Agaricus sinodeliciosus Z.R. Wang & R.L. Zhao, 2015

Wang, Zhuo-Ren, Callac, Philippe, Zhou, Jun-Liang, Fu, Wen-Jin, Dui, San-Han & Zhao, Rui-Lin, 2015, Edible species of Agaricus (Agaricaceae) from Xinjiang Province (Western China), Phytotaxa 202 (3), pp. 185-197 : 192-194

Agaricus sinodeliciosus Z.R. Wang & R.L. Zhao , spec. nov. (Figure 2: I–L; Figure 5)

MycoBank: MB 810516

Typus:— CHINA, Xinjiang Province, Bortala, Ebinur Lake , 10 May 2012, WZR2012 821, collected by Zhuo-Ren Wang (holotypus HMAS!; isotypus SWFC!)

Basidiomata medium to large, growing underground (in sandy soil) and buried, when young, then erumpent, semihypogeous. Pileus 70–120 mm in diameter when mature, and around 50 mm in diameter when young, cushionshaped, then complex, truncate or shallowly depressed at disc, margin involute; surface covered with appressed, fine light brown or buff brown squamules on a dirty white background, reddish-brown when bruised. Lamellae free, crowded, very narrow, reddish-brown, then brown, finally dark brown, with several series of lamellulae. Stipe 80–100 × 70–80 mm when mature, and 60 × 30 mm in young basidiomata, stout, first broadly fusiform with a rounded base, then cylindrical with a tapering base with age. Annulus inferous forming a volviform, peronate, membranous, broad sheath, with a narrow annular ledge in its centre, derived from the universal veil, remnants often remain appressed to stipe surface, yellowish-brown, but sometimes completely falling off, showing the smooth or fibrillose, white stipe surface which becomes reddish-brown when bruised. Context firm, dirty white, reddish-brown on cutting.

Macrochemical reactions: KOH negative; Schäffer reaction negative.

Basidiospores very variable in size and shape, 6.4–8.3 (–9) × 4.9–6.4 μm, avX = 7.2 ± 0.6 × 5.7 ± 0.5 μm, Q = 1.2–1.5, avQ = 1.27, n = 20, subsphaerical to broadly ellipsoid, smooth, thick-walled, brown, without apical pore. Basidia very rare, or even absent in a basidiomata, 13–17 × 4–7 μm, clavate, 4-spored, hyaline, with sterigmata up to 2 μm long. Cheilocystidia 20–41 × 6–10 μm, globose, clavate or broadly clavate, often with a long peduncule, hyaline or with yellowish-brown vacuolar pigment. Pleurocystidia similar to the cheilocystidia, some with rudimentary sterigmata at apex. Pileipellis a cutis composed of hyphae 4–16 μm wide, cylindrical, branched, curved, the broader the more constricted at septa, with light brown parietal pigment. Terminal elements abundant, 4–7 μm wide with attenuate apex. Annulus composed of cells 5–10 μm wide, hyaline, cylindrical, or elongate ellipsoid.

Diagnosis:—This species is distinguished by its medium to large semihypogeous basidiomata, light colored pileus, large spores and presence of pleurocystidia.

Habit, habitat and distribution:—solitary or gregarious, in sandy soil of reedy grassland. Only known from China, but probably distributed in Russia.

Etymology:—the epithet “sino” means origin from China; epithet “deliciosus” means this species is edible and tasty.

Other materials examined:— CHINA, Xinjiang Province, Bortala, Ebinur Lake, 2011, WZRxinjiang1, ibidem, 10 May 2012, WZR2012 8210, WZR2012 822, WZR2012 823, WZR2012 824, WZR2012 902, WZR2012 905, WZR2012 906, all collected by Zhuo-Ren Wang. All samples deposited in SWFC! and HMAS!.

Notes:— Agaricus sinodeliciosus belongs to Agaricus [section Bivelares ] subsection Hortenses . The most similar species to A. sinodeliciosus is A. subsubensis Kerrigan , but the latter differs in its much smaller basidiospores (6.2– 6.6 × 5.3–5.6 μm) and absence of cheilocystidia and pleurocystidia ( Kerrigan et al. 2008). Agaricus balchaschensis Samgina & Nam also has medium to large semihypogeous basidiomata, however, it also differs from A. sinodeliciosus in lacking cheilocystidia and pleurocystidia ( Samgina & Nam 1989). There is no available ITS sequence from the type specimen of A. balchaschensis . We contacted the AA herbarium where the type material is deposited and also one of the authors (G.A. Nam) to request type material on loan without success. In GenBank the sequence AM930983 of “ Agaricus sp. 1331” deposited by Hildén in 2013 matches perfectly with those of our collections of A. sinodeliciosus . The collection 1331 was identified as A. balchaschiensis without any morphological information by Hildén et al. (2013) in a publication focusing on the cultivation of Agaricus species. Our new species also could have been misidentified as A. gennadii (Chatin & Boud.) P.D. Orton (section Chitonioides ) in China because both share similar characters of pileus, stipe, spores and cheilocystidia. However the context discoloration (only pale pink in stipe cortex) in A. gennadii is much less pronounced than in A. sinodeliciosus ; both species differ phylogenetically in agreement with their placement in sections Chitonioides and Bivelares respectively.

Agaricus bitorquis (Quél.) Sacc. in Syll. Fung. 5 (1887: 998).

Known distribution:—Worldwide.

Material examined:— CHINA, Xinjiang Province, Bortala, Ebinur Lake, 10 May 2012, WZR2012 826, WZR2012 827, WZR2012 828, WZR2012 829, all collected by Zhuo-Ren Wang. All in SWFC! and HMAS!.

Notes:—The morphological characters of these four Chinese specimens completely agree with those described from Europe ( Cappelli 1984; Parra 2008) and North America ( Kerrigan 1986).