Marasmiellus palmivorus (Sharples) Desjardin, Mycologia 97: 670 (2005)
Index Fungorum number: IF613706; MycoBank number: MB613706; Facesoffungi number: FoF 09970; Fig. 1
≡ Marasmius palmivorus Sharples, Malay. agric. Journal 16(nos 9–10): [1] (1928).
Pileus 10–25 mm in diam., hemispherical to convex, expanding to plano-convex, in age depressed to subumbilicate; margin initially smooth, soon striate to sulcate or rugulose-striate, sometimes wavy or cleft; surface dull, moist to dry, glabrous to felted or radially appressed-fibrillose, subhygrophanous; when young white (4A1) to pale yellow (4A2) or more commonly orange white (6A2), in age retaining pinkish white (7A2) or light orange (6A4) tones on the disc. Context up to 1 mm thick, soft, pliant, white (4A1). Lamellae horizontal, adnate, distant with 1–3 series of lamellulae, often intervenose in age, rarely forked, broad (2–4 mm), white (4A1), sometimes discoloring pinkish white (7A2) or light orange (6A4). Stipe 1.5–7×1–1.5 mm, central to eccentric, terete, cylindrical, base often enlarged, curved, solid, tough, subinsititious or arising from a pad of appressed white to pale orange mycelium; surface dull, dry, glabrous or minutely silky-pruinose, at first white overall, base darkening in age to greyish red (7B3), reddish orange (7B6–7B7) or reddish brown (8F5); often with fanlike white mycelium over substrate. Odour not distinctive. Basidiospores 8–12×4.5–6 μm, Q=1.7–2.3, Qm=1.95±0.1, ellipsoid, smooth, hyaline, inamyloid, thin-walled. Basidia 20–34 × 6–10 μm, clavate, 2 to 4-spored. Pleurocystidia absent. Cheilocystidia 17.5–24 × 8–12 μm, clavate with numerous apical setulae, hyaline, inamyloid, thin-walled; setulae 1.5–3.5×1–3.2 μm, irregularly cylindrical or knoblike, sometimes forked, obtuse to acute, hyaline. Pileipellis a cutis of loosely interwoven, repent hyphae, not a hymeniform layer, not a Rameales-structure; hyphae 4–12 μm in diameter, cylindrical, non-diverticulate, smooth or incrusted with annular to helical hyaline or yellow pigments; walls hyaline, inamyloid, non-dextrinoid, non-gelatinous; thin-walled; terminal cells undifferentiated, cylindrical. Pileus trama interwoven, lamellar trama regular; hyphae 3–15 μm in diameter, cylindrical or inflated, smooth, hyaline, inamyloid, non-dextrinoid, non-gelatinous, thin-walled or with walls up to 1 μm thick. Stipe trama 3–6.5 μm in diameter, cylindrical, parallel, nondiverticulate, smooth, hyaline, inamyloid, non-dextrinoid, non-gelatinous, thin-walled; medullary hyphae similar but many fusoid, up to 20 μm in diameter, some with walls up to 1 μm thick. Caulocystidia scattered, 25–30×5–8.5 μm, cylindrical to clavate or fusoid, non-diverticulate, hyaline, thin-walled. Clamp connections present in all tissue type.
Habitat – scattered on rotten coconut palm wood or fruits, on leaves and stems of banana and Lagerstroemia tree, or on undetermined woody debris in coastal coconut groves and banana-cacao groves.
Distribution – Known from Africa (São Tomé), India, Indonesia (Java), Malaysia, Taiwan, Thailand and USA (Hawaiian Islands) (Wilson and Desjardin 2005; Desjardin and Perry 2017; Dutta and Achaya 2018; Pham et al. 2019).
Material examined – THAILAND, Chiang Mai Province, Muang District, Chiang Mai University, 18°48′10″ N 98°57′23″ E, 334 msl, 15 June 2018, on the rotten wood, J. Kumla and N. Suwannarach, SDBR-CMU-NK076 (new record).
GenBank numbers – ITS = MW647877, LSU=MW647892.
Notes – Marasmiellus palmivorus is characterized by small to moderate-sized basidiomes with white or pink to orange striate, plano-convex pileus that fade to white with age and possess distant, occasionally intervenose white lamellae (Fig. 1). They also have a central to eccentric white stipe that becomes reddish orange to reddish brown at the base, ellipsoid basidiospores, clavate cheilocystidia with apical setulae, a cutis-type pileipellis of non-diverticulate hyphae, clavate and thin-walled caulocystidia. Marasmiellus palmivorus is similar to Collybia purpureogrisea, which was originally described as M. purpureogriseus. However, C. purpureogrisea differs by the presence of its non-striate pileus and has a longer stipe (up to 4 cm long). Basidiome is brownish-white, sub-close to crowded lamellae and displays the presence of a rameales structure in the pileipellis (Petch 1947; Manimohan and Leelavathy 1989). Phylogenetic analysis of the combined ITS and LSU regions indicates that our strain of M. palmivorus clusters with other strains in a strongly supported subclade (100% MLBS, 1.00 BYPP; Fig. 2).
Figure 1 – Marasmiellus palmivorus (SDBR-CMU-NK076, new record). a Basidiomata. b Basidiospores. c Basidia. d Cheilocystidia. e Caulocystidia. Scale bars: a=1 cm, b–e=10 μm
Figure 2 – Phylogenetic tree derived from maximum likelihood analysis of a combined ITS, and LSU genes of 22 sequences and the aligned dataset was comprised of 2070 characters including gaps (ITS: 1–1120 and LSU: 1121–2070). The average standard deviation of the split frequencies of the BI analysis was 0.00731. A best scoring RAxML tree was established with a final ML optimization likelihood value of − 10104.6944. The matrix had 806 distinct alignment patterns with 56.72% undetermined characters or gaps. Estimated base frequencies were found to be: A=0.2519, C=0.1827, G=0.2462, T=0.3193; substitution rates AC=1.0427, AG=3.9637, AT=1.7229, CG=0.7530, CT=4.8493, GT=1.0000; proportion of invariable sites=0.0510 and gamma distribution=0.4750. Gymnopus nebrevipes TFB14505 and Gynnopus pygmaeus URM90003 were used as outgroup. Numbers above branches are the bootstrap statistics percentages equal to or greater than 70% (MLBS, left) and Bayesian posterior probabilities equal to or greater than 0.95 (BYPP, right). Extype strains are in bold and newly generated sequence is in blue