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

Fig. 6

Etymology.

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

Holotype.

SICAU 25-0181 .

Habitat.

On the culm of Bambusa emeiensis .

Description.

Sexual morph: Not observed. Asexual morph: Conidiophores are short and simple, either erect or arising obliquely from the surface hyphae. Phialides are solitary, whorls, and often borne on one-celled lateral branches, being conical or cylindrical in shape. Conidia 3.5–5.5 × 2–3.5 μm (x – = 4 × 2.6 μm, n = 40), pale green, smooth, ovoid or ellipsoidal.

Material examined.

China • Sichuan Province, Ya’an City, Yucheng , Bambusa emeiensis industrial base ( 29°52'44.35"N, 103°5'23.37"E, Alt. 871 m), 28 April 2024, Feihu Wang, WFH 202404030, ( SICAU 25-0181 , holotype), ex-type culture SICAUCC 25-0153 . ibid. WFH 202404030 B ( SICAU 25-0182 , paratype), living culture SICAUCC 25-0154 .

GenBank accession numbers.

SICAUCC 25-0153 ( ITS: PV 789473; tef 1 - α: PV 828326; rpb 2: PV 828318); SICAUCC 25-0154 ( ITS: PV 789474; tef 1 - α: PV 828327; rpb 2: PV 828319).

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 9–10 days, forming a circular, dense colony with a regular margin and sparse surface hyphae arranged radially. By day 15, small white velvety masses appeared, later browning and producing conidia; no odor or pigment was detected. On SNA, growth was slower, requiring 15 days to cover the dish. The colony remained white with sparse aerial hyphae and no zonation, though the inoculation site gradually greened, conidia and pigments were absent. On MEA, rapid growth covered the dish in 8 days, yielding a rough-edged colony with abundant aerial hyphae that thickened at distal / lateral margins. Sporulation initiated after 10 days, forming fan-shaped patterns, no odor or pigment was observed.

Notes.

Phylogenetically, Trichoderma yaanensis strain SICAU 25-0181 and strain SICAU 25-0182 formed a distinct clade and is related to T. merleae (MST FP 3586) in the Koningii clade, but the similarities of rpb 2 and tef 1 - α between these two species were only 97.9 % and 99.5 %, respectively. Trichoderma yaanensis is classified within the Koningii clade and is phylogenetically closely related to T. merleae . Currently, there is no available morphological description for T. merleae , only molecular data have been documented, thereby rendering morphological comparisons infeasible. Phylogenetic analysis reveals that the new taxon, Trichoderma yaanensis ( SICAU 25-0181 ), is closely related to T. merleae (MST FP 3586), with strong statistical support (Fig. 1 ). However, our strain differs from T. merleae in the ITS region amounting to 11.7 % (67 / 572, 32 gap), 2.1 % (17 / 807, 0 gap) differences in rpb 2, 0.5 % (5 / 921, 0 gap) differences in tef 1 - α. Pairwise nucleotide comparisons further support the distinction of T. yaanensis . The PHI test revealed no significant recombination event between our strain and the closely related taxa (Φw = 1.00) (Fig. 2 ). Therefore, based on the phylogenetic differences, T. yaanensis is introduced as a new species within Trichoderma .

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 6. Trichoderma yaanensis (SICAU 25-0181, holotype). a. Culture on PDA (15 days); b. Cultures on SNA (15 days at 25 ° C); c. Cultures on MEA (15 days at 25 ° C); d – i. Conidiophores and phialides (PDA 30 days at 25 ° C); j. Conidia (PDA 30 days at 25 ° C). Scale bars: 20 µm (d, e); 15 µm (f); 10 µm (g – i); 5 µm (j).