Volvariella caesiotincta P.D. Orton

Caballero, Fernando, Justo, Alfredo, Parra, Luis A., Angelini, Claudio, Consiglio, Giovanni, Dovana, Francesco, Ferisin, Giuliano, Kaygusuz, Oğuzhan, Knudsen, Henning, Llimona, Xavier, Muñoz, Guillermo, Daniëls, Pablo P., Pérez-De-Gregorio, Miquel À., Ševčíková, Hana, Valverde, Andrés & Vizzini, Alfredo, 2025, Taxonomic and phylogenetic overview of the genus Volvariella (Volvariellaceae), with a focus on European species, Phytotaxa 680 (1), pp. 1-85 : 20-25

2. Volvariella caesiotincta P.D. Orton , Bulletin Mensuel de la Société Linnéenne de Lyon 43 (Num. Spéc.): 319. 1974. ( Figs. 9–10 )

= Volvariella lanata E.F. Malysheva in Malysheva & Malysheva, Phytotaxa 636(1): 79 (2024)

Typification status:— Holotype: United Kingdom, England, Norfolk, Surlingham, Tucks Plantation , on elm ( Ulmus sp. ), 27 August 1969,

P.D. Orton 3805!, barcode E00429678 (E).

Description:— Pileus 25–70(–120) mm diam., ovoid when young, expanding to convex or conico-convex, then applanate, sometimes subumbonate; surface silky-fibrillose, typically with the fibrils grouped into small radially arranged squamules, sometimes radially cracked from the disc to the margin, grey, grey-brown, bluish grey, olive or greenish grey, sometimes with a metallic tint, dry, slightly hygrophanous; margin not striate, slightly irregular and exceeding the lamellae. Lamellae crowded to moderately crowded, free, broadly ventricose, white when young, becoming salmon pink or pinkish brown with age, with entire to slightly irregular edge, paler than the sides. Stipe 30– 110 × 4–14 mm, up to 20 mm wide at the base, cylindrical to subclavate, straight or curved; surface white, sometimes with yellow to orange tinges on touch, smooth to pubescent. Volva membranaceous, often delicate; outer surface off-white, grey, grey-brown; inner surface of similar colour variation, sometimes with orange tinges; with 2–3 lobes, or with just one longitudinal indentation; rhizomorphs sometimes present, especially in apparently terrestrial specimens that are connected to wood. Context white to pale beige with indistinct to strongly fungoid smell.

Basidiospores (n=2500, c=38) (5.6–)5.9–8.4(–10.4) × 4.0–5.9 μm, avl × avw = 6.9 × 4.9 μm, Q = 1.07–2.27, avQ = 1.48, subglobose to cylindrical, thick-walled, with barely distinct hilar appendage. Basidia 20–33 × 8–10 μm, tetrasterigmate, clavate, subclavate or subcylindrical. Lamella edge sterile or heterogeneous. Cheilocystidia common, (28–)43–116(–135) × (10–)14–38(–46) μm, fusiform, lageniform or utriform, some with 1–3 finger-like, flexuous or coralloid projections, up to half of the total length of the cystidia, sometimes with crystals at apex, hyaline, thin-walled. Pleurocystidia scarce, 39–74 × 15–31 µm, scattered, clavate, fusiform or utriform, without apical projections. Pileipellis a cutis or an intermediate cutis-trichoderm, with terminal elements (28–)60–360 (–500) × 8.5–37(–57) μm, commonly with diffuse intracellular pigment, more rarely granular or vacuolar, olive green, brown or dark brown, some colorless. Stipitipellis a cutis or a cutis-trichoderm in the upper part of the stipe, with cylindrical hyphae, 2–18 μm wide. Caulocystidia 12–40 × 4–17 µm, fusiform; in the upper part of the stipe (not present in all collections). Hyphae of the rhizomorphs, densely packed, composed of three different types (intermixed): hyphae up to 1.5–2.6 µm wide, barely septate, with diffuse, intracellular yellow-green pigment, with clamp connections; multiseptate hyphae up to 3.3–4.2 µm wide, thick-walled, with diffuse intracellular olive green or brown pigment, with clamp connections; hyphae up to 7.7–11.9 µm wide, with short projections (acanthohyphae) with oleaginous content. Sometimes with terminal subclavate or lageniform elements similar to cystidia, with clamp connections at base, with granular intracellular olive green or dark brown pigment. Volva composed of interwoven, cylindrical hyphae, 3–26 μm wide, with few septa; on the lower and external surfaces often gelatinized. Clamp connections absent in all parts examined, except for some hyphae in the rhizomorphs.

