Pleurotus giganteus (Berk.) Karun. & K.D. Hyde
Index Fungorum number 561087, FacesofFungi number: FoF 01761
Pilei 40–310 mm in diam., convex to applanate dark brown (7F4) towards margin, reddish grey in the margin (12D3), fibrillose-scaly at the centre, at first uniformly dark at the surface, fuscous brown and black, then fading with age to yellowish brown (E9), with a darker centre, remaining dark, dry, disrupted into small, indefinite, radial, innate squamules, overlaid by scanty, pale grey or blackish, verrucose-floccose, with concentrically arranged remnants of the veil; margin strongly involute, thin. Lamellae moderately crowded with lamellulae of five to six lengths, decurrent, 3–4 mm broad, white to cream (3A1); edge entire, pale ochraceous or yellowish-brown (E9). Stipe up to 40–200 mm long, 6–10 mm broad at the apex, 9–15 mm at the base, fusiform, with radicating base (50–70 mm long), solid, surface concolorous with the pileus, paler at the apex, finely tomentose with indefinite zones of paler velar remnants, in the early stages; veil thin, floccose, pale to dark brown (6F5), soon reduced to floccose remnants but never forming an annulus on the stipe. Context 4–10 mm thick at the disk, submembranous at the pileal margin, white in pileus and stipe, fleshy-spongy, consisting of a dimitic hyphal system with skeletal hyphae. Generative hyphae 3–6 μm in diameter, inflating with a thick or slightly thickened wall, more or less radially parallel, but frequently branching and with large clamp connections. Skeletal hyphae 5–8 μm in diameter, hyaline of intercalary or terminal origin, becoming very thick-walled with a narrow lumen, tending to taper apically, occasionally with a limited lateral branch.
Basidiospores 6–8.5 (–9) × 4.4–5.3 μm [n =60, Lm=7.65 μm, Wm=5.02 μm, Q=1.36–1.69, Qm=1.51], broadly ellipsoid to ellipsoid, white in mass, smooth, with one large oil drop or multiguttulate, inamyloid, thin-walled. The large basidiospores are not cylindrical but broadly ellipsoid, although the largest basidiospores become oblong ellipsoid. Basidia 28–50 × 8–9 μm, elongate, clavate, bearing 4 sterigmata. Lamella edge sterile with a broad layer of Cheilocystidia 23–36 × 6–10 μm, more or less lecythiform, with a ventricose base and a small capitellum (2–4 μm), subtended by a narrow neck, hyaline, thin-walled. (Figs 2–3)
Specimens examined: CHINA, Yunnan Province, Xishuangbanna, Mengsong Village; UTM-N2379744.485281, UTM-E653217.753714; alt. 1600m; 27 June 2014; on ground; Jie Chen (MFLU 14-0740); 15 June 2012; Samantha C. Karunarathna (MFLU 14-0741); Jiangxi Province; Fuzhou City; 6 February 2015; from JingShan mushroom growing company; Jinshan Fang (ZRL-2015001, HMAS-253762); SRI LANKA, Central Prov., Kandy Distr., Deliwala village, 7°14′43.55″N 80°33′51.40″E, elevation 1050 m, rainforest dominated by Swietenia spp. and Artocarpus heterophyllus, 5 June 2009; on ground; Samantha C. Karunarathna (MFLU 11-0018, epitype); THAILAND, Chiang Mai Prov., Mae Taeng Distr., Ban Pha Deng, Mushroom Research Centre, 19°17.123′N 98°44.009′E, elevation 900m, rainforest dominated by Castanopsis armata, Erythrina sp, and Dipterocarpus sp., 8 July 2008; on ground; Ruilin Zhao (MFLU 08-1370); 21 June 2008; on ground; Samantha C. Karunarathna (MFLU 10-0138); 27 June 2008; on ground; Samantha C. Karunarathna (MFLU 08-1371); 6 July 2008; on ground; Samantha C. Karunarathna (MFLU 08-1382); 22 July 2008; on ground; Samantha C. Karunarathna (MFLU 10-0137); 10 July 2010; on ground; Olivier Raspe (MFLU 10-0153); DoiSuthep-Pui National Park, Sangasabhasri Lane to HuaiKok Ma village, 18°48.62′N 98°54.60′E, elevation 1145 m, rainforest dominated by Castanopsis spp., Lithocarpus polistachyus and other trees, 9 June 2008; on ground; Samantha C. Karunarathna (MFLU 10-0136); Chiang Rai prov., Highway No.110 to Mae Sai, Doi Tung, 20°17′37″N 99°48′56″E, elevation 950 m. 15 July 2009; on ground; Samantha C. Karunarathna (MFLU 10-0140); 15 July 2009; on ground; Samantha C. Karunarathna (MFLU 10-0141); 8 August 2009; on ground; Samantha C. Karunarathna (MFLU 10-0142); 8 August 2009; on ground; Samantha C. Karunarathna (MFLU 10-0143); 16 July 2010, Samantha C. Karunarathna (MFLU 10-0154).
Habitat and distribution: on buried rotten wood in the rain forest, solitary. Widely distributed in Australia, China, Malay Peninsula, Sabah, Sri Lanka, Vietnam, and Thailand.
Fig 1. Phylogenetic tree showing the relationships between Pleurotus giganteus and Pl. tuberregium with some selected Lentinus, Panus and Pleurotus species based on ITS-1-5.8 S-ITS2 rDNA sequence data. Bootstrap support values for maximum parsimony are equal or higher than 50 % are defined as above the nodes and Bayesian posterior probabilities equal or higher than 0.95 are given below the nodes. Lentinus squarrosulus (AB478883) and Panus sp. (AB509648) are out group.
Fig. 2 Basidiocarps of Pleurotus giganteus A, B. Pleurotus giganteus from Mengsong, China (A. MFLU14-0741, B. MFLU14-0740) Scale bars: A, B = 10 cm.