Volvariella rostricystidiata

Volvariella rostricystidiata Niego, Sysouph., K.D. Hyde & Raspé.

MycoBank MB 835557, Faces of Fungi 08023

Pileus 55–85 mm diam., plano-convex, greyish brown (6E3) with darker pigment at the center becoming lighter towards the margin, dull, dry, non-hygrophanous, matted-fibrillose, appressedsquamulose surface; margin decurved to plane, crenulate; context light yellow, unchanging when cut, with soft consistency. Lamellae free, crowded, moderately thin, soft, subventricose, white when young (10A1) then light pink (10A2); edge finely fimbriate, concolorous with faces; lamellulae present, mostly in one tier. Stipe 65–85 × 3–5 mm, central, terete, dry, brittle, solid, slender, equal to slightly tapered from the base to apex, greyish brown (5D/E3–4) over the entire length, finely and sparsely pubescent above to sparsely flocculose below; context light yellow, unchanging when cut; annulus absent. Volva thick, free, saccate, brittle; outside brownish grey or greyish brown (5–6D/E2–3) to white near the base; inside off-white to orange grey (4–5B3). Spore print pinkish (7A2). Odor indistinct. Taste mild. Basidiospores [60,2,2] (5)5.5–6–6.5(7) × (3.5)4–4.5–5(5.5) μm (Q = 1.2–1.7, Q* = 1.4), ellipsoid to broadly ellipsoid, obovoid, thick-walled, hyaline in 5% KOH. Basidia [30,2,2] (17.5)21–24.5–27(29) × (7)7.5–8.3–9.5(10) μm (Q = 2.4–3.9, Q* = 3.0), tetrasporic, clavate, hyaline in 5% KOH. Cheilocystidia [30,2,2] (51)53–61–68(80) × (14) 18–28–38 (39) μm (Q = 1.5–4.0, Q* = 2.2), numerous, grouped together, pedunculate, mostly obovoid, a few ovoid, ellipsoid or broadly ellipsoid, consistently with rostrate apex (8–22 × 3–6 μm), smooth, thin-walled, hyaline in 5% KOH. Pleurocystidia [30,2,2] (41)47–66–79(117) × (10)13–19–24(25) μm (Q = 3.2–3.8, Q* = 3.6), scattered, pedunculate, slender, mostly fusiform, sometimes broadly cylindrical, narrowly clavate, or oblong, with blunt, rounded apex, smooth, thin-walled, hyaline in 5% KOH. Hymenophoral trama inverse, made of thin-walled, hyaline hyphae. Pileipellis a trichoderm; terminal elements [30,2,2] 58–266 × 16–33 μm, cylindrical; with intracellular light brown (6D8) pigment in 5% KOH. Stipitipellis a cutis; terminal elements long and slender, longer and narrower than in the pileipellis, mostly cylindrical [30,2,2] 74–392 × 13–24 μm, with intracellular light brown (6D8) pigment in 5% KOH. Clamp connections not seen. (Fig. 1–2)

Habitat and distribution: Solitary, on the soil on regularly mown lawn, Chiang Rai Province, Thailand. Additional

Specimen examined: THAILAND. Chiang Rai Province: Mae Fah Luang University, 20.0476°N, 99.8957°E, lawn, 27 September 2018, P. Sysouphanthong, MFLU 19-1531 (GenBank MT074695- ITS, MT078696-nrLSU).

Notes: Volvariella rostricystidiata has a smooth to slightly pubescent solid stipe whereas V. pulla has an entirely pubescent stipe (Malysheva et al. 2019 and this study). Moreover, the cheilocystidia of V. rostricystidiata are mostly clavate to broadly clavate and consistently show a rostrate apex, whereas those of V. pulla are extremely variable in size and shape, ventricose-lageniform, broadly fusiform, spatula-shaped, a small proportion are utriform, sometimes with subglobose or bifurcated apex as described by Malysheva et. al. (2019). In the phylogenetic tree analyses (Fig.1) V. pulla belonged in a different clade than V. rostricystidiata. The cheilocystidia of V. rostricystidiata are somewhat similar to those of V. caesiotincta P.D. Orton (1974: 319), except that the latter has more variable cheilocystidia, which are clavate, fusoid, less frequently subvesiculose or utriform, mostly with a rostrum that is often abruptly connected with a basal part and often irregular, branched to occasionally subcoralloid (Antonín 2012). In our phylogeny, V. rostricystidiata was closely related to V. nivea. However, it is morphologically quite different since the latter has white basidiomes (Li et al. 2009). There are other species morphologically similar to Volvariella rostricystidiata, all having a greyish to greyish brown pileus but all differing from V. rostricystidiata in other features. The American Volvariella bakeri (Murrill 1911:281) Shaffer (1957: 557) is characterized by a dark fuliginous pileus, becoming lighter with age, up to 100 mm in diameter, and larger basidiospores 6.9–9.3 × 4.6–6.9 μm (Shaffer 1957, Wartchow 2009). Volvariella morozovae E.F. Malysheva & A.V. Alexandrova (2017: 343) from Vietnam has smaller (20–45 mm diam.), more delicate basidiomes, a hairy pileus and volva, and mostly ellipsoid or lacrymoid basidiospores (Crous et al. 2017). Volvariella murinella (Quélet 1883: 391) M.M. Moser (1953: 110) known from Europe produces small basidiomes (10–55 mm) that are whitish when young (Boekhout 1986). Volvariella taylorii (Berk. & Broome 1854: 398) Singer (1951: 401) has smaller (20–50 mm diam.), shiny and often subviscid basidiomes (Boekhout 1986, Wartchow 2009, Le & Chu 2018). (from Niego et al.2021)

Fig 1. Phylogenetic tree generated from ML analysis of combined ITS and nrLSU data set for Volvariella with outgroup of three species of Cantharocybe and three species of Cuphophyllus. Boostrap support values (≥70%) and posterior probabilities (≥0.9) (BS/PP) are given above the branches. All terminals are with species name and voucher ID, with the newly generated sequences from this study in bold.