Entoloma magnum K.N.A. Raj & Manim.

MycoBank number: MB 818742 Facesoffungi number: FoF02637

Etymology: The specific epithet refers to the large size of the basidiocarp.

Holotype: CAL 1385

Basidiocarp large, tricholomatoid. Pileus 102 mm diam., somewhat plano-convex with a low central umbo surrounded by a shallow depression; surface dark brown (7F4/OAC636) at the centre and light brown (7D4/OAC659) towards the margin, not hygrophanous, tacky, finely radially wrinkled, innately fibrillose, plicate-striate towards the margin; margin somewhat incurved to almost straight, finely crenate, fissile. Lamellae narrowly adnate to adnate, moderately crowded, subventricose, orange white (6A2/OAC634), up to 13 mm wide, with lamellulae of 3 lengths; edge crenate to somewhat wavy, concolorous with the sides. Stipe 99 × 18 mm, central, terete, slightly tapering towards both the apex and the base, robust, solid; surface yellowish-brown (5D4/OAC743) towards the apex, whitish towards the base, appressed-fibrillose all over; base with scanty basal mycelium. Odour and taste not distinctive.

Basidiospores 7–10 × 7–9 (8.6±0.73 × 7.6±0.66) µm, Q = 1–1.2, Qm = 1.13, predominantly pentagonal or occasionally 4- or 6-angled in profile, isodiametric to sub-isodiametric, hyaline, thick-walled. Basidia 31–57 × 9–11 µm, clavate, hyaline, thin-walled, 4-spored; sterigmata up to 7 µm long. Lamella-edge fertile. Cheilocystidia and pleurocystidia absent. Lamellar trama subregular; hyphae 4–7 µm wide, pale brownish-yellow, thin-walled. Subhymenium inconspicuous. Pileus trama subregular; hyphae 7–13 µm wide, pale yellow, thin-walled. Pileipellis a transition between an ixocutis and an ixotrichoderm; hyphae 5–10 µm wide, with a pale brownish-yellow wall pigment, thin-walled. Stipitipellis a cutis rarely disrupted with flaring out hyphae; hyphae 5–12 µm wide, pale brownish-yellow, thin-walled. Caulocystidia absent. Oleiferous hyphae present in both lamellar and pileus trama. Clamp connections observed on all hyphae.

Habitat: on soil, among litter, solitary.

Material examined: INDIA, Idukki District, Munnar, Eravikulam National Park, 6 July 2011, K.N. Anil Raj AR683 (CAL 1385, holotype). GenBank number ITS:KY002062.

Notes: Entoloma magnum is characterized by a large, tricholomatoid basidiocarp; a brown-coloured, umbonate pileus; adnexed to narrowly adnate lamellae; a fleshy-fibrous stipe; isodiametric to sub-isodiametric basidiospores; absence of cheilocystidia; a pileipellis that is a transition between an ixocutis and an ixotrichoderm and the presence of clamp connections on all hyphae. Owing to these characters, E. magnum fits into the section Entoloma of the subgenus Entoloma (Noordeloos 2004; Co-David et al. 2009; Noordeloos and Gates 2012).

Entoloma brihadum Manim., A.V. Joseph & Leelav., a species previously described from Kerala (Manimohan et al. 1995), somewhat resembles E. magnum in having robust, tricholomatoid basidiocarps with a subumbonate pileus, crowded lamellae, a fertile lamella-edge, and absence of caulocystidia. However, E. brihadum has a smaller (50 mm), pinkish-white, glabrous pileus with pellucid striations, free to adnexed lamellae, a pinkish-white, and glabrous stipe, smaller and exclusively quadrate basidiospores (6–8 × 6–7 µm) and a cutis-type pileipellis composed of hyaline hyphae.

Entoloma myochroum Noordel. & E. Ludw., a species from Germany (Noordeloos 2004), is close to E. magnum in having almost similar-sized basidiocarps, a concave and glabrous pileus, adnate lamellae with concolorous edges, a solid stipe with a fibrillose surface, almost similar-sized basidiospores (7–10 × 6.5–8.5 µm) with 4–6 angles, a fertile lamella-edge and clamped hyphae. However, that species has a mouse-grey-coloured pileus, a flexuous or irregularly shaped stipe, a cutis-type pileipellis made up of hyphae with intracellular pigment and lamellar and pileus trama with short inflated elements.

In a BLASTn search using the ITS sequence (628 bp) derived from E. magnum, the closest hit was E. ochreoprunuloides (GenBank number KC710092; 92% identity). Entoloma ochreoprunuloides Morgado & Noordel., is a species from Germany (Noordeloos 2004; Morgado et al. 2013), resembles E. magnum in having a similar-shaped, brownish pileus with radially wrinkled and innately fibrillose surface, isodiametric basidiospores, a fertile-lamella edge, and clamped hyphae. However, E. ochreoprunuloides differs from E. magnum owing to its smaller-sized and differently-coloured basidiocarps, emarginate lamellae, smaller (5.9–7.1 × 5.7–7.2 µm) basidiospores and hyphae of the pileipellis with intracellular pigment.

In the phylogram generated from the ML analysis, E. magnum nested within a clade, which represents the subgenus Entoloma. Within this clade, E. magnum, E. luteobasis, E. ochreoprunuloides, E. madidum and collections of E. bloxamii formed a subclade. Within this subclade, E. magnum was differentiated as an independent lineage separated from other species with significant (74%) bootstrap support.

ITS-based phylogram generated from maximum likelihood analysis using RAxML-HPC2 v. 8.2.8 (Stamatakis 2014) on XSEDE platform employed in CIPRES Science Gateway web server (Miller et al. 2010) depicting the placement of Entoloma magnum (KY002062) within Entoloma subg. Entoloma. Bootstrap support values ≥ 50% are indicated at the nodes. The tree is rooted with Rhodocybe luteobrunnea, R. tugrulii, Clitopilus prunulus and C. reticulosporus.

Entoloma magnum (CAL 1385, holotype). Scale bar = 20 mm (Photo by K. N. Anil Raj).

Entoloma magnum (CAL 1385, holotype). a Basidiospores. b Basidium. c Stipitipellis. d Pileipellis. Scale bars: a, b = 10 µm; c, d = 100 µm (Photos by K. N. Anil Raj).