Agaricus grandiomyces J.L. Zhou & R.L. Zhao, 2016

Zhou, Jun-Liang, Su, Sheng-Yu, Su, Hong-Yan, Wang, Bo, Callac, Philippe, Guinberteau, Jacques & Zhao, Rui-Lin, 2016, A description of eleven new species of Agaricus sections Xanthodermatei and Hondenses collected from Tibet and the surrounding areas, Phytotaxa 257 (2), pp. 99-121 : 106-110

Section Hondenses

1 Agaricus grandiomyces J.L. Zhou & R.L. Zhao , sp. nov. ( Fig. 4 : A–E)

MycoBank NO.: MB 812313

Diagnosis: this species is characterized by its triangular and curved brown to yellowish brown squamules on the cap, stiped rhizomorphs, bulbous base, and ellipsoid basidiospores (5.7–6.5 × 3.8–4.4 μm).

Etymology: the word “grandiomyces ” refers to large basidiomata; from ‘grandis’ (Latin) large.

Material examined: China, Tibet, Milin County, Nanyigou Forest Park, N 29°07′45″, E 94°13′10″, elevation 3003.51 m, 29 July 2012, Xin-Yu Dong (ZRL2012611, HMAS 275728, HOLOTYPE).

Pileus 84 mm in diam., convex; surface covered by squamules, scales sharp triangular, slightly recurved, brown (oac640) at the disc, but fade into yellowish brown (oac683) towards the margin, background white; margin a little incurved and sterile overhang. Context 7 mm thick at the disc, white and fleshy. Lamellae free and crowded; with 3 series of plural-lamellulae, 8 mm broad broad, slightly ventricose, and dark brown; edge entire. Stipe 11 mm (apex)– 19 mm (base) × 180 mm (length); cylindrical with a bulbous base and rhizomorphs; surface smooth and silky above annulus, and covered with white fibrils below annulus; hollow. Annulus single, membranous, 10 mm in diam., superior, pendant-shaped; upper side white and smooth, lower side white with a yellow tone (oac 676) at the edge. Odor not iodine-like, but pleasant. Changing to yellow after bruising occurs on the stipe surface.

Macrochemical reactions KOH reaction yellow. Schäffer’s reaction negative.

Basidiospores ( Fig. 4–D ) (5.3–)5.7–6.5 × (–3.5)3.8–4.4 μm [x = 6.0 ± 0.3 × 4.0 ± 0.2 μm, Q = 1.4–1.6, Qm = 1.5 ± 0.1, n = 20 basidiospores]; ellipsoid, few broadly ellipsoid; smooth, thick-walled; light brown when young and brown when mature. Basidia are 16.7–17.4 × 4.5–5.8 μm, hyaline, smooth, clavate, and 4-spored. Cheilocystidia are not observed. Pleurocystidia absent. Pileipellis ( Fig. 4-E ) a cutis composed of hyphae 3.2–7.1 μm wide; smooth, not constricted at the septa; containing brown vacuolar pigments.

Habitat solitary under Picea trees.

Notes: This species, along with A. pusillobulbosus (see the next species in this article), A. freirei , A. hondensis , and A. phaeolepidotus , form the Hondenses section in the phylogenetic tree ( Fig. 1 ). Agaricus pusillobulbosus and A. hondensis are easily separated from the new species as they lack dark scales on their pileus ( Kerrigan 1986). Agaricus phaeolepidotus has a similar cap, but has cheilocystidia and an annulus with a collar-like ridge on the lower side ( Cappelli 1984). Agaricus freirei in this clade also has brown scales on the cap; however, its strong iodine smell, larger basidiospores and cheilocystidia allow it to be distinguished from the new species ( Blanco-Dios 2001; Guinberteau 2009). Agaricus bukavuensis Heinem. & Gooss. -Font. was first collected in the Congo ( Heinemann & Goossens-Fontana 1956). It has medium to large fruiting bodies and large scales on the pileus. However, it differs from A. grandiomyces in that it has wider basidiospores and a rough and subperonate annulus. Agaricus rosoeocingulatus has an almond smell, but has cheilocystidia and a reddish brown cap ( Heinemann 1978).

