Trichoderma nigricans C.L. Zhang, 2023

Zhao, Rui, Mao, Li-Juan & Zhang, Chu-Long, 2023, Three new species of Trichoderma (Hypocreales, Hypocreaceae) from soils in China, MycoKeys 97, pp. 21-40 : 21

Trichoderma nigricans C.L. Zhang sp. nov.

Fig. 2

Etymology.

The Latin specific epithet " nigricans " refers to the "blackish green" color of the mass of conidia.

Diagnosis.

Phylogenetically, T. nigricans was found to form a distinct clade and was closely related to T. atroviride , T. paratroviride , T. obovatum , and T. uncinatum (Fig. 1 ). In terms of growth characteristics, T. nigricans was observed to have a larger colony radius on CMD after 72 h, and its mycelium covered the plate at both 25 °C and 30 °C. On PDA, T. nigricans grew faster than T. atroviride , T. paratroviride , T. obovatum , and T. uncinatum at 25 °C, with its mycelium also covering the plate.

Type.

China: Shandong Province, Dezhou City , 37°21'07"N, 116°23'40"E, 5 m alt., isolated from soils of peach rhizosphere. Oct 2015, Y. Jiang T32781 (Holotype CGMCC 40314, stored in a metabolically inactive state. Ex-type culture CGMCC 40314) .

Description.

Optimal growth at 25 °C, slow at 35 °C on all media.

Colony radius on CMD after 72 h: mycelium covers the plate at 25 °C and 30 °C, 20-22 mm at 35 °C. Colony well-defined, hyaline, sparse aerial mycelia, indistinctly zonate, conidiation begins to develop within 72 h, white at first and turning green after 3-4 d. After 7 d, abundant dark green conidiation around the margin, radially arranged within 2-3 ill-defined concentric zones in the outer half of the colony. Abundant chlamydospores. No diffusing pigment noted, pleasant odor apparent.

Colony radius on PDA after 72 h: mycelium covers the plate at 25 °C, 55-61 mm at 30 °C, 16 mm at 35 °C. Colony similar to CMD but growth a little slower, colony not dark green. Colony well-defined at 35 °C, abundant white thick aerial mycelia. Chlamydospores abundant. No diffusing pigment noted, obvious pleasant odor.

Colony radius on MEA after 72 h: 58-60 mm at 25 °C, 53-55 mm at 30 °C, 11-12 mm at 35 °C. Colony also similar to CMD, but conidiation is yellow green, more abundant around the inoculation plug, uniform distribution all around. No diffusing pigment noted, odor indistinct.

Colony radius on SNA after 72 h: 5-7 mm at 25 °C, 5-6 mm at 30 °C and 35 °C. Colonies well-defined, hyaline, scant aerial mycelia. Slight conidiation dispersedly distributed around the inoculation plug, with white floccose indistinctly zonate tufts or pustules in the margin. No diffusing pigment noted, odor indistinct. Conidiophores consisting of a main axis with side branches mostly at right angles or slightly inclined upward; branches straight or curved, often only longer in basal positions, not re-branching, solitary, paired or in whorls of three. Phialides solitary or commonly in whorls of 2-3, variable in shape, either narrowly lageniform to subulate, particularly when terminal on the main axis, or stout to nearly ampulliform and distinctly swollen, sometimes ampulliform to subglobose, (4.7-)6.0-8.9(-12.1) × (2.5-)2.9-3.4(-4.5) μm (mean =7.7 × 3.3 μm), base (1.5-)1.6-2.6(-3.0) μm (mean = 2.1 μm); phialide length/width ratio (1.2-)1.8-2.9(-3.6) (mean = 2.4) (n = 30). Conidia subglobose to globose, green, smooth, (3.0-)3.2-3.6(-3.9) × (2.8-)3.1-3.4(-3.8) μm (mean = 3.3 × 3.4 μm) with length/width ratio of 1.0-1.1 (mean = 1.1) (n = 30). Abundant chlamydospores, common single, sometimes terminal and intercalary, globose to subglobose, (7.2-)7.8-9.2(-10.1) × (6.1-)7.1-9.0(-9.7) μm (mean = 8.6 × 8.1 μm) (n = 30).

Sexual morph.

Unknown.

Substrate.

Soil.

Distribution.

China, Shandong Provinces.

Additional material examined.

China: Shandong Province, Jinan City , 36°33'45"N, 116°57'05"E, 105 m alt., isolated from corn soils. Aug 2015, Y. Jiang T32450 . China: Shandong Province, Dezhou City , 37°21'07"N, 116°23'40"E, 5 m alt., isolated from soils of corn rhizosphere, Oct 2015, Y. Jiang, T32794 .

Notes.

Trichoderma nigricans can be distinguished from similar species based on growth. After 72 h at 25 °C, T. nigricans mycelium covers the plate on PDA and CMD, T. atroviride grows to 42.8-60.5 mm on PDA, T. obovatum grows to 38-41 mm on CMD, T. uncinatum grows to 55-62 mm on CMD, T. paratroviride to 49-62 mm on CMD and 54-56 mm on PDA ( Samuels et al. 2002; Jaklitsch and Voglmayr 2015; Zheng et al. 2021). In addition, it can be distinguished by its chlamydospores and odor. At 35 °C the growth of T. nigricans is restricted, and no growth occurs in T. paratroviride and T. uncinatum . Chlamydospores are either unobserved or uncommon in T. obovatum , T. uncinatum , and T. paratroviride . Meanwhile, the chlamydospores of T. atroviride and T. nigricans are abundant, and the volume in T. atroviride is usually larger than those in T. nigricans [(5.2-)8.5-12.0(-16.3) vs. (7.2-)7.8-9.2(-10.1) × (6.1-)7.1-9.0(-9.7) μm]. On PDA, the odor of T. paratroviride is pungent; it is indistinct in T. obovatum and T. uncinatum , and pleasant in T. atroviride and T. nigricans .

Figures

Figure 1. Phylogenic tree generated by the maximum likelihood analysis using the concatenated sequences of rpb 2 and tef 1 loci of the genus Trichoderma. Maximum Likelihood Bootstrap values ≥ 70 % (left) and Bayesian posterior probability values ≥ 0.9 (right) are indicated at nodes (MLBP / BIBP). Protocrea farinosa CBS 121551 and P. pallida CBS 299.78 were chosen as the outgroup. Novel species proposed here are indicated in bold.

Figure 2. Cultures and anamorph of T. nigricans strain T 32781 a-d cultures on different media at 25 ° C with a 12 h light and 12 h darkness cycle after 7 d (a on PDA b on MEA c on CMD d on SNA) e Conidiation pustules on PDA after 7 d f conidia g, i-k conidiophores and phialides (g, k on CMD 3 d i on PAD 3 d j on SNA 3 d,) h chlamydospores. Scale bars: 10 μm (f-k).