Habit, habitat, and phenology:—Solitary or gregarious in groups of up to 3–4 basidiomes. Commonly growing on living trees, dead stumps and branches of angiosperms, mostly Populus , Ulmus and Fagus , very rarely on conifer wood ( Pinus ). It has also been collected without direct connection to wood, growing on the ground, often among leaves, under different tree species ( Acacia , Acer , Eucalyptus , Fraxinus , Picea , Platanus , Quercus ). Mostly fruiting June–November, but collected all year round, even during winter in temperate and Mediterranean Europe.

Distribution:—Widespread in temperate and Mediterranean Europe, also known from Turkey. Widely reported, but precise distribution is difficult to know due to the likelihood of confusion with other species.

Additional collections examined:— CZECH REPUBLIC. Moravia: Babice nad Svitavou, Čihadlo Nature Reserve, beech forest, fallen decaying Fagus trunk, no date 2017, P. Včelička, BRNM844472; ibid., decaying trunk of Fagus , 27 September 2017, H. Ševčíková, BRNM805995; ibid., on soil under Fagus sylvatica , 16 September 2018, H. Ševčíková, BRNM844466; Brno, Hádecká planinka National Nature Reserve, elev. 400–424 m, on soil, under Quercus petraea and Acer campestre , 11 August 2010, V. Antonín, BRNM733259; Brno, Hády, elev. 385 m, wet place in mixed forest above the southern tip of the forest quarry, large decaying Tilia stump, 6 September 2013, H. Ševčíková, BRNM792958; Brno, Bystrc, Jelení žlíbek Nature Reserve beech forest, fallen decaying Fagus trunk, 1 July 2016, V. Antonín, BRNM792941; ibid., decaying trunk of Fagus , 1 July 2016, H. Ševčíková, BRNM792940; Březník, Divoká Oslava National Nature Reserve, mixed forest under the Lamberk castle by the river Oslava, fallen deciduous trunk, 1 October 2017, H. Ševčíková, BRNM793296; Křtiny, NR Bayerova, decaying deciduous trunk, 11 October 2017, H. Ševčíková, P.Ševčík, BRNM793327; Kuřim, Bělč forest, deciduous stump, 27 September 2018, V.Antonín, H.Ševčíková, BRNM844465; Lažánky u Veverské Bítýšky, Slunná Nature Reserve beech forest, fallen decaying Fagus trunk, no date, H. Ševčíková, BRNM788397; Sidonie, NPR Sidonie, decaying trunk of Fagus , 21 August 2020, S. Flekrová, J. Hrabáková H. Ševčíková, BRNM844461; Valtice, NPR Rendez-vous, near fallen Quercus trunk, 10 June 2017, P. Včelička, BRNM844471; ibid., on decaying Quercus trunk, 2 June 2023, H. Ševčíková, K. Ševčíková, BRNM844470. FRANCE. Vienne: Vouille, on the slope of a forest path, bordering a forest of mixed deciduous and coniferous trees, on black and damp soil covered with woody and leafy debris, 26 October 2022, F.X. Boutard s.n. ITALY. Latina: Priverno, in a mixed forest of broadleaved trees, 28 October 2009, G. Consiglio, AMB19319; Udine: Cividale (Bosco Romagno), on soil under broad-leaved trees, 1 October 2022, G. Ferisin, FG0110202213. SLOVAKIA. Chvojnická pahorkatina, Radošovce, Čaňov, deciduous forest, on decaying deciduous tree, 11 June 2016, BRNM844469. SLOVENIA. Tolmin, under Fagus sylvatica and Fraxinus sp. , 12 July 2007, J. Kavcic, TOAV143. SPAIN. Barcelona: Olzinelles, in soil, in a mixed forest of Alnus sp. , Populus sp. and Platanus hispanica , 2 December 2001, M. Tabarés, A. Rocabruna, BCN3921; Parc de la Serralada Litoral, Martorelles, elev. 280–300 m, in a broadleaved mixed forest in sandy acid soil, with Populus alba , P. nigra and Corylus avellana , on dead P. nigra tree stump, 6 October 2015, F. Caballero, SFC 151206- 01; ibid., 8 October 2015, F. Caballero, SFC 151208-01; ibid., 30 April 2016, F. Caballero, SFC 160430-01; ibid., 7 May 2016, F. Caballero, SFC 160507-01; ibid., 21 May 2016, F. Caballero, SFC 160521-01; ibid., 2 October 