Agaricus iodosmus Heinem., Bull.

Mahdizadeh, Valiollah, Safaie, Naser, Goltapeh, Ebrahim Mohammadi, Asef, Mohammad Reza, Hosseini, Sayed Mohsen Nassaj & Callac, Philippe, 2016, Agaricus section Xanthodermatei in Iran, Phytotaxa 247 (3), pp. 181-196 : 186-187

Agaricus iodosmus Heinem., Bull. trimest. Soc. mycol. Fr. 81(3): 399 (1965)

MycoBank MB325896

Description based on the Iranian specimen VM080 (two mature and one young spococarps):

Macroscopic characters:––Pileus 5–13 cm in diam., 7–9 mm thick, at first globose, then convex with applanate center and finally applanate, white with uniformly light grey to sooty grey or greyish-brown color pigment at the center; surface smooth, dull and dry finally cracked by dryness; margin thin, entire, not or shortly exceeding the lamellae. Lamellae free, up to 1 cm broad, crowded, with lamellulae, at first persistently whitish, then light pink, later reddishbrown and finally of a dark brown almost black color. Stipe 44–70 × 17–24 mm, central, firm, occasionally pithy or fistulose, cylindrical, fusiform, clavate, less frequently slightly bulbous, smooth, glabrous and shiny, white, but turning deep chrome yellow when rubbed at the base. Annulus complex, superous, membranous, smooth on its lower side and appressed to the stipe, exhibiting a thick margin with three staggered unbroken rims, white but yellowing with time or on bruising. Context white at first, turning chrome yellow in stipe base. Odor phenolic or of iodine, stronger in stipe base when cut ( Fig. 2 ).

Microscopic characters:–– Two types of basidiospores: smaller type (about 94–95% of the basidiospores) 5.4– 6.4(–7) × 4.1–5.1(–5.5) μm, [5.84 ± 0.36 × 4.56 ± 0.28, Q = 1.2–1.49, Qm = 1.28 ± 0.06], n = 30], subglobose to broadly ellipsoid, less frequently ellipsoid, brown, larger type (5–6% of the spores) 5.3–9.5(–10.1) × 4.4–6.6, [7.83 ± 1 × 5.52 ± 0.59, Q = 1.16–1.7, Qm = 1.42 ± 0.16, n = 30], broadly ellipsoid, brown. Basidia 11.73–18.8–25.87 × 6.62– 7.15–7.68 μm, 4-spored, clavate or slightly truncate at the apex, with sterigmata up to 3 μm long. Cheilocystidia present, sometimes difficult to observe due to coalescing in an enveloping mucilaginous substance, hyaline or with brown content, usually simple or uniseptate, generally pyriform to clavate, 13.73–19.62–25.5 × 6.91–7.98–9.06 μm. Pileipellis a cutis of hyphae of 5.08–6.24–7.4 μm diam., slightly constricted at septa ( Fig. 3 ).

Chemical reactions:––KOH positive; Schäffer’s reaction negative.

Habit, habitat and distribution:––found in a single group of three scattered sporocarps, on ground anthropically strongly disturbed, close to a tree, on the sidewalk of a boulevard in city center.

Material examined:–– IRAN, East Azerbaijan province, Maragheh, N37.23030, E46.13258, 1428 m, 03 May 2014, leg. V. Mahdizadeh, VM080 ( IRAN 16700 F, TMU080).

Notes:–– Agaricus iodosmus is characterized by its robust pileus, a strong chrome-yellow discoloration when rubbed, and a superous annulus appressed to the stipe and exhibiting three edges and a smooth lower face. Microscopically this species has two types of cheilocystidia, one simple and claviform, the other multiseptate and very conspicuous, often with refractive walls, their proportion being highly variable. In the Iranian collection VM080 we did not observed such multiseptate refractive cystidia but only simple or uniseptate hyaline cheilocystidia as this has been also reported in certain specimens of this species ( Parra 2013).

According to Parra (2013) spore size of this species is 5.3–6.1–7 × 4.3–4.9–5.5(–6) μm, Q =1.08–1.26–1.5. In the Iranian collection, two different sizes of spores were observed possibly because of dryness occurring during sporogenesis which is known to be asynchronous in Agaricus . The smaller type of spores (5.8 × 4.5 μm) agreed with the spore size of the original diagnosis of this species (5.5–6.7 × 4.8–5 μm), while the larger type (7.8 × 5.5 μm) was significantly larger than all the spore sizes reported in literature and should result from an unknown biological phenomenon.

Figures

FIGURE 2. Agaricus iodosmus. A: VM080, B: yellowing with Bruising, C: KOH reaction, D: cross-section of the pileus. Bars: 1cm.

FIGURE 3. Agaricus iodosmus. VM080: A and B: different-sized spores, C, D: Cheilocystidia, E: Pileipellis, F: Probasidia and basidia, Bars: 10 μm.