Agaricus xanthodermus Genev., Bull. Soc.

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 : 191-193

Agaricus xanthodermus Genev., Bull. Soc. bot. Fr. 23: 28 (1876)

MycoBank MB155072

Description based on two Iranian specimens Macroscopic description: –– Pileus 6–11 cm diam., at first ovoid, campanulate, truncate-conical, then convex and finally applanate or broadly umbonate at center, margin thin, entire; Pileus surface smooth, white when young, with age greyish or light brown or cream or yellowish. Lamellae free, crowded, with lamellulae, 6–9 mm broad, at first whitish, then pink to brown, finally dark brown to black. Stipe 5.6–7.5 × 0.9–1.1 cm, central, fistulose, equal or slightly bulbous, smooth, glabrous, white, with an apical annulus. Annulus superous, two layered, membranous, up to 2 cm broad. Lower surface shows scales arranged into a cogwheel ( Fig. 6 ). Context white at first, changing to transient yellow or chrome yellow. Odor phenolic.

Microscopic description:––Basidiospores(4.7–)4.9–6(–6.8) × 3.3–4(–4.3)μm, [5.4 ± 0.26 × 3.7 ± 0.19, Q =1.33– 1.68, Qm= 1.47 ± 0.1 μm, n = 30], usually broadly ellipsoid to ellipsoid, rarely subglobose or oblong, brown. Basidia 13.9–22.9 (–24.6) × 6.1–7.2 μm, 4-spored, clavate or slightly truncate at the apex, hyaline, smooth. Cheilocystidia present, globose, clavate, pyriform, usually simple, occasionally with one septum in the pedicel, hyaline, smooth, 11.6–28.8 × 8.1–19.3 (–20.7) μm. Pileipellis a cutis composed of hyphae of 6.5–8.9 μm diam., cylindrical, slightly constricted at the septa ( Fig. 7 ).

Chemical reactions:––Schaffer’s reaction negative, KOH reaction positive.

Habit, habitat and distribution:––Solitary, on leaf litter or in grass.

Specimen examined: –– IRAN, Guilan province, Kiashahr , under cypress close to Caspian sea coast, solitary on litter and moss ( Fig. 6 ), - 11m, N37.24627, E50.01167, 3 December 2013, leg. V. Mahdizadeh VM 043 ( IRAN 17007 F, TMU043 ) ; Golestan province, Golestan forest, solitary, on grass in a sparse open forest, 488m, N37.23378, E55.48371, 8 November 2014, leg. V. Mahdizadeh, VM 101 ( IRAN 17006 F, TMU101 ) .

Notes:–– Agaricus xanthodermus , which can grow in various types of habitat, is nitrophilous and thus is more frequent in amended grass and other anthropized areas. Our specimen of A. xanthodermus , represents in fact the true first report of this species from Iran since the ITS sequence of the herbarium sample of the single previous report of this species does not agree with A. xanthodermus but is similar to sequences of A. bitorquis . The comparison with the sister species A. moelleri is reported above in the note of the latter.

Figures

FIGURE 6. Agaricus xanthodermus. A: VM101, B: Cap surface of VM101, C: KOH reaction of VM101, D: Yellowing with bruising of VM101, E: Yellowing with bruising of VM043, D: VM043 in moss under cypress. Bars: 1cm.

FIGURE 7. Agaricus xanthodermus. VM101: A: basidiospore, B, C and D: Cheilocystidia, E: Pileipellis, Bars: 10 μm.