Agaricus catenatus

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

Fungal Names: FN570355; Faceoffungi Number: FoF 02926

Pileus 50 mm in diam., plane; disc slightly truncated; margin straight with white appendiculate remains of universal veil; surface dry, fibrillose, appressed, white generally excepting light brown to reddish brown at disc; background white or light gray, turning red in wet. Context 3 mm thick at disc, flesh, white. Lamellae up to 3 mm broad, far free, crowded, pink brown to brown. Annulus single, fragile, membranous, white, pendant, smooth on both sides. Stipe 55 × 6 mm, hollow, white, cylindrical; surface dry, smooth above the annulus, fibrillose below the annulus. Odour of almonds. Basidiome no discoloration or slightly flavescent when touching. Discoloration yellowish brown after several minutes on cutting. KOH reaction: positive yellow. Schäffer’s reaction: positive, reddish orange on dry specimen. Basidiospores 4.6–5.4 × 2.7–3.5 μm, [x = 5.1 ± 0.2 × 2.7 ± 0.1, Q = 1.4–1.8, Qm = 1.4 ± 0.1, n = 20], ellipsoid, elongate, smooth, thick-walled, brown. Basidia 14.5–20.5 × 4.5–7.7 μm, long clavate, hyaline, 4-spored, smooth. Cheilocystidia 13.3–33.7 × 10.8–18.3 μm, mostly catenulate by 2–3 elements of clavate, globose or ellipsoid, smooth, hyaline, some with yellow pigments inside. Pleurocystidia absent. Pileipellis a cutis composed of hyphae of 3.3–11 μm in diam., smooth, cylindrical, yellowish brown, no constricted at septa.

Habitat: solitary in forest.

Notes: In phylogeny analysis, this new species is sister to A. jingningensis under the support of 0.9/- PP/BS values in clade IX. The morphological difference between them are presented in A. jingningensis part. Generally, this new species is characterized by its nearly white pileus and the catenulate cheilocystidia, and the latter is rare for the species of section Minores.

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.