Tuber mongolicum T. Bau & F. Guo, 2023

Guo, Fang & Bau, Tolgor, 2023, A new species of Tuber (Tuberaceae, Pezizales) from Inner Mongolia, China, Phytotaxa 592 (1), pp. 39-48 : 43-45

Tuber mongolicum T. Bau & F. Guo sp.nov. ( Figure 2–5 )

MycoBank number:—846829

Diagnosis:— Tuber mongolicum differs from related species by its pseudoparenchymatous peridum, ellipsoid ascospores and 1–5 spored asci.

Etymology:—‘mongolicum’ refers to its occurrence in Inner Mongolia Autonomous Region, China.

Types:— CHINA, Inner Mongolia Autonomous Region, Tongliao Daqinggou National Nature Reserve , in soil under Populus sp. , 42°47′N, 122°10′E, 214 m, 23 Aug. 2022, Fang Guo, Tolgor Bau, HMJAU65125 (holotypus!). Same location; Fang Guo, Tolgor Bau HMJAU65126 (paratypus!) .

Description:—Ascomata are spherical to irregular spherical, 0.8–1.5 cm in diameter, with depressions. The surface is yellowish-green (30B7), olive-brown (4D7) to yellowish brown (5D8) when fresh, with small protrusions at the concave part of the fruiting body. Gleba is yellow-brown with white veins that have a sparse radial distribution from the base, and starch-like aroma ( Figs 2–3 ).

Peridum is 349–506 µm, thick, with two layers: the outer layer is yellow-brown, and 71–174 μm thick, the inner layer is a clear shade, 205–418 μm thick, and composed of sub-globose pseudoparenchymatous cells of 15–33 × 9–20 µm wide ( Figs 4a , 5c ). Asci are usually 1–4-spored, but occasionally 5-spored. Asci are sub-globose to ellipsoid, thin-walled, and short or nearly sessile, measuring 56–91 × 46–68 µm ( Figs. 4 b-c. 5b). Ascospores are oblong-ellipsoid, ellipsoid to broadly ellipsoid, yellow-brown at maturity, and reticulate. In 1-spored asci 38–50 × 30–40 µm, Q=1.1–1.28, in 2- spored asci 33–44 × 25–37 µm, Q=1.1–1.4, in 3-spored asci 28–40 × 22–28 µm, Q=1.15–1.43, in 4-spored asci 25–35 × 20–29 µm, Q=1.15–1.37, in 5-spored asci 26–31 × 22–25 µm, Q=1.1–1.24, spike ornamentation 2.92–5.06 µm length, and mostly 3–6 meshes across the spore width ( Figs 4 b-c, 5b).

Habitat: Hypogeous, in soil under Populus sp. ; ascoma occurring in autumn.

Distribution: Only within Inner Mongolia Autonomous Region, Northern China.

Figures

FIGURE 4. Tuber mongolicum (HMJAU65125, holotypus!) a. Peridium; b-c. Asci and Ascospores; d. Ascospore observed under SEM. Bars: a=100µm; b-d=10µm. Photos by author.

FIGURE 5. Tuber mongolicum (HMJAU65125, holotypus!) a. Ascomata and vertical section; b. Asci and Ascospore; c. Peridium. Bars: a=1cm; b=10µm; c=100µm. Drawings by author.

FIGURE 2–3. Ascomata of Tuber mongolicum (2. HMJAU65125; 3. HMJAU65126) on grassland and vertical section of Tuber mongolicum. Bars: a, b=1 cm, Photos by author.