Tricholoma orienticolossus X. Xu, Y.Y. Cui & Zhu L. Yang, 2020

Xu, Xin, Cui, Yang-Yang & Yang, Zhu L., 2020, Two new species of Tricholoma sect. Genuina (Agaricales) from China, Phytotaxa 443 (2), pp. 155-166 : 159-160

Tricholoma orienticolossus X. Xu, Y.Y. Cui & Zhu L. Yang , sp. nov. Figs. 1–3

MycoBank: MB834640

Etymology:— orienticolossus is proposed because of its similarity to T. colossus .

Type:— CHINA. Sichuan Province: Daofu County, Bamei Town, alt. ca. 3800 m, in forest dominated by Abies , 4 August 2016, Bang Feng 2051 (HKAS 99341).

Basidiomata large to very large. Pileus 13–18 cm in diam., applanate, sometimes slightly depressed at center; surface dry, yellow-brown (6 A2-5 ), brown (4 B3-6 ) to red-brown (6 C4-8 , 6 D6- 8, 6E 5-8), covered with red-brown (6 C4-8 , 6 D6-8) to dark brown (6 E 5- 8, 7E 5-8) fine patches, densely arranged at center ; margin irregularly incurved. Lamellae adnexed to sinuate, dirty white (5 A1-2 ) to brownish (5 B2-4 , 6 A2-3 , 6 B2-4 ), thick (ca. 0.5 mm), moderately crowded ; lamellulae arranged in 3–4 tiers; edges denticulate and dirty white (5 A1-2 ) to brownish (5 B2-4 , 6 A2-3 , 6 B2-4 ) when young, but becoming denticulate to sinuate and distinctly red-brown (6 C4-8 , 6 D6- 8, 6E 5-8) to dark brown (6 E 5- 8, 7E 5- 8) when mature. Stipe 9–15 × 4.5–6.5 cm, robust, clavate, dry, white (3 A1-2 ), dirty white (5 A1-2 ) to brownish (5 B2-4 , 6 A2-3 , 6 B2-4 ), covered with yellow-brown (2 B3-5 ) to red-brown (6 B2-4 , 6 C4-7 , 6 D6-8) squamules, exannulate, but with a ring zone that disappears with age, stuffed and firm in center. Context white, rather firm, unchanging. Taste and odor indistinct .

Lamellar trama 350–400 µm wide, regular, composed of colorless, thin-walled hyphae 3–8 (10) µm in diam, branching, sometimes anastomosing; clamps absent. Subhymenium about 15 µm thick, composed of 3–5 µm wide filamentous hyphal segments. Basidia 60–70 (80) × 9.5–11 µm, clavate, 4-spored, rarely 2-spored, hyaline; sterigmata up to 7 µm long. Basidiospores [40/2/2] (8.0–) 8.5–10 (–10.5) × (6.0–) 6.5–7.5 (–8.0) µm [mean length = 9.1 µm, mean width = 6.8 µm, Q = (1.24–)1.29–1.46(–1.54), Q = 1.35 ± 0.06], ellipsoid, sometimes broadly ellipsoid, inamyloid, colorless, hyaline, thin-walled, smooth; apiculus relatively large. Cheilocystidia 50–120 × 4–8 µm, very common along the lamellar edge, subcylindrical, often septate and slightly capitate, thin-walled, colorless or with yellow to brown granular incrustations and brownish to yellowish vacuolar pigment. Pleurocystidia present, but only common near the lamellar edge, similar to cheilocystidia in form and size. Squamules on pileus a cutis with transition to a trichoderm at regular intervals, composed of loosely and more or less radially arranged, 3–8 µm wide, thin-walled, filamentous hyphae, often with yellow-brown to brown vacuolar pigments; terminal elements subcylindrical to narrowly clavate, 50–80 × 5–9 µm, with round apex. Squamules on stipe surface composed of thin-walled, subcylindrical to narrowly clavate terminal elements (caulocystidia), 60–120 × 3–8 (10) µm, often with fine brown to yellow-brown granular incrustations and brownish yellow vacuolar pigments. Clamps absent in all parts of basidioma.

Habit, habitat, and distribution:—Solitary to scattered on soil in forests dominated by Abies ; fruiting in summer in subalpine forests at altitude of ca. 3800 m.

Additional specimen examined:— CHINA. Sichuan Province: Daofu County, Bamei Town, alt. ca. 3800 m, in forest dominated by Abies , 4 August 2016, Jian-Wei Liu 466 (HKAS 98645).

Figures

FIGURE 1. Phylogenetic analysis of Tricholoma sect. Genuina species inferred from Maximum Likelihood (ML) analysis of ITS sequences. Bootstrap values (ML, ≥ 70%) are shown above or beneath individual branches. Bayesian posterior probabilities (BI, ≥ 0.9) are indicated with thick branches. The two new species are indicated in bold face.

FIGURE 2. Basidiomata of Tricholoma orienticolossus. a and b HKAS 99341 (type), c and d HKAS 98645; Bars = 5 cm a, b Photos by B. Feng; c, d Photos by J.W. Liu.

FIGURE 3. Micro-characteristics of Tricholoma orienticolossus (HKAS 99341, type). a. Pileipellis; b. Basidiospores; c. Caulocystidia and stipitipellis; d. Hymenium near the lamellar edge with pleurocystidia; e. Cheilocystidia. Bars a, c, d and e = 20 μm, b = 10 μm. Drawings by Zhu L. Yang.