Stropharia lignicola E.J. Tian, 2021

Tian, Enjing, Gao, Chonghua, Xie, Xiaomei & Zheng, Yuan, 2021, Stropharia lignicola (Strophariaceae, Agaricales), a new species with acanthocytes in the hymenium from China, Phytotaxa 505 (3), pp. 286-296 : 293-294

Stropharia lignicola E.J. Tian sp. nov. ( Figs. 2 , 3 )

MycoBank:—MB838568

Diagnosis:— Stropharia lignicola is distinguished from other known species of the genus Stropharia by the greyish yellow pileus, white stipe with recurved yellowish squamules, the presence of the acanthocytes in both the hymenium and the stipe basal mycelium. Etymology:— lignicola , refers to its preference for growing on decaying fallen wood or stumps. Type:— CHINA. Hunan Province: Xiaoxi National Nature Reserve, Yongshun County, 510 m elev., 29 August 2014, P. Zhang 37429,

Holotype ( HMJAU!). GenBank: ITS= MW 492530 ; 28 S = MW 492633 .

Description:— Pileus 30–75 mm diam, hemispheric to convex, expanding to broadly convex with an incurved margin, obtusely umbonate; color greyish yellow (4B4–4B6), paler towards the margin; surface viscid, covered with pale tawny appressed spot-like squamules, or with slightly recurved to squarrose white scales at times; the margin at first appendiculate with pale yellow veil remnants. Context fleshy, whitish, odor and taste mild. Lamellae adnate, flesh (6B3) to camel (6D4), close, margins even, concolorous with faces. Stipe 40–50 mm long, 8–18 mm thick, central, dry, equal or slightly enlarged at base, color white, surface covered with recurved yellowish squamules towards base, hollow, white basal mycelium and well-developed rhizomorphs. Partial veil forming a yellowish membranous, sometimes evanescent annulus.

Basidiospores (4.8)5–6 × 3.2–4.2(–5) μm, Q = 1.25–1.72, Q m = 1.43±0.12, elliptical to subovate in face-view, inequilateral in side-view, wall smooth and thickened, germ pore minute, pale rusty to pale dull tawny in KOH and Melzer’s reagent, sometimes paler in the latter. Basidia 18–27 × 6.5–8.9 μm, 4-spored, clavate, hyaline in KOH. Pleurocystidia as chrysocystidia, abundant, 17–34 × 5.5–11 μm, clavate, some tapering slightly near apex, thinwalled, smooth, hyaline in KOH, with an amorphous highly refractive yellowish brown content. Cheilocystidia thinwalled, smooth, 17–47 × 9.5–23 μm, clavate, with homogenous content. Caulocystidia absent. Gill trama of parallel to subparallel hyphae 2.5–9.8 μm diam, smooth, thin-walled, hyaline to yellowish in KOH. Pileipellis composed of yellowish to yellowish brown hyphae, 2–10 μm wide, with slight external incrustation. Context hyphae thin-walled, smooth, hyaline in KOH. Acanthocytes present in both the hymenium and the basal mycelium of stipe, thick-walled, with 6–13 pointed branches. Clamp connections present in all tissues.

Habitat:—Gregarious to caespitose on decaying wood or stumps of Tilia sp. in a broad-leaved forest, in late summer and autumn.

Material examined:— CHINA. Hunan Province: Xiaoxi National Nature Reserve , Yongshun County, 510 m elev., 29 August 2014, Ping Zhang 37429, (holotype, HMJAU!); same location, 5 September 2015, G . Cao 37510, ( HMJAU!) . USA. Tennessee: South Knoxville, Residential area , 15 August 2017, G . Burghardt TENN-F-071760, ( TENN!) ( Stropharia hardii )

Comments:—This species is characterized mainly by the greyish yellow pileus, white stipe with recurved yellowish squamules, lack of caulocystidia, presence of acanthocytes in both hymenium and mycelium at base of stipe, and growth on hardwood stumps.

The recurved yellowish squamules of the stipe and the habitat on decaying hardwood would suggest its placement in Pholiota . However, Stropharia lignicola is excluded morphologically from Pholiota based on the presence of acanthocytes, and molecularly, by the phylogenetic analyses in this study ( Fig. 1 ).

Stropharia lignicola is closely related to S. acanthocystis , S. apiahyna and S. coelhoi due to all species having cystidium-like acanthocytes in the hymenium ( Cortez & Silveira 2007, 2008; Seger et al. 2016). However, they are morphologically distinct. S. acanthocystis has a reddish brown, red to yellowish red pileus, pale yellow longitudinally striate stipe, and slightly larger basidiospores (6–7 × 4–5 μm) ( Cortez & Silveira 2007, 2008). S. apiahyna has a smaller pileus with a subtomentose to glabrous surface, a slim stipe with fibrils on the surface, and larger basidiospores (6–8 × 3.5–5 μm) ( Cortez & Silveira 2008). S. coelhoi has a dark brown pileus with a smooth surface and larger spores (10.5–14 × 6.5–8 μm) with a broader germ pore ( Seger et al. 2016).

In the phylogram ( Fig 1 ), Stropharia lignicola is sister to S. hardii G.F. Atk. (1906: 194) and S. acanthostipitata Angelini & Vizzini (2017: 158) . When studying the specimen of S. hardii from Tennessee, USA (TENN-F-071760), we found that S. hardii is different from S. lignicola in the absence of hymenial acanthocytes, the spores without an obvious germ pore and the habitat, as it grows on soil not wood. S. acanthostipitata also can be easily distinguished from S. lignicola by the absence of hymenial acanthocytes ( Vizzini et al. 2017).

Figures

FIGURE 1. ML phylogram of Stropharia and allied genera inferred from dataset (ITS+28S). Bayesian PPs>0.90 and bootstrap values>70% are shown.

FIGURE 2. Basidiomes of Stropharia lignicola (HMJAU 37429). Photo by P. Zhang. Bars = 1 cm.

FIGURE 3. Microcharacters of Stropharia lignicola (HMJAU 37429).A. Cheilocystidia; B. Basidiospores; C. Pleurocystidia; D. Basidia; E. Acanthocytes; F. Pileipellis. Bars = 10 μm. Drawings by E.J. Tian.