Lyophyllum agnijum K.N.A. Raj, K.P.D. Latha & Manim., sp. nov.
Index Fungorum number: IF 559692; MycoBank number: MB 559692; Facesoffungi number: FoF10842; Fig. 1
Etymology – “agnijum” means born in fire in Sanskrit, referring to the occurrence of the basidiocarps on a burned substratum.
Macromorphology – Basidiocarps small, omphalinoid. Pileus 3–8 mm diam., convex or hemispherical with a small, distinct umbo; surface greyish brown (6F3/OAC640) all over when young, becoming greyish brown at the centre (6F3/OAC640) and dark brown (6F5/OAC734) elsewhere, hygrophanous and becoming paler, finely striate, appressed-fibrillose all over; margin initially incurved, becoming decurved, crenate. Lamellae emarginate with a small decurrent tooth, close, greyish brown (6D2/OAC723) when young, becoming brownish grey (6C2/OAC669) at maturity, up to 3 mm wide, with lamellulae of 3 lengths; edge finely torn, concolourous with the sides. Stipe 9–40 × 1–2 mm, central, terete, equal or slightly tapering towards the base, fistulose; surface greyish brown (6F3/OAC640) when young, becoming light brown (6D4/OAC646), longitudinally fibrillose, white-furfuraceous at the apex; base slightly enlarged, whitish. Context up to 1 mm thick. Odour and taste not distinctive. Spore print not obtained.
Micromorphology – Basidiospores 5–6(6.5)×5–5.5(6.5) (5.47±0.44×5.12±0.27) µm, Q=1–1.2, Qm=1.06, subglobose to globose, smooth, cyanophilous, thin- to slightly thick-walled, inamyloid. Basidia 24–34×6.5–8 µm, clavate, hyaline, thin-walled, siderophilous, 1-, 2-, 4-spored; sterigmata up to 9 µm long. Pleurocystidia absent. Lamella edge heterogeneous, fertile basidia intermixed with scarce, hard-to-detect cystidia. Marginal cells (Cheilocystidia) 10–28 × 3–7 µm, versiform: clavate, flexuose, narrowly utriform, filiform or sometimes septate, hyaline, thin-walled. Lamellar trama with a broad mediostratum composed of subregular compactly arranged hyphae, slightly but distinctly gelatinized towards the subhymenium; hyphae 3.5–11 µm wide, hyaline, thin-walled, inamyloid. Pileus trama subregular; hyphae 2–10 µm wide, hyaline, hyaline or with a pale-yellow wall pigment, thin- to slightly thick-walled, inamyloid. Pileipellis a cutis; hyphae 3.5–17 µm wide, with yellowish brown wall pigment and yellowish-brown spiral encrustations, thin- to slightly thick-walled. Stipitipellis a cutis disrupted by short trichodermial patches towards the apex; hyphae 3–8 µm wide, with a pale yellowish brown wall pigment. Terminal elements 22.5–44×4–7 µm, hyaline, thin- to slightly thick-walled. Caulocystidia absent. Clamp connections observed on all hyphae.
Habitat and distribution – gregarious, often as small clusters, on charred bamboo clumps, in tropical broad-leaved forests.
Materials examined – India, Kerala State, Wayanad District, Kuruva islets on the river Kabani, 6 July 2015, K.P. Deepna Latha and K.N. Anil Raj DKP356 (CAL 1388, holotype).
GenBank numbers – ITS: MK860709.
Notes – In the traditional infra-generic classification of Lyophyllum, the dull-coloured, caespitose basidiocarps and the smooth, globose basidiospores of our collection L. agnijum places it in the subsection Difformia of section Difformia (Kalamees 2004; Knudsen and Vesterholt 2008; Sesli et al. 2015). Lyophyllum atratum (Fr.) Singer, a widespread carbonicolous species described from different parts of Europe, North America, Australia and New Zealand (Singer 1943; Cooper 2014), shares a few features such as brownish basidiocarps with a fibrillose pileus, a cylindrical stipe that is tapered towards the base, inamyloid and somewhat similar-sized basidiospores (5.5–7.5×3.5– 5.5 μm) and clamped hyphae, with L. agnijum. However, L. atratum differs from L. agnijum in having larger basidiocarps (pileus 20 mm diam., and stipe 10–20×1–3 mm), a pileus with striations that are confined to the margin, adnate lamellae, a hollow stipe, a strong, rancid odour, ellipsoid basidiospores, lamellae devoid of cystidia and consistently 4-spored basidia.
