Hygrophorus parvirussula H.Y. Huang & L.P. Tang, 2018

Huang, Hong-Yan, Yang, Shu-Da, Zeng, Nian-Kai, Zhang, Guo-Li, Hu, Yu & Tang, Li-Ping, 2018, Hygrophorus parvirussula sp. nov., a new edible mushroom from southwestern China, Phytotaxa 373 (2), pp. 139-146 : 142-143

Hygrophorus parvirussula H.Y. Huang & L.P. Tang , sp. nov. ( Figs. 2–4 )

MycoBank: MB 825107.

Etymology:—Latin “parvi” meaning small, “russula ” from the name of H. russula , referring to the new species similar to H. russula , but having smaller basidiomata than the later.

Diagnosis:— Hygrophorus parvirussula is different from European H. russula in the smaller basidiomata, slightly larger basidiospores, the presence of cheilocystidia and pleurocystidia, and a stipitipellis composed of hyphae arranged in parallel. This new Chinese species usually grows solitary in broad-leaved mixed forests of the subalpine belt of southwestern China.

Holotype:— CHINA. Yunnan Province: Wuding Prefecture, Gaoqiao Town , 102°5′11”E, 25°39′14”N, elev. 2500 m, 23 August 2016, MHKMU N.K. Zeng 2878.

Gene sequences ex-holotype:—MH160770 (ITS); MH160774 (LSU).

Description:— Basidiomata solitary to sparsely scattered on soil, small to medium-sized, fleshy, rather fragile. Pileus 6–8 cm diam., hemispheric or convex in youth, applanate or shallowly depressed at maturity; surface dry, slimy when wet, pale flesh pink to reddish purple, covered with reddish brown fibrillose squamules at center; margin incurved when young, slightly even in age; context whitish to pinkish white, thick on disc 0.4–0.5 cm, thin on margin. Lamellae adnate to slightly decurrent, close to crowded (10–20/cm), 4–9 mm deep, pink to reddish purple, rather fragile, short gills or lamellulae numerous and narrowed. Stipe 6.5–7.5 cm long, 0.5–1.5 cm thick, central to slightly eccentric, cylindrical, equal or slightly tapering upward, slightly curved, surface pale flesh pink to reddish purple, covered with reddish brown fine fibrils or scattered scales, more or less concolorous with the pileus; flesh initially firm, becoming soft with age, whitish to pinkish white, becoming pink on exposure; basal mycelium white. Odor not distinctive or very weak. Taste not recorded.

Basidiospores [80/3/3] 6.9–9.0 × 4.6–6.6 (–6.9) μm, Q= (1.13–) 1.14–1.8 (–1.83), Q m = 1.48 ± 0.23, long ellipsoid to ellipsoid, smooth under the light microscope, but with bacillate ornamentation under SEM, thin-walled, hyaline, with distinct hilar appendix, yellowish in Melzer’s reagent. Basidia 30–55 × 5–10 μm, 2- and 4-spored, clavate, thin-walled; sterigmata 4–8 μm in length. Cheilocystidia 30–60 × 3–7 μm, rare, scattered, subfusiform or fusiform, narrowly clavate, spathulate, subcylindric, flexuous, thin-walled, colorless. Pleurocystidia 30–55 × 3–6 μm, abundant, scattered, narrowly clavate, spathulate, subcylindric, flexuous, thin-walled, hyaline. Lamellar trama divergent, composed of short and long hyphae, short hyphae 5–12 × 5–6 μm, next to hymenium, globose, subglobose, broadly ellipsoid, pear-shaped or irregularly shaped, colorless and hyaline; long hyphae 24–27 × 3–8 μm, long ellipsoid, clavate or irregularly shaped, colorless and hyaline. Pileipellis an ixotrichoderm, consisting of narrow hyphae (3–5 μm diam.) in gluten, loosely interwoven, branched or non-branched, thin-walled. Pileal trama made up of hyphae 8–18 μm diam., thin-walled. Stipitipellis composed of hyphae 5–8 μm diam., arranged in parallel, thin-walled. Stipititrama made up of hyphae 5–18 μm diam., arranged in parallel, thin-walled. Mycelial hyphae 2–4 μm broad, smooth under the light microscope and SEM. Clamp connections present in all tissues.

Substrate and habitat:—Solitary or scattered in subtropical forests, elev. more than 2000 m; in the summer (July– August).

Known distribution:—The subtropical subalpine belt of Yunnan Province and Sichuan Province, southwestern China.

Additional materials examined:— CHINA. Sichuan Province: Danba Prefecture, Donggu Town, 24 July 2007, HKAS 53605 (Z.W. Ge 1519) [GenBank Acc. No.: MH160768 ( ITS); MH160772 ( LSU)]. Yunnan Province: Jianchuan Prefecture , Shibao mountain , elev. 2500 m, 18 August 2014, MHKMU L.P. Tang 1691 [GenBank Acc. No.: MH160769 ( ITS); MH160773 ( LSU)] ; Wuding Prefecture, Gaoqiao Town , 102°5′11”E, 25°39′14”N, elev. 2500 m, 23 August 2016, MHKMU S.D. Yang 434 [GenBank Acc. No.: MH160771 ( ITS); MH160775 ( LSU)] .

Figures

FIGURE 2. Basidiomata of Hygrophorus parvirussula. a, d from MHKMU N.K. Zeng 2878; b, e from MHKMU L.P. Tang 1691; c, f from MHKMU S.D. Yang 434 (a, d photos by N.K. Zeng; b, e photos by L.P. Tang; c, f photos by S.D. Yang). Bars =1 cm.

FIGURE 3. Microscopic features of Hygrophorus parvirussula. (MHKMU N.K. Zeng 2878). a. Pileipellis. b. Basidia, pleurocystidia and lamellar trama. c. Stipitipellis. Bars = 10 μm. Drawings by H.Y. Huang.

FIGURE 4. Basidiospores of Hygrophorus parvirussula. (MHKMU N.K. Zeng 2878). a. Basidiospores under light microscope. b, c. Basidiospores under SEM. Bars: a = 10 μm, b, c =1 μm. Photos by H.Y. Huang.