Tricholoma fumeobrunneum L. Fan, N. Mao & J. J Yang sp. nov.

Figs 2 C, D, 3 B, D

Diagnosis.

It is distinguished by the combination of the following features: pale gray to grayish-brown pileus, smooth stipe, and broadly ellipsoid to ellipsoid basidiospores. It is most similar to T. sinopardinum Zhu L. Yang, X. X. Ding, G. Kost & Rexer but differs by the smaller basidiospores (6.5–8.5 × 5–6.5 μm).

Holotype.

China • Shanxi Province, Lingchuan County, Lishan Mountain, 35°36'6"N, 113°20'32"E, elev. 1185 m, on the ground in broadleaf forest dominated by Quercus sp., 28 August 2023, Y. Li, MS 492 (BJTC FM 3436), GenBank Acc. No.: ITS = PQ 499553, mtSSU = PQ 499565, tef 1 - α = PQ 509897, rpb 2 = PQ 509908, mcm 7 = PQ 509918.

Etymology.

fumeobrunneum (Lat.): referring to the cap color of the basidiomata.

Description.

Basidiomata small to medium-sized. Pileus 25–77 mm diam., at first convex, later broadly convex, plano-convex to applanate with age, with an umbo at center; surface dry, pale gray (# cac 7 c 0) to grayish-brown (# 9 d 8166), center darker to dark gray (# aaa 9 a 3) to grayish black (# 6 b 6157) when mature, covered with dark gray (# 8 e 8 c 95) reflexed fibrillose squamules; margin at first involute, later incurved, cracking with age. Lamellae sinuate, moderately crowded, dirty white (# f 9 f 8 e 9) to pale yellow (# f 1 eeca), turning yellowish brown (# e 7 dbb 2) to brown (# d 6 bb 9 c) with age; lamellulae in 2–4 tiers, concolorous with lamellae. Stipe 50–76 mm long, 7–15 mm diam., cylindrical to clavate, enlarged downwards, dry, white (# f 6 f 7 f 7), pale yellow (# f 1 ffe 3) to yellowish brown (# ab 9065), smooth. Context white (# f 9 f 9 f 9), up to 3.3 mm. Odor unrecorded. Taste not recorded.

Basidiospores [120 / 3 / 4] 6.5–8.5 × 5–6.5 μm, Q = 1.3–1.6, broadly ellipsoid to ellipsoid, smooth, inamyloid, usually containing one large oil droplet. Basidia 34–46 × 6–9 μm, clavate, (2 –) 4 - spored, sterigmata up to 6 μm long. Cystidioid cells in hymenium absent. Hymenophoral trama regular, composed of cylindrical hyphae, 3–12 μm wide, colorless in water and 5 % KOH. Pileipellis a cutis, composed of cylindrical hyphae, 3–10 µm wide, colorless or yellowish-brown in water and 5 % KOH. Stipitipellis a cutis, composed of parallel hyphae, 1.5–6 µm wide, colorless in water and 5 % KOH. Clamps common in all tissues.

Ecology and habitat.

Scattered or gregarious on the ground in broadleaf forest dominated by Quercus sp., currently only known from Shanxi Province, northern China.

Other specimens examined.

China • Shanxi Province, Lingchuan County, Lishan Mountain, on the ground in broadleaf forest dominated by Quercus sp., 5 September 2023, N. Mao, MNM 891 (BJTC FM 3571), GenBank Acc. No.: ITS = PQ 499554; ibid., Lingchuan County, Lishan Mountain, 35°36'6"N, 113°20'32"E, elev. 1190 m, on the ground in a broadleaf forest dominated by Quercus sp., 28 August 2023 H. M. Ji, MS 492 (BJTC FM 3445), GenBank Acc. No.: ITS = PQ 499552, mtSSU = PQ 499566, tef 1 - α = PQ 509898, rpb 2 = PQ 509909, mcm 7 = PQ 509919; ibid., 5 September 2023, N. Mao, MNM 894 (BJTC FM 3574), GenBank Acc. No.: ITS = PQ 499555, mtSSU = PQ 499567, tef 1 - α = PQ 509899, mcm 7 = PQ 509920.

Notes.

Tricholoma fumeobrunneum belongs to the sect. Pardinicutis (Fig. 1). Tricholoma fumeobrunneum was phylogenetically sister to T. sinopardinum, a species found in Xizang Autonomous, southwestern China. However, T. sinopardinum differs from the new species by its stipe covered with brownish, brown to dark brown fibrillose to reflexed squamules and larger basidiospores (8.5–10.5 × 6.5–7.5 μm) (Yang et al. 2017). Tricholoma highlandense Zhu L. Yang, X. X. Ding, G. Kost & Rexer, another species from China in this section, is easily distinguished from T. fumeobrunneum by its pileus without a tinge of gray and occurrence in red acid soil (Yang et al. 2017).