Marasmius cystidiatus S. A. Sharafudheen & Manim., 2018

Sharafudheen, Shahina A. & Manimohan, Patinjareveettil, 2018, A new species of Marasmius section Globulares from Kerala State, India, Phytotaxa 364 (1), pp. 92-100 : 93-98

Marasmius cystidiatus S. A. Sharafudheen & Manim. , sp. nov. Figs. 1A–N

MycoBank MB 825258

Etymology:— cystidiatus (Latin) , with cystidia; refers to the presence of pleurocystidia in this species.

Diagnosis:—Characterized by a brownish orange pileus often with a finely cracked center at maturity, a pruinose stipe with many off-white basal strigose hairs, a mild, pleasant odour, a hymenium showing pleurocystidia, and a stipitipellis with non-setuloid caulocystidia and caulocystidioid side branches. Differing from M. midnapurensis in having smaller basidiospores (7–10 × 4–5 μm), subregular lamellar trama, a hymenium with pleurocystidia, a stipitipellis lacking Siccus - type broom cells, and a distinctive nrITS sequence (MH216042).

Holotype:— INDIA. Kerala State: Malappuram District, Calicut University Botanical Garden , 23 June 2016, Shahina A. Sharafudheen SA 13 ( CAL 1672 ). GenBank accessions: (nrITS: MH216042 ; nrLSU: MH275541 )

Description:— Basidiocarps small to medium-sized. Pileus 18.5–32 mm diam., convex when young, becoming broadly convex to plano-convex with or without a central depression; surface brownish orange (6C6/OAC652) all over when young, at maturity brown (6E6/OAC722) to brownish orange (5C6/OAC798) at the center and grayish orange (5B5, 5B4/OAC792) to almost brownish orange (6C6/OAC652) towards the margin; center smooth when young, but often finely cracked at maturity, translucent-striate to slightly sulcate-striate towards the margin; margin mostly decurved, occasionally upturned at maturity, crenate. Context up to 2 mm thick, soft, concolorous with the lamellae. Lamellae adnexed to adnate, up to 4.5 mm wide, pale yellow (4A3/OAC857), close; edge entire, concolorous with the sides; lamellulae in 1‒4 tiers. Stipe 48–68 × 1.5–4 mm, central, terete, hollow; surface brown (6 E8, 7 E7, 7 E4/OAC747, OAC699, OAC640) all over except for the apex where it is concolorous with the lamellae, pruinose all over, more so towards the base, base with several, off-white, strigose hairs; Odour mild, pleasant. Spore print white.

Basidiospores 7–10 × 4–5 (8.6 ± 0.74 × 4.51 ± 0.43) μm, Q = 1.4–2.25, Qm = 1.92, oblong-ellipsoid or lacrymoid, smooth, thin-walled, hyaline, inamyloid. Basidia 18.5–30 × 6–8 μm, clavate, hyaline to pale yellow, 4-spored; sterigmata up to 3 μm long. Lamella-edge sterile with crowded cheilocystidia. Cheilocystidia 18–37 × 4–10 μm, in the form of Siccus - type broom cells, clavate, cylindrico-clavate, subcylindrical or obclavate, sometimes branched, thick-walled at the apex, gradually becoming thin-walled towards the base, hyaline or yellowish brown at the apex, hyaline towards the base; setules up to 16 μm long, subacute to obtuse, sometimes branched and septate, yellowish brown, thick-walled (<1 μm). Pleurocystidia scattered, 16–37 × 4–9 μm, mostly flexuose, rarely clavate to narrowly clavate, often apically branched, pale yellow to hyaline, thin-walled. Lamellar trama subregular; hyphae 3.5–22 μm wide, thinto slightly thick-walled (<0.5 μm), hyaline, dextrinoid. Pileus trama interwoven; hyphae 3.5–27 μm wide, thin-walled, hyaline, dextrinoid. Pileipellis hymenodermic with Siccus - type broom cells; broom cells 17–41.5 × 6–17 μm, clavate, broadly clavate, cylindrico-clavate or subcylindrical, often branched, sometimes septate, thin- to slightly thick-walled (<0.5 μm) at the apex, thin-walled towards the base, hyaline, bearing obtuse apical setules; setules yellowish brown, up to 17 μm long. Stipitipellis a cutis disrupted by solitary or bunched caulocystidia and caulocystidioid side branches; hyphae 2–13 μm wide, yellowish brown, but hyaline at apex, thin- to thick-walled up to 1.5 μm. Caulocystidia 27– 65 × 4–8 μm, flexuose, sometimes with a mucronate apex, often branched, hyaline, thin- to thick-walled (<1 μm). Caulocystidioid side branches 7–43 × 4–8 μm, hyaline, thin- to thick-walled (<1 μm). Stipe trama dextrinoid. Clamp connections present on all hyphae.

Habitat: — Growing in small groups on decaying dicot twigs.

Geographical distribution range:—Known only from the type locality in Kerala State, India.