2016, F. Caballero, SFC 161002-01; ibid., 9 October 2016, F. Caballero, SFC 161009-01; ibid., 12 October 2016, F. Caballero, SFC 161012; ibid., 23 October 2016, F. Caballero, SFC 161023-01; ibid., 29 October 2016, F. Caballero, SFC 161029- 01; ibid., 6 November 2016, F. Caballero, SFC 161106-01; ibid., in soil under Quercus ilex , 12 November 2016, F. Caballero, SFC 161112-01; ibid., in humus under Platanus hispanica , 20 November 2016, F. Caballero, SFC 161120- 01; ibid., 3 October 2017, F. Caballero, SFC 171003-01; ibid., 1 November 2017, F. Caballero, SFC 171101-01; ibid., on living Populus nigra tree, 5 November 2017, F. Caballero, SFC 171105-01; ibid., 12 November 2017, F. Caballero, SFC 171112-01; ibid., 18 November 2017, F. Caballero, SFC 171118-01; ibid., 12 May 2018, F. Caballero, SFC 180512- 01; ibid., 27 May 2018, F. Caballero, SFC 180527-01; ibid., on a dead Populus nigra tree, 1 November 2018, F. Caballero, SFC 181101; ibid., 4 November 2018, F. Caballero, SFC 181104; ibid., 11 November 2018, F. Caballero, SFC 181111; ibid., 24 November 2018, F. Caballero, SFC 181124; ibid., 15 June 2019, F. Caballero, SFC 190615; ibid., 29 September 2019, F. Caballero, SFC 190929; ibid., 1 November 2019, F. Caballero, SFC 191101; ibid., 17 November 2019, F. Caballero, SFC 191117; ibid., 6 October 2021, F. Caballero, SFC 211006; ibid., 23 October 2021, F. Caballero, SFC 211023; ibid., 31 October 2021, F. Caballero, SFC 211031; ibid., 14 November 2021, F. Caballero, SFC 211114; Gipuzkoa: Aia, Laurgain Natural Park, on soil under Picea abies , 26 August 2000, J.L.A. Albizu, ARANFungi A3033125; Astigarraga on Pinus radiata , 18 November 2002, J.M. Lekuona, ARAN-Fungi A3004061; Girona: Serinyà, Pla de l’Estany, on humus of Quercus ilex , 1 June 2013, J. Carbó, JC20130601-2; La Rioja: Tudelilla, on soil close to a Populus nigra tree stump, 1 October 2006, G. Muñoz, GM764; ibid., in soil between Populus nigra and Quercus ilex , 1 June 2008, G. Muñoz, GM1265; ibid., 8 June 2008, G. Muñoz, GM1283; Navarra: Etxarri, Larraun Valley (Navarra), on Fagus sylvatica , 12-10-2000, P.M. Pasaban, ARAN-Fungi A5037215; Orokieta, Navarra, on soil under Picea abies , 10 October 2009, J.L.A. Albizu, ARAN-Fungi A5041237; Ulzama Valley, (Navarra), in soil under a Fagus sylvatica tree, 20 June 2016, L.M. García-Bona, LMGB 4961. Pontevedra: O Grove, in a hollow trunk, in a mixed forest with Acacia sp. , Quercus sp. and Eucalyptus sp. , 10 November 2018, M.A. Delgado, J5751; Valladolid: Tordesillas, in soil between Populus nigra and Quercus ilex , 21 October 2013, J.Z. Ramos, AVM 3114. TURKEY. Bolu: Seven Lakes National Park, near Deringöl, elev. 165 m, on decaying trunks of Fagus orientalis , 20 October 2015, O. Kaygusuz, OKA-TR362; ibid., elev. 163 m, on decaying trunks of F orientalis , 21 October 2015, O. Kaygusuz, OKA-TR363; ibid., elev. 172 m, on wood of F. orientalis , 23 October 2016, O. Kaygusuz, OKA-TR372. Bursa: Uludag National Park, in Karabelen, elev. 685 m, on Fagus orientalis , 24 October 2016, O. Kaygusuz, OKA-TR459; ibid., elev. 688 m, on decaying trunks of F. orientalis , 19 October 2017, O. Kaygusuz, OKA-TR473. Karabük: Yenice Forests, elev. 235 m, on decayed wood of F. orientalis , 21 October 2014, O. Kaygusuz, OKA-TR278; ibid., elev. 230 m, on wood and fallen branch of F. orientalis , 24 October 2014, O. Kaygusuz, OKA-TR321. UNITED KINGDOM: England: Middlesex, on wood, 14 August 2015, A.S. Overall, K(M)199931; Norfolk, Surlingham, Tucks Plantation, on elm ( Ulmus sp. ), 23 August 1969, P.D. Orton, Orton3803, (E); West Kent, Lullingstone, in soil under Fagus sylvatica , 1 July 2016, A. Henrici, K(M)206747 (as Volvariella pusilla ).

