Agaricales » ‎Agaricaceae » Agaricus

Agaricus dilatostipe

Agaricus dilatostipes M.Q. He & R.L. Zhao

Fungal Names: FN570354; Faceoffungi Number: FoF 02927

Pileus 44–110 mm in diam., parabolic first, then convex, finally plane; disc slightly unbonate; margin straight, exceeding; surface dry, with plenty of fibrils covered whole cap; background white or light brown, turn into red when water-soaked; fibrillose scales reddish brown, triangular, appressed, denser on disc, scanty towards the margin. Context 4–6 mm thick, flesh, white. Lamellae 4–6 mm broad, far free, crowded, pink first, then brown, edge even, intercalated with lamellulae. Annulus 10–30 mm in diam., single, white, fragile, membranous, pendant, smooth on both sides. Stipe 90–150 × 4–10 mm (6–30 mm at base), white, hollow, cylindrical, bulbous at base, surface dry, silky, slightly fibrillose. Odor of almonds. Basidiome flavescent first when touching and bruising, then turn into orange after few minutes. Yellowish on cutting. KOH reaction: positive yellow. Schäffer’s reaction: positive, reddish orange on dry specimen. Basidiospores 4.5–5.6 × 3.0–3.5 μm, [x = 5.1 ± 0.3 × 3.3 ± 0.2, Q = 1.4–1.8, Qm = 1.6 ± 0.1, n = 20], ellipsoid, elongate, smooth, thick-walled, brown. Basidia 13.8–25.8 × 5.1–7.6 μm, clavate, hyaline, 4-spored, smooth. Cheilocystidia 15–40 (−65) × 9.0–20 μm, smooth, simple, clavate most, can be broadly clavate and capitate with long narrow stipe, hyaline. Pleurocystidia absent. Pileipellis a cutis composed of hyphae of 3.5–9.9 μm in diam., smooth, cylindrical, brown, slightly constricted at septa.

Habitat: solitary or scattered on soil in forest.

Other specimens examined: Tacheng, Weixi County, Yunnan Prov., China, collected by Xu Meng-Lin, ZRL2014450 (HMAS275758). Dazhongshan Forestry Factory, Nanhua, Yunnan Prov., China, 11 September 2015, collected by Zhou-Junliang, ZRL20151110 (HMAS275762).

Notes: In phylogeny analysis, A. dilatostipes is sister to A. blatteus under the support of 1.0/91 PP/BS values. In the morphology, A. blatteus has a small cap (diam. 13–28 mm), while A. dilatostipes is middle to large sized in pileus (pileus 44–110 mm diam.). Another distinct morphological character of A. dilatostipes is its bulbous base at the stipe, which is similar to those of A. dulcidulus Schulzer, A. jacobi L.A. Parra, A. Caball. & Callac, A. matrum L.A. Parra, A. caball., S. Serrano, E. Fernández & Callac and A. purpurellus 4. However, the basidiospores of A. dulcidulus is smaller (3.6–4.8 × 2.6–3.3 μm) than those of A. dilatostipes; the cheilocystidia of A. jacobi is multiseptate, which is different from A. dilatostipes; A. matrum and A. purpurellus have much smaller basidiome (pileus 15–50 mm in diam.) than those of A. dilatostipes 4. Then we proposed A. dilatostipes as a new species. This new species is distinguished by its large basidiome, obviously bulbous base of stipe and simple cheilocystidia.

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.