Agaricus candussoi L.A. Parra, Angelini & Callac, 2018

Parra, Luis A., Angelini, Claudio, Ortiz-Santana, Beatriz, Mata, Gerardo, Billette, Christophe, Rojo, Carlos, Chen, Jie & Callac, Philippe, 2018, The genus Agaricus in the Caribbean. Nine new taxa mostly based on collections from the Dominican Republic, Phytotaxa 345 (3), pp. 219-271 : 255

Agaricus candussoi L.A. Parra, Angelini & Callac , sp. nov. ( Figs. 16–17 )

MycoBank: MB823282.

Etymology: The specific epithet “ candussoi ” honors our good friend and excellent mycologist, Massimo Candusso, for his contribution to Mycology.

Original description, Macroscopic description: Pileus 5–7 cm diam., hemispherical, then conical-trapezoid for a long time, later plano-convex slightly depressed at center, white with an entire grayish brown center, covered to margin with minute punctate scales, scarce, concentric, grayish at the peridiscal area and whitish to margin. Surface smooth or slightly squamulose, dry and dull. Margin thin, fimbriate, not or slightly exceeding the lamellae. Lamellae free, crowded, narrow, straight, intercalated with numerous lamellulae, at first pinkish cream, then bright pink, finally grayish pink brown with the edge paler and slightly eroded. Stipe 6–8(–9) × 0.5–0.8 cm, cylindrical with slightly bulbous base, long, thin, straight or curved, sometimes flexuose, stuffed, with an annulus in its upper third, above and below annulus smooth, slightly sericeous towards the base, white, unchangeable on handling, often with a basal rhizomorph. Annulus superous, double, white, up to 1.5 cm broad, thin at the insertion but thicker at the margin, upper surface slightly striate, lower surface with thick and arched scales that detach easily. Sometimes the thicker part of the margin is divided into two membranes, the upper one is fibrillose in its upperside and cottony in the lowerside, and the inferior membrane with smooth margin that forms a bracelet adpressed to the stipe. Context white when cut, unchanging or slightly yellowing at the basal part of the stipe in contact with the mycelium, with a strong odor of phenol.

Microscopic description: Spores 4.12–4.63–5.17 × 2.80–3.07–3.40 μm, Q=1.37–1.51–1.72, ellipsoid, smooth, brown, without apical pore. Basidia 15–20 × 5–8 μm, tetrasporic, clavate or slightly truncated at the apex, sterigmata up to 3 μm long. Cheilocystidia abundant, hyaline, simple, rarely with a basal septum, clavate, pyriform, ovoid or globose, rarely fusiform, 11–27 × 7.5–19 μm. Pleurocystidia not observed. Lower surface of the annulus hyphae 3–11 μm wide, hyaline, cylindrical, the wider the more constricted at septa. Inflated elements not observed. Pileipellis a cutis, hyphae 2–5 μm wide, not or slightly narrowed at septa, terminal elements very abundant cylindrical, rounded at apex, with yellow or pale brown internal granular pigment in water. Clamp connections not observed.

Macrochemical reactions: Schäffer’s reaction negative. KOH reaction positive, yellow with orange spots.

Habit, habitat, occurrence and distribution: Gregarious, sometimes in groups of many basidiomata, in moist lowland broadleaf forests. Rare. Recorded only from the Dominican Republic.

Species-specific ITS markers in A. sect. Xanthodermatei : aatctAtctcc@199, gttatCcattatactcCtataa@223–234, with C insertion at position 234.

Note: This species is characterized by its medium to large size, white pileus with an entire grayish brown center, typical complex annulus, the absence of yellowing on handling or if present is almost imperceptible, and the strong odor of phenol.

Material examined: DOMINICAN REPUBLIC, Puerto Plata, Sosúa, Puerto Chiquito , 28 November 2014, JBSD126490 ( LAPAM57 ) ; Puerto Plata, Sosúa, Puerto Chiquito , 3 December 2014, JBSD126491 ( LAPAM58 ) ; Puerto Plata, Sosúa, Puerto Chiquito , 13 December 2014, JBSD126492 Holotypus ( LAPAM62 Isotypus ) .

Taxonomic comments: The macroscopic description of collections of A. cretacellus Atkinson (1902: 110) sensu Pegler ( Pegler 1983) from Martinique corresponds well with A. candussoi . However, A. cretacellus sensu Pegler has larger spores (5–5.5–6.5 × 2.7–3.2–3.5[–4] μm) and lacks cheilocystidia. According to the original description of A. cretacellus ( Atkinson 1902) , this species has “odor and taste of almonds” and the lower surface of the annulus is covered by “very fine floccose scales similar to those of the stem” and therefore it most likely belongs to A. sect. Arvenses , whereas A. cretacellus sensu Pegler was described as having an “odor of iodine, disagreeable” and “glabrous” stipe, typical characteristics of A. sect. Xanthodermatei .

Figures

FIGURE 16. Macroscopic characters of A. candussoi. A–I. Basidiomata. A–B, G. (JBSD126490); C–D, H. (JBSD126491); E–F. I. (JBSD126492, holotype). Photos by C. Angelini.

FIGURE 17. Microscopic characters of A. candussoi. A–G. In ammoniacal Congo red. A–C. (JBSD126491), D. (JBSD126490), E–G. (JBSD126492, holotype).A–C. Cheilocystidia. D. Basidia. E. Spores. F. Hyphae of the lower surface of the annulus. G. Pileipellis hyphae. Photos by L.A. Parra.