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

Tricholoma flavoviride L. Fan, N. Mao & J. J Yang sp. nov. Figs 2 A, B, 3 A, C Diagnosis. It is distinguished by the combination of the following features: greenish-yellow to yellowish-brown pileus, stipe surface with brownish fibrils, or reflexed squamules. It is most similar to T. citrinum Y. Y. Cui & Zhu L. Yang but differs by habitat associated with broadleaf forest. Holotype. China • Shanxi Province, Pu County, Wulu Mountain, 36°33'34"N, 111°12'40"E, elev. 1510 m, on the ground in broadleaf forest dominated by Quercus sp., 28 September 2023, J. Z Cao, MS 808 (BJTC FM 4164), GenBank Acc. No.: ITS = PQ 499560, mtSSU = PQ 499564, rpb 2 = PQ 509907, mcm 7 = PQ 509917. Etymology. flavoviride (Lat.): referring to the color of the basidiomata. Description. Basidiomata small to medium-sized. Pileus 20–55 mm diam., at first hemispherical to convex, later plano-convex to applanate with age, with an umbo at center; surface dry, slightly viscid when wet, greenish-yellow (# dbd 252) to yellowish-brown (# c 2 a 677), center darker to dark brown (# 7 a 614 d) when mature, covered with brown (# b 49976) squamules; margin incurved or not. Lamellae sinuate, crowded, greenish-yellow (# b 4 ae 6 c) to yellowish-brown (# d 9 c 45 b); lamellulae in 2–4 tiers, concolorous with lamellae. Stipe 32–70 mm long, 12–17 mm diam., cylindrical, equal or enlarge downwards, dry, white (# f 9 f 9 f 8) at apex, pale yellow (# e 7 e 1 a 5) to yellowish brown (# d 7 cb 67) below, covered with brownish (# 9 c 8 c 58) fibrils or reflexed squamules. Context white (# ffffff). Odor unrecorded. Taste not recorded. Basidiospores [90 / 3 / 3] 5–6.5 × 3.5–5 μm, Q = 1.2–1.6, ellipsoid, smooth, inamyloid, usually containing one large oil droplet. Basidia 24–37 × 5.5–7.5 μm, clavate, (2 –) 4 - spored, sterigmata up to 4.5 μm long. Cystidioid cells in hymenium absent. Hymenophoral trama regular, composed of cylindrical hyphae, 4–10 μm wide, colorless in water and 5 % KOH. Pileipellis a cutis, composed of cylindrical hyphae, 4–10 µm wide, colorless or yellowish in water and 5 % KOH. Stipitipellis a cutis, composed of parallel hyphae, 2–6 µm wide, colorless in water and 5 % KOH. Clamps absent 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. Additional specimens examined. China • Shanxi Province, Pu County, Wulu Mountain, on the ground in broadleaf forest dominated by Quercus sp., 28 September 2023, J. Z Cao, CF 2196 (BJTC FM 3966), GenBank Acc. No.: ITS = PQ 499559, mtSSU = PQ 499563, rpb 2 = PQ 509906, mcm 7 = PQ 509916; ibid., Qinshui County, Lishan Mountain, on the ground in broadleaf forest dominated by Quercus sp., 7 September 2023, N. Mao, MNM 829 (BJTC FM 3512), GenBank Acc. No.: ITS = PQ 499561, mtSSU = PQ 499562, rpb 2 = PQ 509905, mcm 7 = PQ 509915. Notes. Tricholoma flavoviride belongs to the sect. Tricholoma (Fig. 1). Tricholoma citrinum, a species recently described from Yunnan Province of southwestern China (Cui et al. 2022), is morphologically and phylogenetically closely related to the new species. Both species have brownish-yellow pileus and ellipsoid basidiospores. However, T. citrinum is distinguished from T. flavoviride by its relatively paler pileus, stipe sometimes smooth, and habitat association with pine forests. Morphologically, T. flavoviride is also easily confused with T. equestre (L.) P. Kumm., and T. frondosae Kalamees & Shchukin. Tricholoma equestre is distinguished from T. flavoviride by its larger basidiospores (6.5–9 × 4–5.5 μm) and habitat associated with pine forests; T. frondosae by its paler pileus and larger basidiospores (7–8.5 × 4–5 μm) (Christensen and Heilmann-Clausen 2013; Reschke et al. 2018; Cui et al. 2022).