Tricholoma parafulvum L. Fan, N. Mao & J. J Yang 2025, sp. nov.

Tricholoma parafulvum L. Fan, N. Mao & J. J Yang sp. nov. Figs 2 E, F, 3 E, G Diagnosis. It is distinguished by the combination of the following features: yellowish brown, brown to dark brown pileus, stipe surface covered with brown fibrils, and broadly ellipsoid to ellipsoid basidiospores. It is most similar to Tricholoma fulvum (DC.) Bigeard & H. Guill. but differs in the pileus surface without being radially streaky. Holotype. China • Shanxi Province, Qinshui County, Lishan Mountain, 35°36'5"N, 113°20'29"E, elev. 1600 m, on the ground in broadleaf forest dominated by Quercus sp., 5 October 2023, J. Z. Cao, CF 2300 (BJTC FM 4065), GenBank Acc. No.: ITS = PQ 499537, mtSSU = PQ 499568, tef 1 - α = PQ 509900, rpb 2 = PQ 509910, mcm 7 = PQ 509921. Etymology. Parafulvum (Lat.): referring to the fact that the new species is very similar to Tricholoma fulvum in basidiomatal appearance. Description. Basidiomata small to medium-sized. Pileus 30–66 mm diam., at first hemispherical to convex, later plano-convex to applanate with age, with depression or an umbo at center; surface dry, slightly viscid when wet, yellowish brown (# edd 6 b 8), brown (# d 49 d 76) to dark brown (# b 78877), darker in the center and paler towards the margin, covered with brown (# a 1735 b) to dark brown (# 845546) reflexed fibrillose squamules; margin at first involute, later incurved, cracking with age. Lamellae sinuate, moderately crowded, yellow (# f 3 edd 7) to yellowish brown (# ddb 68 b) when young, turning dark brown (# c 1986 e) with age; lamellulae in 2–3 tiers, concolorous with lamellae. Stipe 42–83 mm long, 5–22 mm diam., cylindrical to clavate, enlarge downwards, dry, white (# f 5 fae 3), yellowish brown (# c 1 a 36 f) to brown (# 9 d 7963), covered with brown (# 7 e 5 c 43) fibrils. Context white (# f 7 f 8 f 7), up to 11 mm. Odor unrecorded. Taste not recorded. Basidiospores [90 / 3 / 3] 4.5–6 × 3.5–4.5 μm, Q = 1.3–1.4, broadly ellipsoid to ellipsoid, smooth, inamyloid, usually containing one large oil droplet. Basidia 23–37 × 4.5–7 μm, clavate, (2 –) 4 - spored, sterigmata up to 5.5 μm long. Cystidioid cells in hymenium absent. Hymenophoral trama regular, composed of cylindrical hyphae, 3–7 μm wide, colorless in water and 5 % KOH. Pileipellis a cutis, composed of cylindrical hyphae, 3–8 µm wide, colorless or yellowish-brown in water and 5 % KOH. Stipitipellis a cutis, composed of parallel hyphae, 2–7 µm wide, colorless in water and 5 % KOH. Clamps absent in all parts of basidioma. Ecology and habitat. Scattered or gregarious on the ground in broadleaf forest dominated by Quercus sp. or Betula sp., currently only known from Shanxi Province, northern China. Additional specimens examined. China • Shanxi Province, Qinshui County, Lishan Mountain, on the ground in broadleaf forest dominated by Quercus sp., 5 October 2023, J. Z. Cao, MS 855 (BJTC FM 4210), GenBank Acc. No.: ITS = PQ 499538, mtSSU = PQ 499569, tef 1 - α = PQ 509901, rpb 2 = PQ 509911, mcm 7 = PQ 509922; ibid., Loufan County, Yundingshan Mountain, on the ground in broadleaf forest dominated by Betula sp., 23 August 2022, N. Mao, MNM 738 (BJTC FM 2500), GenBank Acc. No.: ITS = PQ 499536. Notes. Tricholoma parafulvum belongs to sect. Genuina (Fig. 1). Tricholoma fulvum is morphologically similar and phylogenetically closely related to the new species. They all have brownish caps and ellipsoid basidiospores. However, T. fulvum differs from T. parafulvum by its pileus with radially streaky and relatively larger spores (5.8–7.2 × 4.6–5.1 μm) (Christensen and Heilmann-Clausen 2013). Four species from this section are also found in Shanxi Province, i. e., Tricholoma aurantium, T. ammophilum, T. populinum and T. viscidum. Of them, Tricholoma viscidum is similar to T. parafulvum, both of which are associated with Quercus spp. However, T. viscidum differs from T. parafulvum by its pileus being extremely viscid when wet and relatively larger spores (5–6.5 × 4.5–5.5 μm). The remaining three species are easily distinguished from T. parafulvum, T. ammophilum and T. populinum by their habitats associated with Populus spp., T. aurantium by its stipe surface covered with dense, orange to brownish orange scaly (Heilmann-Clausen et al. 2017).