Tephrocybella griseonigrescens Picillo, Vizzini & Contu, in Crous et al. Persoonia 34: 231 (2015)
Etymology. From Latin: griseus and nigrescens, referring to the grey colour of the pileus and to the blackening of the lamellae on bruising, respectively.
Pileus 1.5–4.3 cm, subcampanulate to parabolic to convex, never fully applanate, occasionally with a shallow depression on disc, non-hygrophanous, margin entire, smooth, not translucent-striate, long inrolled, surface with a finely matted overlay of a pale greyish colour, tending to become areolate with age so revealing the brownish grey, bistre-brown, even liver brown colour of the underlying pellis. Lamellae adnate to shortly decurrent with a tooth, medium crowded, narrow, slightly falcate, with lamellulae of variable length, whitish to pale beige in young specimens, then of a deeper beige, tending to develop brownish spots with age, starting from the end attached to the stipe, strongly blackening on bruising, separable from the pileus context all together, edge smooth, concolorous. Stipe 2.3–4.7 × 0.3–0.8 cm, central, sometimes eccentric, cylindrical, slightly enlarged at base, often flattened lengthwise, fistulose, surface white pruinose at the apex, fibrillose elsewhere, strigose at base due to the presence of distinct white, wholly hairs, in mature specimens tending to discolour brown throughout starting from the base. Context brittle, chalky, fibrous in the stipe, whitish beige in the central part, concolorous with the external surface in the cortex, soon brownish in stipe base. Odour faint, aromatic-fruity, at times vaguely reminiscent of Inocybe bongardii or faintly mealy, taste mild. Spore-print white. Spores (n = 32) (3.2–)3.5–4.5(–5) × (1.5–)2–2.5(–3.0) μm, Q = 1.64–1.86, Qm = 1.75, narrowly ellipsoid with suprahilar depression in side-view, narrowly ellipsoid in front-view, apiculus hardly prominent, mono- or multiguttulate, walls smooth, slightly thickened, strongly cyanophilic, inamyloid and non-dextrinoid. Basidia 15–23 × 4–5.5 μm, 2- or 4-spored, narrowly clavate, with siderophilous granulations, clamped at base, sterigmata up to 4 μm long. Subhymenium pseudoparenchymatic. Hymenophoral trama regular, consisting of short, subparallel, cylindrical hyphae, often constricted at septa, smooth, moderately thick-walled, slightly dextrinoid, 2.5–12.5 μm wide. Cheilocystidia present but rare and far between, in some specimens almost absent, subcylindraceous to lageniform, 31–41 × 3.5–6 μm, upper portion up to 17 μm long, walls thin and smooth. Pleurocystidia none. Pileipellis. Suprapellis a xerocutis of cylindrical, slightly interwoven, shortcelled hyphae, 1.5–7.5 μm wide, with slightly thickened walls (0.5–0.6 μm), slightly dextrinoid, with some rising terminal element. Subpellis almost undifferentiated, with hyphae up to 15 μm wide. Pigment exclusively vacuolar. Caulipellis constituted by a cutis of parallel, cylindrical, smooth, short-celled hyphae, 1.5–6.5 μm wide, walls slightly thickened, slightly dextrinoid, with some rising terminal elements. Caulocystidia none. Clamp connections present everywhere, but not numerous. Thromboplerous hyphae none.
Index Fungorum number: IF812273
Notes: BP refers to the personal herbarium of B. Picillo. Phylogenetic hypotheses were constructed with Bayesian inference (BI) and Maximum likelihood (ML) criteria (MrBayes 3.2.2 and RAxML 7.3.2). As both Bayesian and Maximum likelihood analyses produced the same topology, only the Bayesian tree with both Bayesian posterior probabilities and Maximum likelihood bootstrap values are shown. Based on the combined ITS-rpb2 analysis Tephrocybella griseonigrescens clusters with Lyophyllum cf. maas-geesterani sister to a clade consisting of Lyophyllum maas-geesterani and Calocybe (type C. gambosa). Tephrocybella griseonigrescens, characterised by greyish collybioid basidiomes, context turning black on handling, vacuolar pigmentation and presence of sublageniform cheilocystidia, superficially resembles some species of the genus Tephrocybe (type T. rancida) but sharply differs in having intracellular and not intraparietal and/or incrusting pigment in the hyphae of the pileipellis (Consiglio & Contu 2002, Kalamees 2004) and in ITS and rpb2 sequences. Lyophyllum maas-geesterani, with blackening basidiomes, is phylogenetically close to Tephrocybella griseonigrescens, but differs in having yellowish lamellae, more elongate, ellipsoid-elongate to subcylindrical basidiospores, irregularly fusiform, smaller cheilocystidia and incrusting pigment in the pileipellis (Clémençon & Winteroff 1992). For phylogenetic tree (sequences selected following Bellanger et al. 2015).
Figure 1. Bayesian phylogram of the lyophylloid taxa close to Tephrocybella. The combined data matrix consists of ITS and rpb2 regions. For the accession numbers of the sequences retrieved from GenBank refer to Bellanger et al. (2015).
Figure 2. Colour illustrations. Castel Fusano, Rome, mixed wood with Pinus pinea and Quercus ilex, with Phyllirea angustifolia, Laurus nobilis, Cistus incanus, Erica arborea and Ruscus aculeatus, where the holotype was collected (B. Picillo), basidiomata, areolate pileus surface, stipe base with wholly hairs, spores and cheilocystidium (all from holotype). Scale bars = 1 cm (basidiomata), 10 μm (microscopic elements). All photos by B. Picillo.
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