Thelonectria yunnanica Z.Q. Zeng & W.Y. Zhuang, 2013

Zeng, Zhao-Qing & Zhuang, Wen-Ying, 2013, Four new taxa of Ilyonectria and Thelonectria (Nectriaceae) revealed by morphology and combined ITS and - tubulin sequence data, Phytotaxa 85 (1), pp. 15-25 : 19-20

Thelonectria yunnanica Z.Q. Zeng & W.Y. Zhuang , sp. nov.

FIG. 2

MycoBank MB564937

Etymology. The specific epithet refers to the locality of the fungus.

Diagnosis. Differing from Thelonectria discophora in having a thicker perithecial wall, longer cells in the palisade layer, larger asci, wider ascospores, white instead of violet to dark violet colony, and presence of microconidia in culture.

Ascomata perithecial, solitary or gregarious up to 20 in a group, superficial or with base partially immersed in substratum on a minute stroma, subglobose, 350–380 µm high, 450–490 µm diam. (n = 10), not collapsing when dry, red when fresh and brick-red when dry, ostioles blackened with age, slightly papillate, turning dark red in 3% KOH and orange red to orange in lactic acid, surface smooth to slightly roughened. Ascomatal wall 49–71 µm thick, of three layers: outer layer 18–46 µm thick, cells elongated, axis of cells perpendicular to perithecial surface forming a palisade layer, cells 19–24 × 2.4–3.2 µm; middle layer 10–16 µm thick, of texture intricata, hyphae 3–4 µm; inner layer 5.4–10 µm thick, of textura prismatica to textura porrecta, cells rectangular with the long axis parallel to perithecial surface, 8–16 × 4–5.5 µm. Asci cylindrical, 8-spored, with an apical ring, 87–120 × 8.2–9.6 µm. Ascospores ellipsoid, uniseptate, not constricted at septum, slightly yellowish, spinulose, uniseriate with ends overlapping, 13–17 × 6–7.9 µm.

Colony reaching 32 mm in diam. after 7 days on PDA at 25°C under daylight, surface velvety, aerial mycelium white. Conidiophores unbranched to sparsely branched, septate, (28–)30–77(–80) × (1.2–)1.5–3.0(–3.2) µm, arising from agar surface. Microconidia elliptical-fusoid to rod-shaped, straight or slightly curved, rounded at the distal end, hyaline, 0–1-septate, (8–)8.2–16(–16.5) × (3–)3.2–4.5(–4.8) µm. Macroconidia subfusoid to cylindrical, curved, hyaline, (3–)4–7(–9)-septate; (59–)60–93(–93.5)´(5.5–)6–8.8(–9) mm. Chlamydospores absent.

Holotype. CHINA. Yunnan, Baoshan , on bark of an unidentified tree, 15 Oct 2003, W.P. Wu W7122, HMAS 183564 !, ex type culture HMAS 188567 .

Notes. Among the existing species of the genus, Thelonectria yunnanica is most similar to T. discophora in perithecial shape, size and color, structure of the perithecial outer wall, cylindrical asci with an apical ring, and spinulose ascospores. However, T. discophora differs in its thinner perithecial wall (30–50 µm thick) of two layers instead of 3-layered wall, shorter cells in the palisade layer (2–2.5 µm long), smaller asci (72–95 × 7–10 µm), narrower ascospores (12–17 × 5–8 µm), sparse or absence of microconidia, and violet to dark violet colony instead of white ( Brayford et al. 2004, Guu et al. 2007, Hirooka and Kobayashi 2007).

It is also similar to T. trachosa and T. viridispora in the 3-layered perithecial wall. Thelonectria trachosa differs in having larger ascospores (17.5–20.5 × 6–9 µm vs. 13–17 × 6–7.9 µm) and the absence of microconidia ( Brayford et al. 2004) . Thelonectria viridispora differs in having smaller perithecia (300–375 µm vs. 450–490 µm in diam.) and the absence of microconidia ( Brayford et al. 2004) .

Figures

FIGURE 2. Thelonectria yunnanica (holotype). A. Median section of an ascoma; B. Structure of lateral perithecial wall; C. Colony on PDA; D−F. Macroconidia; G, H. Conidiophores and microconidia; I. Asci with ascospores.