblastic, integrated, intercalary or terminal, cylindrical or subcylindrical, with a denticulate protrusion, truncate at apex after conidial secession, hyaline to pale brown, smooth-walled. Conidia solitary, acropleurogenous, helicoid, dry, tapering towards the rounded ends, developing on tooth-like protrusions, 14.5–16.5 μm diam. and conidial filament 1.5–3 μm wide (x ̄ = 15.5 × 2 μm, n = 25), 87–132 μm long (x ̄ = 110.5 μm, n = 25), aseptate, tightly coiled 2–2 3 / 4 times, becoming loosely coiled when the conidia are young in water and not becoming loose when the conidia mature in water, guttulate, hyaline, smooth-walled.

Culture characteristics.

Conidia germinated on PDA, producing germ tubes within 12 hours. Colonies on PDA reached a diameter of 44 mm after 46 days of incubation at 25 ° C, exhibiting an irregular shape with a flat surface and undulate margin, pale brown to black brown in PDA medium.

Material examined.

China • Guizhou Province, Qiannan Buyi and Miao Autonomous Prefecture, Libo County , on rotting wood in a terrestrial habitat, 10 April 2022, Jian Ma, MN 2 ( HKAS 128847 , holotype), ex-type living culture GZCC 23–0076 ; • Ibid., MN 2.1 ( GZAAS 23–0632 , paratype), ex-paratype living culture GZCC 23–0147 .

Notes.

Phylogenetically, our new isolates ( GZCC 23–0076 and GZCC 23–0147 ) formed a sister clade with N. helicosporus ( GZCC 23–0633 and GZCC 23–0634 ) and N. hyalosporus ( GZCC 16–0086 ) (Fig. 1 ). A comparison of the ITS, LSU, tef 1 - α, and rpb 2 sequence data between our strain ( GZCC 23–0076 ) and N. hyalosporus ( GZCC 16–0086 ) revealed nucleotide base differences of 29 / 515 bp (5.6 %, including 12 gaps), 1 / 842 bp (0.1 %, without gap), 21 / 912 bp (2.3 %, including one gap), and 22 / 1045 bp (2.1 %, without gap), respectively. Morphologically, our newly collected specimen ( HKAS 128847 ) differs from N. helicosporus ( HKAS 134923 ) and N. hyalosporus ( HKAS 97441 ) in having longer conidiophores (up to 420 μm vs. 105–199 μm and 210–290 μm, respectively) ( Lu et al. 2018 b; Ma et al. 2024 a). Additionally, Neohelicomyces subtropicus exhibits branched conidiophores, which are absent in N. helicosporus and N. hyalosporus ( Lu et al. 2018 b; Ma et al. 2024 a). Therefore, we propose Neohelicomyces subtropicus as a new species based on morphological comparison and multi-gene phylogenetic analysis.

Figures

Figure 1. Phylogram generated from the best scoring of the RAxML tree based on the combined LSU, ITS, tef 1 - α, and rpb 2 sequence dataset, indicating Helicosporium and Neohelicomyces species. Botryosphaeria agaves (MFLUCC 10–0051) and B. dothidea (CBS 115476) were selected as outgroup taxa. Bootstrap support values from maximum likelihood (ML) equal to or greater than 75 % and Bayesian posterior probabilities (PP) equal to or greater than 0.95 are shown near the nodes as ML / PP, respectively. “ T ” denotes ex-holotype strains. New species are in bold blue.

Figure 4. Neohelicomyces subtropicus (HKAS 128847, holotype) a colonies on the host surface b – e conidiophores, conidiogenous cells with conidia f, g, i conidiogenous cells j – n conidia h germinated conidium o, p surface and reverse colonies on PDA after 46 days of incubation at 25 ° C. Scale bars: 100 μm (b); 20 μm (c – h, j – m); 10 μm (i, n).