Russula spectabilis Manz, F. Hampe & Buyck 2025, sp. nov.

Russula spectabilis Manz, F. Hampe & Buyck, sp. nov. Figs 32, 33, 34 Holotype. Benin. Atakora, Kossoucoingou, co-ord. 10°9.9'N, 1°12.1'E, alt. 500 m, Sudanian woodland, under Isoberlinia tomentosa, on rocky soil, 20. 07. 2021, leg. C. Manz, F. Hampe, G. Abohoumbo, T. C. Bogo, CM-21-154 (holotype B 70 0105435, isotype UNIPAR). Additional material examined. Benin. Atakora, Natitingou, Kota Waterfalls, co-ord. 10°12.7'N, 1°26.8'E, alt. 500 m, Sudanian woodland, under I. tomentosa, on rocky soil, 12. 07. 2021, leg. C. Manz, F. Hampe, N. S. Yorou & G. Abohoumbo, CM-21-116 (paratype, B 70 0105436, UNIPAR). Diagnosis. Basidiomata relatively robust, pileus surface yellow-orange, taste mild, terminal cells of the pileipellis hyphae lanceolate near the pileus margin and narrowly cylindrical near the pileus centre, occurring in savannah woodlands. Differs from Russula aureola Buyck by a lower spore ornamentation. Description. Growth habit: basidiomata solitary. Pileus: medium-sized to large, 80–90 mm in diam., soon expanding plane, centrally depressed; margin even, finely tuberculate-striate up to 10 mm, regularly shaped; cuticle smooth, matt, peelable up to ¾ of the pileus radius, colour butter yellow (4 B 5), near the margin pale orange (5 A 3) or light orange (5 A 4), near the centre, melon (5 A 6) or golden yellow (5 B 7). Lamellae: 6–7 mm wide, 8–9 lamellae present along 1 cm near the pileus margin, narrowly adnate, white to pale cream, furcations frequent at the stipe attachment, anastomoses absent, lamellulae occasionally present; edges entire, concolourous. Stipe: 90–100 × 18–22 mm, cylindrical, smooth to slightly rugose, annulus absent, white; cottony stuffed, cavernate with 2–3 distinct chambers. Context: 6–7 mm thick at half pileus radius, white, unchanging when bruised, brittle, taste mild, odour inconspicuous to pleasant, macrochemical reactions: guaiac after 8–10 seconds (++) on stipe and weakly positive (+) on lamellae surfaces, FeSO 4 weak salmon orange, sulphovanillin negative, KOH negative or slightly discolouring on the pileipellis, phenol negative. Spore print: not observed, probably white or cream. Spores: (6.9 –) 7.4–7.7 – 8.1 (– 8.7) × (6.1 –) 6.4–6.7 – 7 (– 7.4) µm (n = 60), Q = (1.03 –) 1.10–1.15 – 1.20 (– 1.26), subglobose to broadly ellipsoid; ornamentation of moderately distant, dense to very dense, pustules [(5 –) 6–9 (– 12) in a circle of 3 µm diam.], not well defined, by light microscopy up to 0.5 µm high, connected by abundant, short lines [(2 –) 3–6 (– 8) in the circle] forming a complete reticulum, isolated or partially connected elements very rare to absent, occasionally to frequently fused (approx. 1–4 fusions in the circle); suprahilar plage small, inamyloid, without ornamentation. Basidia: (36.5 –) 42–47.5 – 53 (– 58) × (9 –) 10–11 – 12 (– 12.5) µm (n = 40), narrowly to broadly clavate, 4 - spored; basidiola approx. 5–8 µm wide, cylindrical to clavate. Hymenial cystidia: on lamellae sides (60.5 –) 71–83.5 – 95.5 (– 114) × (8.5 –) 9.5–10.5 – 11.5 (– 12.5) µm (n = 40), predominantly lanceolate, sometimes with slight moniliform constrictions, originating in subhymenium and somewhat protruding over basidia, thin-walled, apically obtuse, usually with a 2–13 µm long appendage; heteromorphous contents moderately dense, mostly amorphous, rarely crystalline, mostly located in the upper two-thirds, not reacting to sulphovanillin. Hymenial cystidia near the lamellae edges distinctly shorter and narrower, (38.5 –) 42.5–51 – 60 (– 70) × (6 –) 6.5–7.5 – 9 (– 11) µm (n = 40), lanceolate or rarely cylindrical, apically predominantly mucronate, with broad, 2.5–11 µm long appendages; heteromorphous contents similar to the one in hymenial cystidia on lamellae sides, but less dense. Lamellae edges: sterile, consisting of cystidia and