Brownish yellow false truffle (Truncocolumella pseudocolumella), new species for science from China

NEWS - Brownish yellow false truffle (Truncocolumella pseudocolumella L. Li, S.H. Li & Y. Wang, sp. nov.) established as a new species for science based on specimens found during a survey of hypogeous fungi in the Hengduan Mountains, Sichuan Province, southwest China.

Truncocolumella Zeller 1939 a small genus of false truffles with the type species Truncocolumella citrina Zeller 1939. To date only T. citrina and Truncocolumella occidentalis Malençon & Zeller 1940 have been recognized. T. citrina is a common ectomycorrhizal species found in coniferous forests in North America. However, T. occidentalis is rare and has only been found in Canada.

A single specimen was found in the Yala Mountains in western Sichuan Province, China. Two additional collections were later found in the same area. Western Sichuan Province, part of the Hengduan Mountains, is one of the most biodiverse regions in the world.

T. pseudocolumella differs from other species in the genus Truncocolumella in that the basidiomata are not columnar. The epithet pseudocolumella refers to the absence of a columella. The new species occurs in soil associations with Quercus guyavaefolia and Pinus sp.

Furthermore, the basidiomata of T. citrina are 2–4 cm in diameter, comparable to those of T. pseudocolumella (1.5–3 cm), but two to three times larger than those of T. occidentalis. The surface of the basidiomata of T. citrina is citrine yellow, T. pseudocolumella is yellow-brown and T. occidentalis is white, although the color of T. occidentalis is uncertain because it was preserved in alcohol.

Microscopically, T. citrina has ellipsoid spores measuring 6–10 × 3.5–5.0 μm, with individual spores appearing nearly hyaline. Similarly, T. pseudocolumella has ellipsoid spores measuring 7.5–10.0 × 4.0–5.0 μm that are also nearly hyaline, indicating a close resemblance between the two.

T. citrina spores are markedly shorter, more oblong and more irregular in shape than T. occidentalis spores whose bodies are long elliptical or sometimes subcylindrical.

DESCRIPTION

Basidiomata irregularly depressed-globose to pyriform, with a yellowish-tawny (4C8) rhizomorphic base, 1.5–3.0 cm in diameter, the surface typically smooth and dry in appearance, light yellowish-tawny (4C5) with yellowish-brown (4C8) rhizomorphs, colour unchanged on bruising or exposure, elastic, very mature basidiomata deliquesce like Rhizopogon. Odour light and pleasant.

Peridium 102–160 μm thick, not separating or evanescent from the gleba at maturity, composed of two layers: outer layer 52–73 μm thick, reddish-tawny (7D7) interwoven hyphae of 1–1.5 μm diameter. The inner layer 40–86 µm thick, consisting of brownish-hyaline nearly parallel interwoven hyphae of 0.5–1.5 μm diameter. The boundary between the inner and outer layers gradually transitioning, with the changes in hyphae arrangement direction and hyphae colour.

The clamp connection clearly visible, dry peridium becoming black (4F4) when encountering 5% KOH. Gleba pale white when immature, light brown to tawny at maturity, unchanging on bruising or exposure, cavities relatively small, spongy, lacking obvious columnar or dendroid radiating columella. Trama (56.0–) 62.5–85.0 μm, composed of hyaline almost parallel hyphae.

Hymenium present on cavities surface. Basidia narrowly clavate, (15.0–) 17.2–19.5 (–22.4) × 3.5–6.5 (–7.0) μm, 2-4-spored. Sterigmata 2–3 μm. Basidiospore ellipsoid, smooth, 7.5–10.0 (–11.0) × 4.0–5.0 (–5.6) μm, grey to brownish (7D5) in mass, as seen individually, almost hyaline, typically 1–2 guttulate, infrequently 3-guttulate, changing to blue in lactophenol cotton blue, not obvious discolouration in Melzer's reagent.

Original research

Li L, Wan S, Wang Y, Thongklang N, Luo Z, Li S (2024). A new species of the genus Truncocolumella (Basidiomycota, Boletales) found in the Hengduan Mountains of China. Biodiversity Data Journal 12: e128970, DOI:10.3897/BDJ.12.e128970

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