Arthrobotrys tachengensis F. Zhang & X.Y. Yang sp. nov.

Index Fungorum number: IF 902261; Mycobank number: MB 902261; Facesoffungi number: FOF 15970;Fig. 1

Etymology – The species name “tachengensis” refers to the name of the sample collection site: Tacheng County, Diqing Tibetan Nationality, Yunnan Province, China.

Holotype – DLUCC179

Saprobic or capture nematodes on soil. Sexual morph: Not observed. Asexual morph: Colonies on PDA white, cottony, growing rapidly, reaching 50 mm diameter after 10 days in the incubator at 26 °C. Mycelium partly superficial, partly immersed, composed of septate, branched, smooth, hyaline. Conidiophores 155–345 µm (x̅=226.9 µm, n = 50) long, 3–6.5 µm (x̅= 4.8 µm, n = 50) wide at the base, gradually tapering upwards to the apex with 2–3.5 µm (x̅=2.7 µm, n=50) wide, erect, septate, hyaline, unbranched or sometimes produce long branches, each branch producing 2–4 short denticles at the apex, each short denticle bearing a single conidium. Conidia 23.5–45.5 × 8.5–17.5 µm (x̅=34.6×13.4 μm, n=50), smooth and hyaline, rounded at the apex and truncated at the base; immature conidia dropshaped, obovate, 1–2 septate, with a larger cell at the apex; mature conidia subfusiform, 2–3-septate (mostly 3-septate, 1 septa at the apex and 1–2 septa at the base), with a larger cell at the middle. Conidia germinate from the small end cells, and the larger cell not germinates. Chlamydospores 6–21.5×5.5–12.5 µm (x̅=12.9×8.7 μm, n=50), cylindrical, ellipsoidal, in chains, hyaline. Capturing nematodes with adhesive networks.

Material examined – China, Yunnan Province, Diqing Tibetan Nationality, Tacheng County, N 27° 34′ 54.02″, E 99° 31′ 18.32″, from freshwater sediment, 11 May 2014, F. Zhang, DLU 89–1 (DLUCC179, holotype).

GenBnak numbers – ITS=pp868283, tef1-α=pp869332, rpb2=pp869333

Notes – The phylogenetic analyses revealed that Arthrobotrys tachengensis is a sister to A. indica but lacking in statistical support (Fig. 2). Although A. tachengensis and A. indica differ only 2.3% (10/426 bp) in ITS sequence, they differ significantly in morphology, with A. tachengensis producing obovate and subfusiform 1–3 septa conidia and A. indica producing obovate 0–2 septa conidia (Zhang & Hyde 2014, Chowdhry & Bahl 1982). Morphologically, A. tachengensis is more similar to A. microscaphoides and A. mangrovispora, there are 4.2% (25/595 bp) and 10.9% (65/598 bp) differences between A. tachengensis and A. microscaphoides and A. mangrovispora on ITS, respectively. In addition, the conidia of A. tachengensis are significantly larger than A. microscaphoides and smaller than A. mangrovispora [A. tachengensis, 23.5–45.5 (34.6)×8.5–17.5 (13.4) µm versus A. microscaphoides, 22.5–45 (27.2)×10–20 (13.9) µm versus A. mangrovispora 25–50 (38.9)×12–24 (17.3) µm] (Zhang & Hyde 2014; Swe et al. 2008; Liu & Lu 1993).

Figure 1 – Arthrobotrys tachengensis (DLUCC179, holotype). a Colony. b Immature conidia. d Mature conidia. e Trapping-device: adhesive networks. f Germinating conidia. g Chlamydospores. c, h Conidiophores. Scale bars: a=1 cm, b, d, e–h=20 µm, c=50 µm

Figure 2 – Maximum likelihood tree based on combined sequences (ITS=627 bp, tef1-α=542 bp and rpb2=822 bp, total 2038 characters, constant sites=900 bp, variable sites=1087 bp, parsimony informative sites=886) from 67 species of Orbiliaceae nematodetrapping fungi (including 59 Arthrobotrys species, 4 Dactylellina species and 4 Drechslerella species). The tree is rooted by Vermispora fusarina (YXJ13-5) and V. leguminacea (CGMCC 6.0291). The best-scoring maximum likelihood tree was performed with a final ML optimization likelihood value of − 6198.356892. Bootstrap support values for maximum likelihood (black) equal or greater than 70% and Bayesian posterior probabilities values (red) equal or greater than 0.90 are indicated above the nodes. The newisolates are in blue, type strains are in bold