Trichoderma mianyangensis Feihu Wang & C. L. Yang, 2025

Wang, Feihu, Xu, Xiulan, Liu, Feng, Xiang, Shasha, Li, Xinyue, Liu, Yinggao & Yang, Chunlin, 2025, Four new species of Trichoderma (Hypocreaceae, Hypocreales) discovered in the staple food bamboo of pandas, MycoKeys 124, pp. 227-248 : 227-248

Trichoderma mianyangensis Feihu Wang & C. L. Yang sp. nov.

Fig. 5

Etymology.

The specific epithet is derived from the collection locality of the type specimen, Mianyang City, Sichuan Province.

Holotype.

SICAU 25-0183 .

Habitat.

On the culm of Phyllostachys sulphurea .

Description.

Sexual morph: Stromata solitary, scattered, or aggregated in small numbers (2–3), presenting a pulvinate, discoid, lrregular in shape, broad-based in attachment. Ranging in color from light yellow to nearly citrine, with diameters of 3–10 mm and thicknesses of 1–3 mm (n = 30). Surface finely tuberculate or wrinkled. Margins rounded, angular, or undulate, typically free, sides slightly retracted inward. Ostiolar dots minute, distinct, surface rarely convex. Ascomata nearly spherical, densely arranged, and numerous, measuring 220–360 × 180–270 μm (x – = 290 × 170 μm, n = 20). Ostioles flush with the surface, with apical widths of 35–58 μm and heights of 40–78 μm (n = 20). Peridium hyaline to light yellow, with a lateral thickness of 8–12 μm and a basal thickness of 11–17 μm (n = 20). Asci 82–108 × 5–7 μm (x – = 100 × 6 μm, n = 20), inclusive of a stipe 9–20 μm long, cylindrical, containing 16 - ascospores, apex slightly thickened, hyaline. Ascospores 3–6 × 3.5–4.5 μm (x – = 5 × 4 μm, n = 40), green, partially hyaline, finely spinulose, and ranging from nearly spherical to slightly ovoid in shape. Asexual morph: Conidiophores consist of an erect stipe with a 1–3 celled branch at the apex. Phialide t lageniform, ampulliform, or subglobose, measuring 4–12 × 1.5–3 μm (x – = 9 × 2 μm, n = 30). Conidia hyaline, ellipsoidal to oblong, less commonly subglobose, smooth, and measure 2.5–4 × 1.5–3 μm (x – = 3 × 2 μm, n = 40).

Material examined.

China • Sichuan Province, Mianyang City, Pingwu , Primitive Forest of Phyllostachys sulphurea ( 32°37'13.81"N, 104°31'21.63"E, Alt. 1363 m), 18 October 2024, Feihu Wang, WFH 20240092, ( SICAU 25-0183 , holotype), ex-type culture SICAUCC 25-0155 . ibid. WFH 20240092 B ( SICAU 25-0184 , paratype), living culture SICAUCC 25-0156 .

GenBank accession numbers.

SICAUCC 25-0155 ( ITS: PV 789477; tef 1 - α: PV 828330; rpb 2: PV 828322); SICAUCC 25-0156 ( ITS: PV 789478; tef 1 - α: PV 828331; rpb 2: PV 828323)

Culture characters.

