Cortinarius lentus (Agaricales, Cortinariaceae), a new species in section Calochroi Author Dovana, Francesco 0000-0002-8556-7692 Dipartimento di Scienze della Vita e Biologia dei Sistemi, Università di Torino, Viale P. A. Mattioli 25, 10125 Torino, Italy. francescodovana@libero.it Author Boccardo, Fabrizio 0000-0003-3686-5674 Via Filippo Bettini 14 / 11, 16162 Genova, Italy. micete@libero.it Author Clericuzio, Marco 0000-0003-3497-0999 Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale, Via T. Michel 11, 15121 Alessandria, Italy. marco.clericuzio@uniupo.it Author Vizzini, Alfredo 0000-0001-8390-6446 Institute for Sustainable Plant Protection (IPSP) - CNR, Viale P. A. Mattioli 25, 10125 Torino, Italy. alfredo.vizzini@unito.it text Phytotaxa 2020 2020-06-04 447 1 31 41 http://dx.doi.org/10.11646/phytotaxa.447.1.3 journal article 10.11646/phytotaxa.447.1.3 1179-3163 13878666 Cortinarius lentus Boccardo, Cleric., Dovana & Vizzini , sp. nov . ( Figures 3–6 ) MycoBank:—MB 835594 Type:— ITALY . Liguria , Savona, Sassello, gregarious on acidic soil under Castanea sativa , 06 October 2019 , leg. F . Boccardo , GDOR 4750 ( Holotype : GDOR !) Etymology:—the specific epithet “ lentus ” means “slow”, “sluggish” and refers to the slow and not bright chemical reactions with alkali reagents. FIGURE 3 . Cortinarius lentus . A–B Basidiomes in habitat.A Coll. GDOR 4750 (holotype). B Coll. GDOR 191. Photos:A by F. Boccardo; B by M. Clericuzio. Description:— Pileus 25–50(–55) mm diam., viscid-glutinous when wet, dry to slightly viscid in conditions of low humidity, glabrous with only inconspicuous fibrils at the edge, not hygrophanous; at first hemispheric to convex, later plano-convex, sometimes depressed, centre with a few whitish to pale yellow veil remnants, margin involute for a long time then inflexed; colour never entirely yellow (7.5 Y 9/4-8), rather orange-yellow (10 YR 8/4-6) to orange (10 YR 7/6-8), later becoming dark orange (10 YR 6/10), to brown-orange (10 YR 4/6). Margin generally slightly less coloured than centre, straw yellow. Lamellae crowded, emarginate to arcuate, edge even to slightly crenulated, bluish pink (7.5 PB 9/2) to light purplish (2.5 P 9/2-4) at the beginning, rapidly darkening to rusty brown with age. Stipe 20–50 × 8–15 mm , cylindrical, with a more or less abruptly marginate to rounded bulbous base, up to 25 mm diam long, white or pale cream with irregular ochraceous spots, sometimes with a soft bluish tinge in the upper part, solid, covered with yellowish-coloured fibrils of the partial veil; bulbipellis whitish to cream, yellowish universal veil on the bulb margin abundant, sometimes extending to the stipe; mycelial strands white. Cortina fairly sparse, white to cream, with age heavily covered with rust brown spore powder. Context whitish, sometimes with ochraceous spots in the bulb of older specimens. Macrochemical reaction 10% KOH on pileus surface of fresh basidiomes: on yellow areas ochraceous brown, on orange areas red-brown; ochraceous brown on bulb edge surface, in context negative to ochraceous. Smell earth/dust-like to rancid. Taste mild and unpleasant. FIGURE 4 . Cortinarius lentus . Basidiomes of coll. GDOR 4750 (holotype). Drawing by F. Boccardo. FIGURE 5 . Cortinarius lentus . A–B Terminal elements of pileipellis; C–F Spores. A–E Coll. GDOR4750 (holotype), F Coll. GDOR191. Scale bars: 10 μm. Photos: A–E by F. Dovana; F by M. Clericuzio. Spores [60/4/3] (8.2–)8.6–9.2–9.9(–11.0) × (4.0–)4.6–4.9–5.3(–5.9) µm, Q = (1.46–)1.74–1.87–2.00 (–2.20), amygdaliform to citriform, very rarely ellipsoid, almost always tapering at apex, distinctly and coarsely verrucose. Basidia 28–30 × 7–8 µm, clavate, four-spored, thin-walled and hyaline in KOH, sterigmata up to 4 µm long. Lamella edge more or less fertile. Hymenophoral trama consisting of cylindrical to subcylindrical hyaline hyphae, up to 10 µm wide. Cheilocystidia and pleurocystidia not observed. Pileipellis as a cutis, hyphae hyaline to dark yellow, cylindrical terminal elements 2.0–3.5(6) μm wide, generally with rounded apex, rarely subcapitate. Cytoplasmic and parietal pigment present. Clamp connections frequent at all septa. Habitat:—In deciduous forest with chestnut trees ( Castanea sativa ), on acidic soil. Additional specimens examined:— ITALY . Toscana , Grosseto , Roccastrada , loc. Sassoforte , under Castanea sativa , 2 October 2017 , leg. M . Clericuzio , GDOR191 ( GDOR !) ; ITALY , Liguria , Savona , Sassello , loc. Badani , under Castanea sativa , 25 October 2017 , leg. F . Boccardo , GDOR4501 ( GDOR !)