Marasmius luculentus A.K. Dutta, K. Acharya & Antonín

MycoBank number: MB 816959 Facesoffungi number: FoF 2192

Etymology: referring to the beautiful (luculentus) appearance of the pileus.

Holotype: CUH AM120

Pileus 5–10 mm in diam., conic to hemispherical when very young, becoming convex in age, with a small conic to convex papilla that ranges from reddish-brown (8D6) to violet brown (10E5–6, 11E6–7) when young, but later turning brown (7D7, 7E8) to dark brown (7F7) at maturity, very rarely forming a central dot, often with a depression around the papilla; striate to plicate up to center, margin often crenate; surface dry, glabrous, hygrophanous, brownish-orange (7C4) to light brown (7D5–6) when very young, later reddish-grey (7–8B2) and finally turning white (1A1) to off-white at maturity, greyish-yellow (1–2B4, 4B4–5) on drying; context very thin, white to cream. Lamellae adnexed or adnate to a collarium, distant to subdistant (L = 12–14, l = 0), white (1A1), regular, slightly intervenose, edge concolorous. Stipe 5–9 (–12) × 0.1–0.3 mm, central, glabrous, wiry, pliant, cylindric, equal, simple and insititious on the substratum, dark brownish-black to black overall, often accompanied by black rhizomorphs, 30–42 mm long. Odour and taste indistinct. Spore print white.

Basidiospores (9.3–) 10–10.3–10.5 (–11) × (3.9–) 4.3–4.8–5.4 (-5.8) µm, Q = 1.7–2.2–2.6, ellipsoid to ellipsoid-fusoid, smooth, hyaline, IKI-, thin-walled. Basidia not observed. Basidioles 24–25 × 5.5–7 µm, fusoid to clavate, hyaline, thin-walled. Lamellae edge sterile. Pleurocystidia absent. Cheilocystidia composed of Siccus-type broom cells; main body 14–18 × 4–6 (–7.5) µm, sphaeropedunculate to (broadly) clavate or irregular in outline, hyaline, apically thick-walled; apical setulae 2–3.5 (–5.5) µm long, cylindrical or irregular in outline, obtuse, pale yellow to light brown in KOH, thick-walled. Pileipellis a hymeniform layer, composed of Siccus-type broom cells; main body (17–) 19–23 (–25) × (7–) 8–11 (–14.5) µm, sphaeropedunculate to clavate, broadly clavate, often branched, pale yellow to light brownish in KOH, thick-walled; apical setulae (1.5–) 3–4 (–5.5) µm long, cylindrical, obtuse, thick-walled. Pileus trama composed of 4.5–7.5 µm broad, interwoven, cylindrical, hyaline, inamyloid, thin-walled hyphae. Lamellar trama hyphae 4–6.5 µm broad, interwoven, cylindrical, hyaline, inamyloid, thin-walled. Stipitipellis hyphae 5.5–6.5 µm broad, parallel to subparallel, cylindrical, smooth, non-gelatinous, hyaline to pale yellow in KOH, non-dextrinoid to weakly dextrinoid, thick-walled. Stipe trama hyphae 6.8–7.5 µm broad, parallel to subparallel, cylindrical, smooth, non-gelatinous, hyaline, inamyloid, thin- to thick-walled. Caulocystidia absent. Clamp connections present in all tissues.

Material examined: INDIA, West Bengal, North-24-parganas, Barasat, Berunanpukhuria, N 22 44′ 22.7832″, E 88 26′ 25.2384″, 10.809 m alt., on dried leaves of Bambusa bambos (L.) Voss plant, A.K. Dutta & S. Paloi, 25 June 2015, AKD 100/2015 (CUH AM120, holotype). INDIA, West Bengal, North-24-parganas, Barasat, Berunanpukhuria, N 22 44′ 21.642″, E 88 26′ 26.6676″, ca 10.747 m alt., on dried leaves of B. bambos plant, A.K. Dutta & S. Paloi, 29 June 2015, AKD 132/2015 (CUH AM125, paratype). GenBank numbers CUH AM120 ITS: KX138604; LSU:KX138606. CUH AM125 ITS:KX138605.

Notes: Distinctive features of M. luculentus include a small basidiomes with a convex, plicate, light brown to reddish-grey pileus when young that later turns into white to off-white, with a reddish-brown to brown or dark brown central papilla, collariate and distant to subdistant, often intervenose lamellae (12–14), a small central, insititious stipe arising directly from the substratum, obtuse apical setulae of the pileipellis broom cells and cheilocystidia of the Siccus-type, and moderately-sized basidiospores (10.3 × 4.8 µm; mean Q = 2.2). These combinations of macro- and micro-morphological features easily categorizes the present specimen belonging to sect. Marasmius and subsect. Sicciformes Antonín (Wannathes et al. 2009).