Three media were tested for fungal growth: potato dextrose agar ( PDA), oatmeal agar ( SNA), and malt extract agar ( MEA), all incubated at the optimal temperature of 25 ° C. On PDA, the mycelium fully covered a 60 - mm Petri dish within 8–10 days, forming a circular colony with a regular margin and velvety to floccose surface hyphae arranged radially. Abundant aerial hyphae extended toward the margin, becoming floccose post-conidiation. By day 12, conidiation initiated around the inoculation plug, forming small white clusters that expanded peripherally while remaining white. No diffusing pigment or distinct odor was detected. On SNA, growth was slower, requiring 20 days to fully colonize the dish (colony diameter: 20 mm after 12 days). The colony remained white and transparent, with sparse mycelium on the agar surface. Central mycelia became hollow, forming a loose, white film-like structure. No pigment or odor was observed, though the inoculation site gradually greened, conidia were absent. On MEA, rapid growth covered the dish within 7–9 days, yielding a circular, transparent colony with conspicuous variation in hyphal width (no zonation). Aerial hyphae were sparse initially but thickened at distal / lateral margins over time. By day 11, conidiation initiated on aerial hyphae near the proximal margin, forming fluffy tufts that compacted into 1–3 mm pustules with, pustules remained white for 5–8 days, then turned brown. No diffusing pigment or odor was detected.

Notes.

Phylogenetically, Trichoderma mianyangensis strain SICAU 25-0183 and SICAU 25-0184 formed a distinct clade and is related to T. parahongkuii ( GDMCC 3.1019 ) in the Koningii clade, but the similarities of rpb 2 and tef 1 - α between these two species were only 94.4 % and 80.9 %, respectively. From a morphological perspective, our newly described taxon, Trichoderma mianyangensis , shares some common characteristics with T. parahongkuii isolated from soil in a Chimonanthus praecox orchard. There are certain differences in cultural characteristics between T. mianyangensis and T. parahongkuii , differences in cultural characteristics exist between T. mianyangensis and T. parahongkuii . Trichoderma mianyangensis lacks any odor, while T. parahongkuii emits a noticeable fruity scent, and the conidia of T. mianyangensis are smaller (2.5–4 × 1.5–3 μm vs. 3.6–5.1 × 2.6–3.5 μm) ( Zhao et al. 2025). Phylogenetic analysis reveals that the new taxon, T. mianyangensis ( SICAU 25-0183 ), is closely related to T. parahongkuii ( GDMCC 3.1019 ), with strong statistical support (Fig. 1 ). However, our strain differs from T. parahongkuii in the rpb 2 region amounting to 5.6 % (63 / 1130, 0 gap), 19.1 % (178 / 930, 61 gaps) differences in tef 1 - α. Pairwise nucleotide comparisons further support the distinction of T. mianyangensis . The PHI test revealed no significant recombination event between our strain and the closely related taxa (Φw = 1.00) (Fig. 2 ). These differences also support the classification of T. mianyangensis as a distinct species.

Figures

Figure 1. Phylogram generated from maximum likelihood analysis based on combined ITS, tef 1 - α and rpb 2 sequence data of Trichoderma (koningii species complex) taxa. The species determined in this study are indicated in bold red. Bootstrap values (BS) from maximum likelihood (MLBS, left) higher than 70 BS and Bayesian posterior probabilities (BYPP, right) greater than 0.90 are given at the nodes. Hyphens (-) represent support values less than 70 MLBS / 0.90 BYPP. The ex-type strains are in T.

Figure 2. The PHI test results for Trichoderma bashania, T. fargesia, T. mianyangensis, T. yaanensis, and closely related species were obtained using both LogDet transformation and splits decomposition methods. The PHI test did not find any statistically significant recombination (Φw = 1) in the data set. The new strains are represented in red and bold. “ T ” represents the type strain.

Figure 5. Trichoderma mianyangensis (SICAU 25-0183, holotype). a. Appearance of ascomata on dead host; b. Stromata; c. Ascomatal tissue in section; d. Peridium; e – h. Asci; i. Ascospores; j. Germinated ascospore; k. Culture on PDA (15 days at 25 ° C); l. Cultures on SNA (15 days at 25 ° C); m. Cultures on MEA (15 days at 25 ° C); n – p. Conidiophores and phialides (PDA 30 days at 25 ° C); q. Conidia (PDA 30 days at 25 ° C); r. Chlamydospores (PDA 30 days at 25 ° C). Scale bars: 500 µm (b); 50 µm (c); 10 µm (e – i, r); 5 µm (j, n – q).