Agaricus moelleri Wasser

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 : 188-189

Agaricus moelleri Wasser , Nov. sist. Niz. Rast. 13: 77 (1976)

MycoBank MB308356

Description based on four Iranian samples

Macroscopic characters:––Pileus 4–10(–16) cm in diam., 7–14(–17) mm thick, at first hemispherical or conictruncate and finally applanate or slightly umbonate at disc; surface covered with grey or dark to blackish appressed fibrillose squamules, more dense toward the discwhich is almost back; margin thin, entire, not or shortly exceeding the lamellae. Lamellae free, crowded, with lamellulae, at first persistently whitish then pink, with age brownish and finally dark brown to black. Stipe 4–8(–16) × 1–1.7 cm (2–2.6 cm at the bulbous base), central, hollow, clavate, slightly bulbous or abruptly bulbous, white, surface smooth, becoming yellow on bruising then taking an orange-ochre color with time, base often with mycelial strand or with fragile rhizoids. Annulus superous bilayered, membranous, smooth, white but yellowing with time or on bruising; the lower layer broke in a cogwheel decorating the lower surface. Context white, then slightly yellowish by cutting. Odor of phenol or iodine on cutting ( Fig.4 ).

Microscopic characters:––Basidiospores (4–)4.5–6.9(–6.9) × 2.8–4.8 μm, [5.37 ± 0.35 × 3.56 ± 0.23, Q = 1.13–1.92, Qm = 1.52 ± 0.11, n = 30], usually ellipsoid to oblong, less frequently broadly ellipsoid, smooth, brown. Basidia 15–22 × 5–7 μm, clavate or barely truncate at the apex, hyaline, 4-spored, with sterigmates up to 3 μm long. Cheilocystidia present, but sometimes difficult to observe because coalescing into bunches enveloped in a mucilaginous substance, hyaline or with brown content, clavate, pyriform, globose or sphaeropedunculate, simple or less frequently, with a septum in the pedicel, 13–24 × 6–18 μm. Pileipellis a cutis composed of hyphae of 6–10 μm diam., light brown, smooth, slightly constricted at the septa ( Fig. 5 ).

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

Habit, habitat and distribution:––Solitary or in small groups of basidiomata, generally in wooded areas, under broad-leaf trees. A species which may be locally abundant, widely distributed throughout the north of Iran.

Specimen examined: –– IRAN, Guilan province, Rezvanshahr & Shanderman, 28 August 1987, leg. A. Karavar, M. R. Delghandi & H. Tehrani, ( IRAN 7327 F) ; Mazandaran province, Chalus, Namakabrood , 8 September 1991, leg. M. Saber & A. Alavi, ( IRAN 9397 F) ; Mazandaran province, Nowshahr, Kheiroodkenar, 14 October 2005, leg. M. Bahram ( IRAN 12461 F), Golestan province, Alangdareh forest , solitary, on leaf litter under tree, 607m, N36.45302, E54.29056, 16 October 2013, leg. V. Mahdizadeh, VM 029 ( IRAN 16701 F, TMU029 ) ; IRAN, Guilan province, Siahkal forest , solitary,on leaf litter under tree, 105m, N37.38655, E48.57915, 25 October 2014, leg. V. Mahdizadeh, VM 099 ( IRAN 16702 F, TMU099 ) ; IRAN, Mazandaran province, Behshahr, Abbas Abad forest , solitary,on leaf litter under tree, 438m, N36.39203, E53.35808, 10 November 2014, leg. V. Mahdizadeh, VM 112 ( IRAN 16703 F, TMU112 ) .

Notes:–– Agaricus moelleri and A. xanthodermus are closely related species that consistently differ from each other at least at the positions 139 and 206 of their rDNA ITS1 regions. At these positions A. moelleri has nucleotides C and T (gctctCgctgg@139; tttccTgtcag@206) while A. xanthodermus has T and C respectively (gctctTgctgg@139; tttccCgtcag@206). These molecular differences were consistently correlated with the presence or absence of colored persistent squames in A. moelleri and A. xanthodermus , respectively ( Kerrigan et al. 2005). This was also the case for the specimens presently reported from Iran. When the morphological characters are doubtful for different reasons (old specimens, dry conditions etc.), ITS sequences can be used to distinguish between the two species.

Parra (2013) noted that some specimens have wider spores than those generally reported in literature as for example LAPAG 587 (6.1 × 4.2 μm on average). The specimen IRAN 7327 F has such larger mean basidiospore sizes (5.56 ± 0.56 × 4.15 ± 0.30 μm) while the other examined specimens including the herbarium specimen IRAN 9397 F have smaller basidiospore ( Table 2).

Figures

FIGURE 4. Agaricus moelleri. A: VM029, B: VM099, C: KOH reaction on VM112.Bars: 1cm.

FIGURE 5. Agaricus moelleri. A: basidiospore of VM029, B and D: Cheilocystidia of VM029, C: Pileipellis of VM029, Bars: 10 μm.