Observations:—The above description is based exclusively on the collections examined for this study. We have chosen not to include additional data on ecology or chorology from collections in the literature without molecular data, as they might not represent V. caesiotincta as circumscribed here.

Malysheva and Malysheva (2024) recently described V. lanata which also possesses mucronate cheilocystidia with flexuous, finger-like projections. However, its nrITS sequence is nearly identical to the sequence of the type of V. caesiotincta . Malysheva and Malysheva (2024) mentioned the shorter cheilocystidia of V. caesiotincta as a distinguishing character but our studies indicate that such variation falls within the normal range for this species. They also cited the lack of smell in V. lanata as separating it from V. caesiotincta , often described as having a smell reminiscent of Geranium robertianum , but odorless collections of V. caesiotincta also exist. The only character that contributes to a greater morphological variability of V. caesiotincta is the size and shape of the pleurocystidia in V. lanata : up to 90 μm long, utriform or broadly fusiform, and sometimes with a broad subcapitate apex.

Orton (1974) and Antonín (2012) referred to the close affinities of V. caesiotincta with V. volvacea , V. murinella and V. taylorii and dealt with the taxonomic problem of separating these species properly. Characters that have been used to separate V. caesiotincta include habitat, outer colour of the volva, spore shape and size, pileipellis structure, and the presence of branched projections on the cystidia. After the present study we characterize V. caesiotincta by its direct or indirect (via rhizomorphs) lignicolous habit, the greyish brown volva, the occasional presence of blue or green/olive shades on the pileus, the presence of intracellular vacuolar pigment in the pileipellis hyphae and the finger-like to coralloid projections on the cystidia.

Volvariella murinella is macroscopically very similar, but the pileipellis hyphae contain no vacuolar pigment. Volvariella taylorii differs by the overall less robust basidiomes. Both species lack a distinct radially fibrillose to streaky dark pileus, and lack blue or olive green shades. Due to the greyish volva and pileus, V. caesiotincta could also be confused with V. terrea , V. dunensis and V. volvacea . Volvariella terrea has a fibrillose to lanate pileus, a pileipellis with pale brownish, non-vacuolar, intracellular pigment and fruits in association with Agaricus xanthodermus Genev. (1876: 31) . Volvariella dunensis differs mainly by its occurrence in dune habitats. Volvariella volvacea has larger spores, and does not have narrow and acute terminal elements in the pileipellis, nor blue shades on the pileus. None of the above-mentioned species have rhizomorphs, nor cheilocystidia with finger-like or forked apical projections, and do not grow on wood.

