Cortinarius roseobasilis – Facesoffungi number: FoF 02042

Cortinarius roseobasilis Ammirati, Beug, Niskanen & Liimat

Index Fungorum number: IF 1551706 Facesoffungi number: FoF 02042

Etymology: Name based on reddish stipe base.

Holotype: Michael Beug 20MWB111813 (WTU) 

Pileus 42–75 mm diam., obtuse-umbonate to planoumbonate then uplifted-irregular umbonate, margin decurved to straight, becoming lacerate-split in age, non–striate or only short striate at edge in a few places, very little veil materials on edge, silky dry, colour Blackish Brown to Dusky Brown or Dresden Brown streaked with light ochraceous buff where faded, edge grayish to greyish brown, hygrophanous. Lamellae adnexed with a decurrent line, distant, thick, becoming irregular, deep brown with Vinaceous Drab mixed in, becoming Dresden Brown. Stipe up to 80 mm (often 70–80 mm) long, above up to 8 (or sometimes to 20) mm thick, equal above, strongly tapered to base, with some dull whitish fibrillose areas, otherwise buffy brown to lighter brown then watery brown to watery vinaceous brown. Universal veil white, sparse. Basal mycelium white. Context of pileus thin, watery and concolour, faded whitish, in stipe drab with pale drabgraystreaks,hollow. Odour not distinctive. Taste mild or not distinctive. Macrochemical reaction (40 % KOH): pileus cuticle fuscous, pileus context buffy brown, stalk apex pale ochraceous salmon, stipe base fuscous black. Exsiccatae: pileus dark brown to blackish, lamellae brown to dark brown, stipe pallid, brownish or blackish, lower stipe whitish in one, context pallid to darkened in lower stipe. Basidia 4-spored, 6.5–8×28–31μm, clavate, hyaline or slightly brownish. Basidiospores 6.7–8.9×4.5–4.8 (5.5) μm (20 spores, holotype specimens), ellipsoid, broadly ellipsoid, rarely subglobose, slightly curved apiculus, coarsely verrucose, moderately to very strongly dextrinoid. Lamella trama hyphae hyaline to yellowish brown or brownish, somewhat encrusted in KOH. Pileipellis in KOH: Surface layer thin, hyphae cylindrical, 5.2–9 μm wide, hyaline or yellowish, some slightly encrusted. Subtending layer of±enlarged hyphae 8.9– 26μm wide, hyaline, walls refractive, somewhat yellowish beneath a light yellow brown to light brown pigmented layer of cylindrical to enlarged hyphae, 4.5–25μm wide adjacent to trama hyphae. ITS sequence distinct from the other known members of the Castanei, and differs from them in the ITS region by more than 7 substitutions and indel positions.

Ecology and distribution: Gregarious under Quercus garryana or in mixed forests of Q. garryana, Crataegus, and Populus tremuloides. Producing basidiomata in late autumn. Known from Washington USA, Western North America.

Material examined: USA, Washington. Klickitat County, Balch Farm, 45°42.896 N, 121°18.939 W, Quercus garryana with Populus and Crataegus, 20 Nov 2010, leg. Joseph F. Ammirati JFA13666 (WTU, K). Klickitat County Lower Staats Road, N45°50′39″W121°24′50″, Quercus garryana, 18 Nov 2013, leg. Michael Beug 20MWB111813 (holotype, WTU), (isotype, K).

Notes: In our phylogenetic analysis C. roseobasilis is placed in Castanei although the group is not well-supported. However, the species in the group are morphologically similar. They have darkbrown to blackishbrown pileus; reddening, but first white, universal veil and/or stipebase; and indistinctive smell in lamellae. Cortinarius rosebasilisis most reminiscent of European C. erubescens M.M. Moser, but the spores of C. erubescens are narrowly ellipsoid and almost smooth.