marginal cells. Marginal cells: (23.5 –) 27.5–32.5 – 38 (– 48.5) × (4 –) 4.5–5.5 – 6.5 (– 8) µm (n = 40), narrowly utriform, lageniform or lanceolate, rarely cylindrical with slight constrictions, sometimes with a forked apex, optically empty, thin-walled. Pileipellis: orthochromatic in Cresyl blue, gradually passing to the underlying context, 125–165 µm deep; suprapellis a trichoderm, 30–40 µm deep, composed of erect hyphal terminations; gradually passing to a 95–130 µm deep subpellis of loose, strongly gelatinised, intricate, irregularly orientated, 1.5–4 µm wide hyphae, becoming denser and horizontally arranged near the context. Acid resistant incrustations absent. Hyphal terminations: near the pileus margin composed of 1–4 unbranched cells, thin-walled, frequently covered with a glutinous coating well visible in Congo red, terminal cells (8 –) 11.5–19.5 – 27 (– 40) × (2 –) 2.5–3 – 3.5 (– 4.5) µm (n = 60), predominantly lanceolate or subulate, rarely cylindrical, apically obtuse or acute; subterminal cells usually shorter, 3–6 µm wide, cylindrical or slightly inflated, branched or not. Hyphal terminations near the pileus centre composed of 1–3 unbranched cells, thin-walled, terminal cells shorter, (6.5 –) 9–13 – 17 (– 26) × 2–2.5 – 3 (– 3.5) µm (n = 61), slender, straight, cylindrical; subterminal cells equally long, 2–3.5 µm wide. Pileocystidia: near the pileus margin (15 –) 27–37.5 – 47.5 (– 55.5) × (3 –) 3.5–4.5 – 5.5 (– 7.5) µm (n = 44), one-celled, cylindrical or clavate to subcapitate, rarely lanceolate, flexuous, slightly moniliform, originating in the suprapellis, thin-walled, occasionally with a 2–3 µm long appendage; heteromorphous contents amorphous, not reacting to sulphovanillin. Pileocystidia near the pileus centre similar in size, shape and heteromorphous contents to those near the pileus margin, (24.5 –) 32–40 – 48.5 (– 55) × (4 –) 4.5–5 – 5.5 (– 6.5) µm (n = 40). Context: without cystidioid hyphae, oleiferous hyphae dispersed. Etymology. Reference to the African plant Costus spectabilis (Fenzl) K. Schum., the flower of which is similarly coloured. Distribution and ecology. Only known from the Sudanian woodlands in Atakora in Benin. Notes. Russula aureola, Russula bonii Buyck and Russula singeri R. Heim, are other tropical African species with similar orange pileus colours. Russula aureola has more slender basidiomata and was described from Gilbertiodendron dewevrei forests in the DRC, differing by a high spore ornamentation of 2 µm long spines and a pileipellis with attenuated terminal cells on top of a chain- of barrel-shaped subterminal cells (Buyck 1994). Russula bonii has relatively robust basidiomata with low spore ornamentation. It is known from miombo woodland in Zambia (Buyck 1995). It was placed in subsect. Amoeninae Singer ex Buyck because of the absence of both hymenial cystidia and pileocystidia (Buyck 1995). Russula singeri is a mild species with white spore print which differs by a relatively tough, greying stipe and spores with an amyloid suprahilar plage (Heim 1937, 1938). Russula tenuithrix Buyck has a similar pileipellis structure and low spore ornamentation of up to 0.5 µm height, but differs by its greenish-grey pileus colours (Harkönen et al. 1993). Based on type sequencing, it is not related to R. spectabilis and probably belongs to Russula subgen. Malodorae Buyck & V. Hofstetter. The type sequence of R. tenuithrix will be published in a future study on subgen. Malodorae. Published as part of Manz, Cathrin, Amalfi, Mario, Buyck, Bart, Hampe, Felix, Yorou, Nourou S., Adamčík, Slavomír & Piepenbring, Meike, 2025, Just the tip of the iceberg: uncovering a hyperdiverse clade of African Russula (Basidiomycota, Russulales, Russulaceae) species with signs of evolutionary habitat adaptations, pp. e 140321 in IMA Fungus 16 on page e140321, DOI: 10.3897/imafungus.16.140321