Russula atrochermesina Y. L. Chen & J. F. Liang, 2024

Chen, Yanliu, Chen, Bin, Liang, Ruoxi, Wang, Shengkun, An, Mengya, Zhang, Jinhua, Liang, Jingying, Wang, Yaxin, Gao, Xuelian & Liang, Junfeng, 2024, Four new species of Russula subsect. Cyanoxanthinae from China (Russulales, Russulaceae), MycoKeys 107, pp. 21-50 : 21-50

Russula atrochermesina Y. L. Chen & J. F. Liang , sp. nov.

Figs 2 A – C , 3 A – D , 4 , 5

Diagnosis.

Russula atrochermesina can be distinguished by its violet pileus with tuberculate-striate margin, distant lamellae that stain greyish-yellow when bruised, wide hymenial cystidia on lamellae edges, cystidia content negative reaction in sulphovanillin, branched subterminal cells in pileipellis.

Holotype.

China, Yunnan Province, Chuxiong Yi Autonomous Prefecture, Lufeng City, Tuoan Township , 25 ° 14 ' 35 " N, 101 ° 46 ' 23 " E, alt. 2250 m, 7 Sep 2023, Y. L. Chen ( RITF 6878 ).

Etymology.

‘ atrochermesina ’ refers to the dark purple colour of pileus.

Description.

Basidiomata medium to large-sized; pileus 75–115 mm in diameter, initially hemispherical when young, convex to applanate when mature, margin tuberculate-striate, not cracked; surface dry, glabrous, peeling readily, violet white (16 A 2) to pale violet (16 A 3), dark violet (16 F 6) in the centre. Lamellae adnate, 5–8 per cm near pileus margin, cream, staining greyish-yellow (2 B 5) when bruised; lamellulae present and irregular in length; furcations frequently present near the stipe; edge entire and concolorous. Stipe 80–170 × 25–40 mm, cylindrical to subcylindrical, white (1 A 1), often with yellowish-white (1 A 2) tinge, solid. Context white (1 A 1), unchanging when bruised, compact, 5 mm thick in half of the pileus radius; taste mild; odour inconspicuous. Spore print not observed.

Basidiospores (6.3 –) 6.7–7.2 – 7.6 (– 8.7) × (5.3 –) 5.8–6.2 – 6.5 (– 7.4) µm, Q = (1.05 –) 1.11–1.15 – 1.20 (– 1.25), subglobose to broadly ellipsoid, hyaline in 5 % KOH; ornamentation of small to medium, dense (5–9 in a 3 μm diam. circle) amyloid warts, less than 0.6 μm high, mostly isolated or fused in pairs, occasionally fused by short lines; suprahilar plage inamyloid. Basidia (33.0 –) 37.0–43.0 – 48.5 (– 52.0) × (9.0 –) 10.0–11.5 – 12.5 (– 14.0) µm, clavate, 2 - to 4 - spored, thin-walled; basidiola clavate, ca. 8.0–12.5 µm wide. Hymenial cystidia on lamellae sides moderately numerous, (52.5 –) 55.0–60.5 – 65.5 (– 69.5) × (7.0 –) 8.0–8.5 – 9.5 (– 10.0) µm, fusiform, apically acute, usually with an appendage, thin-walled; contents heteromorphous, yellow in sulphovanillin. Hymenial cystidia on lamellae edges longer and wider than those on lamellae sides, (54.5 –) 58.0–65.0 – 71.5 (– 75.5) × (8.0 –) 9.0–10.5 – 11.5 (– 13.0) µm, fusiform, apically mostly acute, usually with an appendage, thin-walled; contents crystalline, yellow in sulphovanillin. Marginal cells undifferentiated. Pileipellis hyphae of all tissues metachromatic in cresyl blue, sharply delimited from the underlying context, two-layered, gelatinised; suprapellis 260–400 µm deep, composed of densely arranged and erect hyphal terminations; subpellis 150–200 µm deep, composed of horizontally orientated and 2–9 μm wide hyphae. Hyphal terminations near the pileus margin branched, thin-walled; terminal cells (9.0 –) 13.5–18.0 – 22.5 (– 27.5) × (2.5 –) 3.5–4.0 – 5.0 µm, mainly clavate, occasionally cylindrical, apically mostly obtuse; subterminal cells usually shorter, ca. 3.0–5.5 µm wide, branched. Hyphal terminations near the pileus centre slightly narrower than those near the pileus margin; terminal cells (10.0 –) 13.5–17.5 – 21.5 (– 26.5) × (2.5 –) 3.0–3.5 – 4.0 (– 5.0) µm, cylindrical, slightly attenuated. Pileocystidia near the pileus margin always 1 - celled, (22.5 –) 28.5–36.0 – 44.0 (– 50.0) × (4.0 –) 4.5–5.0 – 6.0 (– 6.5) µm, dispersed, clavate, occasionally fusiform, apically usually obtuse, sometimes with a round or elliptical appendage, thin-walled; contents crystalline, no reaction in sulphovanillin. Pileocystidia near the pileus centre slightly narrower than those near the pileus margin, (30.0 –) 32.0–38.0 – 44.0 (– 51.5) × (3.5 –) 4.0–4.5 – 5.0 (– 5.5) µm.