Being a well representative of sect. Marasmius, the new Indian species is morphologically similar to several other species. Marasmius conicopapillatus Henn., described from Cameroon for the first time (Hennings 1895) and later subsequently reported to occur in other African countries (Antonín 2007), Bolivia (Singer 1976), Uganda (Pegler 1977) and Java (Desjardin et al. 2000) differs by its much smaller pileus (1–7 mm diam.) coloured pure white to off-white when young that turns cream-buff at maturity, non-intervenose lamellae, and a considerably larger stipe (12–30 mm long, Desjardin et al. 2000; 22–35 mm long, Pegler 1977) coloured white towards apex. Marasmius pallenticeps Singer, originally described from Argentina, has a much smaller pileus (1–2 mm diam.), a copper brown to reddish-brown coloured stipe that arise directly from the rhizomorphs, and distinctly smaller basidiospores (7–8.5 × 2.7–4.5 µm; Singer 1976). Marasmius chrysochaetes Berk. & M.A. Curtis differs by its much smaller pileus (1.2–2 mm), a longer stipe (22–25 mm long), and differently sized basidiospores (9–10 × 3–3.5 µm, Dennis 1951; 8–9 × 3.5–4.2 µm, Singer 1976). Marasmius stypinoides Petch, described from Hakgala, differs by its much smaller (up to 5 mm diam.) and minutely rugulose pileus, a longitudinally striate and initially white stipe, and a serrate lamellae edge (Petch 1948). Marasmius gracilichorda Corner has smaller basidiomes with a minutely velutinous pileus surface coloured brownish-orange to dark brown overall, yellowish-white lamellae with brownish edges (Tan et al. 2009).

Among other species that grows on bamboo leaves, Marasmius kuthubutheenii Y.S. Tan, Desjardin, Vikineswary & Noorlidah differs by its much smaller (1–3 mm) pileus with a minutely pruinose surface coloured brownish-orange to light brown overall and a very smaller stipe (2–4 mm long; Tan et al. 2009). As revealed, M. luculentus appears to be phylogenetically close to several other taxa like M. nigrobrunneus (Pat.) Sacc., M. ruforotula Singer, and M. subruforotula Singer. Marasmius nigrobrunneus, originally described from Vietnam and previously reported from India, differs by its smaller pileus (1–4 mm diam.) coloured greyish-black to brown black with slightly paler striae, a long slender stipe (up to 73 mm long), and somewhat differently sized basidiospores (Singer 1976; Manimohan and Leelavathy 1989; Antonín and Buyck 2006; Antonín 2007). Marasmius ruforotula has a greyish-orange to brownish-orange pileus with a black papilla, and yellowish-white lamellae, and presence of numerous black rhizomorphs (Tan et al. 2009). Marasmius subruforotula has a minutely velutinous pileus surface coloured greyish-brown to orange brown often with white striae, discoloured and pale orange coloured lamellae edge, slightly smaller basidiospores with a mean of 9.5 × 4.5 µm (Q mean 2.1), and habitat on dicotyledonous leaves or on wood (Pegler 1977; Antonín 2007; Wannathes et al. 2009).

The new species is macro-morphologically similar to M. capillaris, M. limosus, M. rotalis, and M. rotula, but the latter have cheilocystidia and pileipellis broom cells of the Rotalis-type, and belong in subsect. Marasmius (Petch 1948; Gilliam 1976; Singer 1976; Pegler 1977, 1986; Desjardin 1989; Bas et al. 1995; Corner 1996).

Phylogram generated from maximum likelihood (RAxML) analysis using a GTR+I+G model of nucleotide evolution based on ITS for 55 Marasmius and two outgroup sequences (Crinipellis brunneipurpurea and C. malesiana). Maximum likelihood bootstrap support values greater than 50% and Bayesian posterior probabilities greater than 0.5 are indicated above or below the nodes. Numbers to the left of / are ML bootstrap percentages, and those to the right are Bayesian posterior probabilities. Sequences used in this study mostly have been sampled from a previous study (Tan et al. 2009; Wannathes et al. 2009). The newly generated sequences are in blue, and the newly described taxa is placed in bold font to highlight its phylogenetic position in the tree. GenBank accession numbers for all of the sequences are indicated in the tree. G – sect. Globulares; L – sect. Leveilleani; MM – sect. Marasmius subsect. Marasmius; MS – sect. Marasmius subsect. Sicciformes; N – sect. Neosessiles; SA – sect. Sicci ser. Atrorubentes; SH – sect. Sicci ser. Haematocephali; SL – sect. Sicci ser. Leonini; and SS – sect. Sicci ser. Spinulosi.

Marasmius luculentus (CUH AM120, holotype). Habit (AKD 100/2015) (photo A.K. Dutta)

Marasmius luculentus (CUH AM120, holotype). a Basidiomata. b Basidiospores. c Siccus-type cheilocystidia. d Siccus-type cells of the pileipellis. Scale bars: a = 5 mm, b-d = 5 µm. (drawings A.K. Dutta)