Pluteus keselakii Ševčíková, P., 2020

Ševčíková, Hana, Moreau, Pierre-Arthur & Borovička, Jan, 2020, Pluteus keselakii (Pluteaceae, Agaricales), a new species in section Celluloderma, Phytotaxa 432 (2), pp. 181-189 : 184-186

Pluteus keselakii Ševčíková, P. -A. Moreau & Borovička sp. nov. Figs. 2 , 3

MycoBank: MB832255

Etymology:— “ keselakii ” honours the collector of the holotype, Pavol Kešeľák.

Diagnosis:—Differs from Pluteus floccipes by the mostly (narrowly) utriform or fusiform pleurocystidia with obtuse apex, shorter caulocystidia which are also more variable in shape, and by distinct ITS and EF1-α sequences.

Holotype:— Slovakia. Ondavská vrchovina, Detrík , Domaša-Dobrá, Suchý potok valley, 230 m a.s.l., on soil under Corylus avellana , 29 August 2008, P. Kešeľák, BRNM 817402 ; GenBank/ EMBL: MN250223 ( ITS rDNA and LSU); LR699073 ( EF1 -α).

Description:— Pileus 15–27 mm broad, convex or hemispherical when young, later plano-convex; surface slightly radially rugose-venose at centre, slightly radially rugose or smooth at margin, not striate or translucently striate up to half the radius, with crenulate or uplifted margin in some cases, glabrous or slightly minutely pruinose, shiny, opaque when dried, not hygrophanous, dark ochraceous brown to almost blackish when young, becoming light chestnut brown from margin when moist, brown (7.5YR 3/4) or dark reddish brown (5YR 3/2–3/4) to reddish brown (5YR 4/3–4/4), very dark brown at centre (10YR 2/2, 3/3–3/4), consistently fading all over to light greyish brown when drying. Lamellae moderately distant, L = 30–48, l = 1–2(3), free, ventricose to broadly ventricose, up to 4.5 mm broad, white when young, becoming pinkish white (5YR 8/2), with 1–3 lamellulae, lamella edge brown to grey-brown; in some lamellae brownish only near pileus margin and whitish towards stipe. Stipe 20–45 × 2–3 mm, cylindrical, with slightly broadened base, innately longitudinally fibrillose or striate-twisted, white (10YR 8/1) to hyaline grey, squamulose to densely covered with distinct brown floccules, more conspicuous (more closely covered) in upper part, with white tomentum at the base of some basidiocarps. Context white to whitish. Smell indistinct. Taste not recorded. Basal mycelium opaline, sparse. Spore print pink.

Basidiospores (5.5) 6–8 (9) × (5) 6–7 (8) μm, avl × avw = 7.5 × 6.8 μm, Q = 1.00–1.40, avQ = 1.11, subglobose, rarely globose, broadly ellipsoid or ellipsoid. Basidia (18) 20–35 × 8–10 (11) μm, tetrasterigmate, clavate to subfusiform or (narrowly) utriform, hyaline. Pleurocystidia scattered, scarce to moderately abundant, (42) 48–74 (80) × 17–30 μm, narrowly utriform to utriform, fusiform with obtuse apex or spathulate, rarely clavate, utriform with median constriction or lageniform with obtuse apex, with 6–12 μm long pedicel, thin-walled, hyaline. Lamella edge sterile. Cheilocystidia 22 (25)–60 (65) × 10–19 (25) μm, narrowly clavate to clavate, rarely subutriform or fusiform, sometimes with up to 10 μm long pedicel, thin-walled, hyaline or with brown intracellular pigment. Pileipellis an euhymeniderm composed of sphaeropedunculate, ventricose to broadly clavate or ovoid elements with short neck, less frequently with clavate to narrowly clavate elements, very rarely broadly clavate with flexuous upper part or mucronate, 32–60 (64) × (9)20–41 (45) μm with brown intracellular pigment, thin-walled. Stipitipellis a cutis of 4–12(16) μm wide, made up of cylindrical thin-walled hyaline hyphae. Caulocystidia numerous, in tufts, over the entire stipe, densely covering upper part, sparse at very base, 25–100(112) × (8)10–20 μm, thin-walled, subcylindrical, narrowly clavate to clavate, fusiform or utriform, with brown intracellular pigment, rarely colourless. Clamp connections absent in all tissues.

Additional material examined:— FRANCE. Savoie, Motz, Réserve Naturelle des Iles de la Malourdie, on soil on path, riparian deciduous forest along a Fraxinus wood on peaty soil mixed with sand along a path, with Urtica and other nitrophilic plants, 22 May 1999, M. Durand & P.-A. Moreau, LIP 0401385 (PAM99052202); GenBank Number: MN250224 (ITS rDNA)

Habitat:—on rich soil under Corylus avellana or Fraxinus excelsior , without visible connection to wood.

Distribution:—So far only known from Slovakia and France.

Figures

FIGURE 2. Pluteus keselakii holotype BRNM 817402: a basidiospores, b basidia, c pleurocystidia, d cheilocystidia, e pileipellis elements, f caulocystidia. Scale bar = 10 μm. Illustrated by Hana Ševčíková.

FIGURE 3. Pluteus keselakii a–e holotype BRNM 817402 basidiocarps, f pleurocystidia holotype, g pileipellis LIP Mycologie 0401385, h–i Basidiocarps. LIP Mycologie 0401385, j caulocystidia holotype BRNM 817402. Scale bar: a–e, h–i = 1 cm, f–g and j = 10 μm. Photos: a–e Pavol Kešeľák, f–g and j Hana Ševčíková, h–i Pierre-Arthur Moreau.