Lyophyllum ambustum (Fr.) Singer, another carbonicolous species distributed in Europe and India, seems to be closely related to L. agnijum in having brownish basidiocarps with an umbonate, hygrophanous pileus, rather similar-sized basidiospores (5.5–8×5–6.5 μm), hyphae of pileipellis with brown encrustations and a gregarious habit. However, L. ambustum has larger basidiocarps (pileus up to 20 mm diam., stipe 25–45 ×1.5–2.5 mm), translucent-striate pileus, dry, almost whitish grey when mature and with a denticulate margin, broadly adnate lamellae with smooth edges, a stipe with white fibrous flakes which is hollow when mature, a flour-like odour, tuberculate-verrucose basidiospores, a lamella-edge without cystidia and the absence of clamp connections (Moser 1983; Breitenbach and Kränzlin 1991a). Lyophyllum anthracophilum (Lasch) M. Lange & Sivertsen, a carbonicolous species reported from Europe, North America, Africa and Asia, is similar to L. agnijum in having brown-tinted basidiocarps with a striate, hygrophanous pileus, a longitudinally fibrillose stipe which is furfuraceous at the apex, globose to subglobose basidiospores, a pileipellis composed of parallel hyphae, the presence of clamp connections and a gregarious habit. Lyophyllum anthracophilum, however, is distinguished from L. agnijum by its larger basidiocarps (pileus up to 30 mm diam., stipe 30–50×1.5–2 mm) with black-brown pileus and stipe, a non-umbonate pileus which becomes applanate with age, broadly adnate to subdecurrent, grey-white lamellae with a smooth edge, smaller basidiospores (4.8–5.7×4.5–5.5 μm) and lamellae devoid of cystidia (Moser 1983; Breitenbach and Kränzlin 1991b).
The closest hit of our collection in the Blastn search was Lyophyllum decastes. Lyophyllum decastes is a species complex that includes several lineages and this has caused considerable taxonomic confusion in the past (Larsson and Sundberg 2011). Therefore, a morphology-based comparison of L. decastes is not useful. In our ML analyses (Fig. 2), our collection was grouped with L. littorale (ML=66%) representing a well-differentiated clade from L. decastes species complex with ML=98% bootstrap support. Lyophyllum littorale (Ballero & Contu) Contu, a species described from Sardinia in Italy, shares some characters such as close, decurrent lamellae, a fibrillose stipe with pruina restricted to the apex, globose to subglobose basidiospores (4.5–6.3×4.5–5.7 μm), clamped hyphae and a gregarious habitat. However, L. littorale is distinguished from our collection in having large (pileus 15–65 mm diam., stipe 20–60×4–8 mm), grayish basidiocarps fruiting on calcareous soil, a non-hygrophanous pileus with a depressed centre and pruinose surface devoid of striations, a stipe which is tapered towards the apex and an orange-yellow base, 4-spored basidia and slightly gelatinized pileipellis (Ballero and Contu 1990). Lyophyllum atratum, L. anthracophilum, L. ambustum, and the other carbonicolous species treated in the present phylogenetic analyses, seem to be phylogenetically unrelated with our collection and hence we introduce our collection as L. agnijum.
Figure 1 – Lyophyllum agnijum (CAL 1388, holotype). a Basidiocarps in their natural habitat. b Basidiospores. c Basidia. d Marginal cells. e Pileipellis. f Stipitipellis towards the apex of the stipe. Scale bars: a=10 mm, b–d=10 µm, e–f=20 µm
Fig. 2. ML phylogeny based on nrITS sequence dataset depicting the placement of Lyophyllum agnijum. The newly sequenced species is displayed in bold face. ML bootstrap values are shown. Scale bar indicates the number of substitutions per site.