Agaricus gratolens Pradeep & R.L. Zhao
Index Fungorum number: IF 570207; Facesoffungi number: FoF 01206
Pileus 40–45 mm in diam., 2 mm thick at disc, convex with truncate top, margin exceeding; surface dry, with fibrillose scales, light brown, dense at the disc, background cream to light greyish white. Lamellae free, crowded, intercalated with lamellulae, 3 mm broad, firstly white, light brown, then brown, finally dark brown. Stipe 75 × 5 mm, cylindrical, curved, with short rhizomorphs, white, smooth above the annulus, with fibrillose to fibrillose scales below the annulus, staining weakly yellow on touching. Annulus membranous, pendent, simple, superous, fugacious, torn, stretched, white, up to 7 mm broad, low side floccose. Context firm, on cutting white, both in pileus and stipe, then quickly turning slightly ochraceus at the centre of pileus. Odour of almonds. Macrochemical reaction: KOH and Schäffer’s reactions negative.
Basidiospores 5–6×3–4 μm [x = 5.6 ± 0.4× 3.5 ± 0.3, Q=1.4–1.9, Qm = 1.63 ± 0.27, n = 20], ellipsoid, reddish brown, smooth, thick-walled, without germ pore. Basidia12–14× 5–7 μm, clavate, smooth, hyaline, 4-spored. Cheilocystidia10–18× 6–8 μm, broad clavate, ellipsoid, some pyriform, hyaline, smooth. Pleurocystidia absent. Pileipellis a cutis consisted of hyphae 5–8 μm in diam., long cylindrical, with dark grey pigment distributed unevenly, smooth. Annulus hyphae of elements 5–10 μm in diam., ellipsoid, cylindrical, hyaline, smooth. Stipitipellis hyphae similar to those of annulus. (Fig. 2–3)
Habitat: scattered in rich soil of forests.
Material examined: I THAILAND, Chiang Mai Prov., Mae Taeng Dist., Hot Spring, 8 August 2006, collected by Ohnmar Myo Aung, ZRL3093 (BBH19609, holotype; HMAS274011, isotype). NDIA, Kerala State, Trivandrum District, Perayam, 30 Aug. 2006, No. 9679(P) CA956 (=PYP012).
Notes: this new species is similar to A. kivuensis in pileus, basidiospores, and cheilocystidia characteristics. However, the new species has a white stipe surface and stains yellow on touching, while the stipe of A. kivuensis is brown and stains rose. The phylogenetic analysis also supports them as distinct species.
Fig. 1 Phylogeny of Agaricus subgenus Spissicaules generated from Bayesian analysis of ITS sequences, rooted with A. campestris. Bootstrap support (BS) values > 50 % and Bayesian posterior probability (PP) values > 80 % (or >50% in some main clades) are given at the internodes (PP/BS). BT^ means the sequence is from type specimen; a clade with thick branch is corresponding a certain section in Fig. 1