Agaricus minorpurpureus M.Q. He & R.L. Zhao
Fungal Names: FN570349; Faceoffungi Number: FoF 02925
Pileus 16–18 mm in diam., plane, convex; disc slightly unbonate; margin straight, exceeding; surface dry, covered by fibrils at the whole cap; background white, turn into purple red in wet; fibrils reddish brown or purplish brown, forming fibrillose scales at disc, and fading towards the margin. Context 1 mm thick, flesh, white. Lamellae 2–3 mm broad, far free, crowded, pink or pinkish brown first, then brown in age, edge even, ventricose, intercalated with lamellulae. Annulus 2–3 mm in diam., single, fragile, membranous, pendant, white. Stipe 12–40 × 2 (4–5 at base) mm, white, hollow, cylindrical, bulbous at base with rhizomorphs, surface dry, silky, fibrillose below the annulus. Odour of almonds. Basidiome flavescent when touching, no discoloration on cutting. KOH reaction: positive yellow; Schäffer’s reaction: positive, reddish orange on dry specimen. Basidiospores 4.7–5.3 × 2.9–3.7 μm, [x = 5.0 ± 0.2 × 3.3 ± 0.2, Q = 1.4–1.6, Qm = 1.5 ± 0.1, n = 20], ellipsoid, smooth, thick-walled, brown. Basidia 13.3–19.5 × 5.3–6.9 μm, clavate, hyaline, 4-spored, smooth. Cheilocystidia 21–45 × 6–11.6 μm, abundant, clavate, smooth, hyaline with yellow pigments inside. Pleurocystidia absent. Pileipellis a cutis composed of hyphae of 2.2–7.6 μm in diam., smooth, cylindrical, brown, slightly constricted at septa.
Habitat: solitary on soil in forest.
Other specimens examined: Tongbiguang, Yingjiang County, Yunnan Prov., China, 20 July 2013, collected by He Mao-Qiang ZRL2013342 (HMAS275759).
Notes: In our phylogenetic analysis, A. minorpurpureus are represented by specimens ZRL2010058 and ZRL2013342. This two specimens form a distinct clade with the support of 1.0/100 PP/BS values in clade XIII (Figs 1–2). Agaricus minorpurpureus is a species with tiny basidiome (pileus diam. less than 20 mm), and several species of section Minores has such small basidiome, such as A. callacii L.A. Parra, R. Iglesias, Fern.-Vic. & Oyarzabal and A. parvibicolor. But A. callacii has larger basidiospores (5.7–6.7 × 4.2–5.36 μm) and dark brown scales on the pileus4, which are different from those of A. minorpurpureus. Also, only present clavate cheilocystidia makes A. minorpurpureus differ from A. parvibicolor and A. gemloides M.Q. He & R.L. Zhao5. The cheilocystidia of A. parvibicolor and A. gemloides are pyriform, globose or capitate with long stipe19. Considering the distinct morphological features, such as its extremely small basidiome, purplish brown scales, abundant of clavate cheilocystidia, and distinct phylogenetic position of A. minorpurpureus, we proposed it is new to science.
Fig. 1 Maximum Likelihood (ML) tree of Agaricus section Minores based on LSU, tef1-α, rpb2 and ITS sequences with the outgroup Agaricus campestris. The Bayesian posterior probabilities and bootstrap support values more than 0.9/50% (PP/BS) are indicated at the nodes. The branches in Bold mean the related PP > 0.95. Sequences produced from this study are in blue. “T” refers to sequences from type specimen, and “T” in red refers to the sequences from type specimen and new to science from this study.