Habitat.

On the ground under mixed forests dominated by Castanopsis sclerophylla and Pinus yunnanensis .

Known distribution.

South-western China (Yunnan Province).

Additional specimens examined.

China, Yunnan Province, Chuxiong Yi Autonomous Prefecture, Lufeng City, Tuoan Township , 25 ° 14 ' 34 " N, 101 ° 45 ' 39 " E, alt. 2300 m, 28 Jul 2022, X. L. Gao ( RITF 6460 ) .

Notes.

Phylogenetic analyses showed that R. atrochermesina is related to R. pallidirosea , R. purpureorosea and R. purpureoviridis Khamsuntorn, Lueangjaroenkit, Sommai & Pinruan. However , R. pallidirosea from American Samoa has a pallid to pinkish pileus and smaller hymenial cystidia on the lamellae edges (40.0–55.0 × 5.0–7.0 µm) and is associated with tropical trees ( Kropp 2016). Russula purpureorosea differs in the following set of characters: pale pinkish-purple pileus, lamellae furcations absence, narrower hymenial cystidia on lamellae edges (54.0–60.0 – 95.0 × 7.0–8.5 – 10.0 µm) and unbranched hyphal terminations in the pileipellis ( Song 2022). Russula purpureoviridis , originally described from Thailand, differs in a greyish-green pileus, narrower hymenial cystidia on lamellae edges (45.0–77.5 × 7.5–10.0 µm), constricted terminal cells in the pileipellis and larger pileocystidia (52.5–87.5 × 5.0–8.5 µm) ( Crous et al. 2022). The morphology of R. atrochermesina is similar to R. fusiformata . However, R. fusiformata lacks lamellulae and furcations and has narrower hymenial cystidia on lamellae edges (35.5–52.0 – 78.0 × 5.0–9.0 – 11.0 µm) and shorter and wider terminal cells near the pileal centre (5.5–14.0 × 3.0–8.0 µm) ( Song 2022).

Figures

Figure 2. SEM photos of basidiospores of the four new species A – C Russula atrochermesina (RITF 6878, holotype) D – F Russula lavandula (RITF 6329) G – I Russula lilaceofusca (RITF 6330, holotype) J – L Russula perviridis (RITF 3131, holotype). Scale bars: 20 µm (G); 10 µm (A, B, D, E, H, J, K); 5 µm (C, F, I, L).

Figure 3. Fruiting bodies photos of four new species A – D Russula atrochermesina (A-C-RITF 6878, holotype, D-RITF 6460) E – I Russula lavandula (E-F-RITF 6329, G-H-RITF 6340, I-RITF 3282, holotype) J – L Russula lilaceofusca (J-K-RITF 6330, holotype, L-RITF 2631) M – R Russula perviridis (M-N-RITF 3131, holotype, O-P-RITF 6982, Q-R-RITF 6983). Scale bars: 40 mm (A, B, D – G, I, J, M – O); 5 mm (C, L); 20 mm (H, K, P, Q, R).

Figure 4. Russula atrochermesina (RITF 6878, holotype) A basidia B basidiola C hymenial cystidia on lamellae sides D hymenial cystidia on lamellae edges. Scale bar: 10 µm.

Figure 5. Russula atrochermesina (RITF 6878, holotype) A hyphal terminations near the pileus margin B hyphal terminations near the pileus centre C pileocystidia near the pileus margin D pileocystidia near the pileus centre. Scale bar: 10 µm.