Rhizomorphs were present in nine collections of V. caesiotincta made on soil. These rhizomorphs connect to woody substrate underground, and provide us with additional taxonomic characters for Volvariella . Rhizomorphs often have clamped hyphae, which is unusual in Volvariella . One collection (SFC191101) has terminal hyphae similar to subclavate to lageniform cystidia with a clamped base. Given the fact that several studies on Coprinus Pers. , Conocybe Fayod , Geastrum Pers. , Paralepista Raithelh. , Ramaria Fr. ex Bonord. , Rhodophana Kühner and Stropharia (Fr.) Quél. have demonstrated the existence of differentiated structures in the vegetative mycelium with taxonomic significance such as cystidia, skeletized hyphae, acanthohyphae, oxalate crystals, chlamydospores, and cysts ( Christan 2008; Clémençon 2003; Daniëls et al. 2017; Horner et al. 1995; Hutchison et al. 1996; Luo et al. 2006, 2007; Zamora et al. 2013, 2015), more studies of the vegetative structures and mycelium of Volvariella are needed, to know their taxonomic relevance.

Spore measurements of some specimens vary seasonally from autumn to spring, even among collections from the same location. In autumn, spores are irregularly ellipsoid to subcylindrical, (n = 137) 6.3–10.4 × 3.8–5.6 µm, avl × avw = 7.9 × 4.6 µm, Q = 1.29–2.27, avQ= 1.73 (SFC151206). In spring, they are (n=54) 6.1–7.2 × 4.7–5.9 µm, avl × avw = 6.7 × 5.2 µm, Q = 1.17–1.48, avQ = 1.29 (SFC160430).

Collections of V. caesiotincta exhibit wide morphological plasticity, possibly in part because of environmental factors, but molecular data clearly point to the existence of one single species.

Volvariella caesiotincta has been considered a rare species, and it has been included in European red data lists for Austria, Sweden, Slovakia, Denmark, The Netherlands, Norway, Finland and Germany ( Arnolds & Kuyper 1996; Halama 2009; Senn-Irlet et al. 2007; Krisai-Greilhuber 1999). It is not common in Spain but seems to be widespread. In the Czech Republic this species was stated as a particularly protected species in the category “highly endangered species” (Decree of the Ministry of the Interior No. 395/1992 Coll) and the Red List of Macromycetes of the Czech Republic in the category ‘Vulnerable Species’ (Vágner in Holec & Beran 2006). However, due to its abundant occurrence, especially in Moravia, it was not included in the updated Red List of Fungi (Macromycetes) of the Czech Republic ( Zíbarová et al. 2024). The data presented here suggest that V. caesiotincta is widespread and relatively common in Europe, extending at least into Turkey.

Figures

FIGURE 9. Volvariella caesiotincta. A–N. Basidiomes. A. (SFC161002); B (SFC171003); C (SFC151208); D (SFC160521); E (SFC171112); F (SFC171105); G (SFC171118); H (SFC180527); I (SFC171101); J (SFC191101); K (GM764); L (SFC211023); M (GM1283); N (AVM 3114). Photos by F. Caballero (A–J, L), G. Muñoz (K, M), J.Z. Ramos (N).

FIGURE 10. Volvariella caesiotincta. A–N. Microscopic characters. A–D. Cheilocystidia A. (P.D. ORTON 3805, holotype); B. (A5037215); C. (SFC161112-01); D. (TOAV143); E. Cheilocystidia; F. Pleurocystidium (SFC171105); G. Spores (P.D. ORTON 3805, holotype); H. Pileipellis (SFC171112-01); I. Volva hyphae (SFC161120-01); J–N. Rhizomorphs, J–K (SFC200927), L–N (SFC190901). Bar: (A–H, K–N) = 10 µm; (I–J) = 100 µm. Photos by F. Caballero (A–N).