Additional specimens examined: — INDIA. Kerala State: Malappuram District, Calicut University Botanical Garden , 28 July 2016, Shahina A. Sharafudheen SA 82 ( CAL 1669 ). GenBank accessions: nrITS: MH216191 ; nrLSU: MH275542 .

Comments:—Non-collariate lamellae, a central, well developed, non-insititious stipe, and a pileipellis with Siccus - type broom cells place the present species in Marasmius section Globulares . The non-setuloid caulocystidia lead it to the series Atrorubentes ( Antonín & Noordeloos 2010) . A few members of Marasmius section Globulares series Atrorubentes such as M. midnapurensis Dutta, Pradhan & Acharya in Dutta et al. (2014: 119), M. inthanonensis Wannathes, Desjardin & Lumyong in Wannathes et al. (2009: 270), and M. araucariae Singer (1965: 333) share some characters with M. cystidiatus besides the typical sectional characters.

Marasmius midnapurensis , a species recently described from India ( Dutta et al. 2014), has light yellowish brown patches at the center of the pileus, larger basidiospores (10.7–15 × 3.5–4.7 μm), interwoven lamellar trama, lamellae devoid of pleurocystidia and Siccus - type broom cells in the stipitipellis.

Marasmius inthanonensis , a species described from Thailand ( Wannathes et al. 2009), differs from M. cystidiatus in having an olive brown pileus when young then fading through brownish orange to yellowish brown with age, yellowish gray lamellae with light brown edges, a subvelutinous to hispidulous stipe, an indistinct odour, absence of pleurocystidia, broom cells with short setules (2–6 μm), interwoven lamellar trama and habitat on dicot leaf litter.

Marasmius araucariae , a species originally described from Argentina ( Singer 1965) and later from Papua New Guinea ( Desjardin & Horak 1997) and Thailand ( Wannathes et al. 2009), can be distinguished from M. cystidiatus in having a pileus with rugulose, reddish brown to chestnut brown surface ( Singer 1965; Desjardin & Horak 1997), a relatively short (29–54 mm) stipe, absence of pleurocystidia ( Singer 1965; Desjardin & Horak 1997; Wannathes et al. 2009) indistinct odour, ellipsoid basidiospores with a mean size of 10.5 × 3.9 μm and interwoven lamellar trama ( Desjardin & Horak 1997; Wannathes et al. 2009). Marasmius araucariae var. siccipes Desjardin, Retnowati & Horak (2000: 173) has orangish brown lamellar edges and Siccus - type broom cells along with non-setuloid caulocystidia.

A megablast search of the GenBank nucleotide database using the ITS sequences of M. cystidiatus showed M. occultatiformis Antonín, Ryoo & Shin (2012: 616) ( Marasmius section Globulares series Leonini ) as the closest hit followed by Marasmius ochroleucus Desjardin & Horak (1997: 35) ( Marasmius section Globulares series Atrorubentes ) both with 94% identities. Marasmius occultatiformis , described from the Republic of Korea for the first time ( Antonín et al. 2012) and later from the Russian Far East ( Kiyashko et al. 2014), shows considerable variation in morphology and microscopic features. It has a relatively small, umbonate pileus with a finely tomentose surface and an inflexed margin, finely pubescent ( Antonín et al. 2012) or toothed ( Kiyashko et al. 2014) lamellar edges, a short stipe, lamellae devoid of pleurocystidia and a cutis-type stipitipellis lacking both caulocystidia and caulocystidioid elements. Marasmius ochroleucus , described from New Caledonia for the first time ( Desjardin & Horak 1997) and later from Northern Thailand ( Wannathes et al. 2009), differs from the present species in having smaller basidiocarps, an off-white to pale ochre or pale orange-ochre ( Desjardin & Horak 1997) or light yellow to cream ( Wannathes et al. 2009) pileus with an umbo, broadly fusoid ( Desjardin & Horak 1997) or ellipsoid ( Wannathes et al. 2009) basidiospores, an interwoven lamellar trama and lamellae devoid of pleurocystidia.

The phylogenetic tree inferred from the nrITS-based ML analysis ( Fig. 2 ) shows the two collections of M. cystidiatus nesting within the clade representing Marasmius sect. Globulares . Within this clade, infrasectional ranks were found to be polyphyletic supporting previous works ( Wannathes et al. 2009; Shay et al. 2017). However, M. cystidiatus forms a distinct lineage, sister to a cluster containing mostly members of the series Atrorubentes with 90% ML bootstrap support.

Figures

FIGURE 1. A–N: Marasmius cystidiatus. A. Basidiocarps; B. Basidiospores; C. Basidium; D–G. Pleurocystidia; H–I. Cheilocystidia; J. Pileipellis element; K. Pileipellis; L. Caulocystidia; M. Caulocystidioid side branch; N. Stipitipellis; Scale Bars: A=10 mm; B–J, L–M=10 μm; K & N= 20 μm. Photos by Shahina A. Sharafudheen.

FIGURE 2. ML phylogram based on nrITS sequence datamatrix showing the placement of M. cystidiatus within the genus Marasmius. Values at nodes indicate bootstrap support. BS values ≥50% are shown. Scale bar indicates the number of substitutions per site.