2 Agaricus pusillobulbosus S.Y. Su & R.L. Zhao , sp. nov. ( Fig. 5 : K–M)

MycoBank NO.: MB 812318

Diagnosis: this species can be recognized by its small basidiomata, medium grayish white cap, super superior and fragile annulus, stipe with a bulbous base, and broadly ellipsoid to ellipsoid basidiospores (5.1–5.9 × 3.5–4.4 μm).

Etymology: the word “pusillobulbosus ” refers to the small basidiomata and bulbose base; from ‘pusillus’ (Latin) small, and ‘bulbus’ (Latin) bulb.

Material examined: China, Tibet, Linzhi county, Bayi town, Cypress King Garden, N 29°37′21″, E 94°24′07″, elevation 3059.32 m, 31 July 2012, Sheng-Yu Su (ZRL2012627, HMAS 275732, HOLOTYPE).

Pileus 44 mm in diam. plane with a subumbonate centre; surface grayish white (oac907), dry, and covered with fine fibrils, light grey (oac905); centre light brown (oac850); margin split and straight. Context 5 mm thick at the disc, white and fleshy. Lamellae free and crowded; appearing as 5 series of plural-lamellulae, 3 mm broad, dark brown; edge entire. Stipe 9 mm (apex)– 14 mm (base) × 68 mm (length); cylindrical with a bulbous base; surface is white, smooth and silky, narrow; hollow. Annulus single, membranous, white, and located at the apex of stipe (super superior); split and covers the lamellae, and smooth at the upper and lower sides. Odor not iodine-like, but pleasant. Changing to slightly yellow upon touching and cutting the stipe.

Macrochemical reactions KOH reaction yellow. Schäffer’s reaction negative.

Basidiospores ( Fig. 5-M ) 5.1–5.9 (6.9) × (3.1) 3.5–4.4 (5.1) μm [x = 5.5 ± 0.3 × 4.0 ± 0.2 μm, Q = 1.2–1.6, Qm = 1.4 ± 0.1, n = 20 basidiospores], broadly ellipsoid to ellipsoid, occasionally elongated, smooth, thick-walled, and brown. Basidia 20.0–22.5 × 5.8–7.1 μm, hyaline, smooth, clavate, and 4-spored. Cheilocystidia are not observed. Pleurocystidia likewise absent. Pileipellis a cutis composed of hyphae 3.9–7.1 μm in diam; long cylindrical, smooth, and hyaline, and some constricted at the septa.

Habitat solitary in Cypress forests.

Notes: This species is a small mushroom with a grayish white cap, no squamules, a bulbous stipe, a thin and superior annulus and wide basidiospores. Agaricus freirei and A. hondensis are phylogenetically close to this new species. However, A. freirei has dark colored scales and much narrower basidiospores ( Blanco-Dios 2001; Guinberteau 2009). In contrast, A. hondensis is more similar to A. pusillobulbosus , as both have a light cap and a bulbous stipe; however, the former has much larger basidiomata, a tough and thick annulus, and ellipsoid to elongate basidiospores, all of which can be used to distinguish it ( Kerrigan 1986).

Figures

FIGURE 1. Phylogenesis of Agaricus generated from MrBayesian analysis of the ITS sequences, rooted with A. campestris. Bootstrap values (BS>50) and Bayesian posterior probabilities (PP>0.8) are given at the internodes.

FIGURE 4. A–E. Morphology A.grandiomyces (ZRL2012611, HOLOTYPE):A–C.Basidiomata;D. Basidiospores; E. Pileipellis hyphae. F–K. Morphology of A. gregariomyces (ZRL2012624, HOLOTYPE):F. Basidiospores; G,I–K. Basidiomata, J shows the yellowing staining on the pileus, K shows annulus characters; H. Pileipellis hyphae. Scale bar A–C,G, I–K = 10 mm; D–F = 10 μm; H = 5 μm.

FIGURE 5.A–G.Morphology of A.karstomyces(ZRL2011048, HOLOTYPE):A–C.Basidiomata;D.Basidiospores;E–G.Cheilocystidia. H–J. Morphology of A. malangelus (ZRL2012628): H–I. Basidiomata; J. Basidiospores. K–M. Morphology of A. pusillobulbosus (ZRL2012627, HOLOTYPE): K–L. Basidiomata; M. Basidiospores. Scale bar A–C, H–I, and K–L = 10 mm; D–G and J = 10 μm; M = 20 μm.