Volvariella izmirensis Kaygusuz & Knudsen, 2025

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 : 63

21. Volvariella izmirensis Kaygusuz & Knudsen sp. nov. ( Fig. 29 ).

MycoBank: MB 856538

Typification:— Holotype: TURKEY. İzmir, KemalpaŞa, Bayındır , Bagyurdu , on alluvial sandy soils, under Populus alba , 10 May 2021, O. Kaygusuz, OKA-TR3535, GUL1027 !.

Etymology:—From the Latin “ izmirensis ” meaning from İzmir ( Turkey), the province where the holotype was found.

Diagnosis:— Volvariella izmirensis is mainly characterized by its small to medium basidiomes, white to pale beige pileus with cinereous centre, golden brown to ochre brown saccate volva, mainly narrow fusiform to fusiform pleurocystidia with an elongated neck and acute apex, lageniform to fusiform cheilocystidia with moniliform to flexuous excrescence, elongated clavate or obovoid caulocystidia, and thermophilic habitats with alluvial soils.

Description:— Pileus 20–60 mm diam., hemispherical to convex, then plano-convex to applanate, with slightly depressed centre when mature, non-striate margin, surface dry, not hygrophanous, white to pale beige, finally at centre very pale brown to cinereous, radially silky fibrillose to fibrillose-squamulose with some erect short white hairs, sometimes cracked in older basidiomes. Lamellae crowded to moderately crowded, free, thin, ventricose, first white to very pale pink, then pinkish brown, finally almost entirely salmon pink, with concolorous even edge. Stipe 20–60 × 2.0–4.0 mm, cylindrical, slightly broadened downward, surface white, pubescent all over. Volva 2–5 mm high, thick, free, trilobate, saccate, fragile, golden brown to ochre brown; rhizomorphs not observed. Context white to cream, with indistinct smell.

Basidiospores (n=185, c=4) (6.6–)6.8–9.5(–10.8) × (4.0–)4.2–5.4(–5.9) µm, avl × avw = 8.0 × 4.8 µm, Q = (1.42–)1.54–1.91(–2.0), avQ = 1.75, ellipsoid to oblong, slightly thick-walled, smooth, with a large central (oil) drop, hyaline. Basidia 20–30 × 7.5–8.5 µm, narrowly to broadly clavate often inflated in the middle, tetrasterigmate to bisterigmate, occasionally monosterigmate, hyaline, thin-walled. Lamella edge sterile. Cheilocystidia common, 25–45 × 9–15 µm, abundant, mainly lageniform to fusiform with moniliform to flexuose excrescence, sometimes with finger-like appendage, hyaline, thin-walled. Pleurocystidia common, 40–65(–70) × 10–16 µm, predominantly narrowly fusiform to fusiform, usually with an elongated neck and acute apex, hyaline, thin-walled. Pileipellis a cutis, with cylindrical terminal elements 50–170(–220) × 10–20 µm, non-gelatinous, smooth, hyaline or with pale yellowish brown intracellular pigment, thin-walled. Stipitipellis a cutis, compose of elongated cylindrical elements, 4–15 μm wide. Caulocystidia common, 50–110(–130) × 15–33 µm, mostly narrowly clavate or obovoid, in bundles, hyaline, thin-walled; present in the upper part of the stipe. Volva composed of interwoven, cylindrical hyphae, 4–35 μm wide, with common septa; individual segments sometimes with pale brown, diffuse, intracellular pigment. Clamp connections absent in all tissues examined.

Habit, habitat, and phenology:—Gregarious or in small scattered groups, on alluvial sandy soils, at an elevation of about 80 m, in a Mediterranean climate, in a forest of old Populus alba trees. May.

Distribution:—So far only known from Turkey.

Additional collections examined:— TURKEY. İzmir Province, KemalpaŞa, Bayındır district, in Bagyurdu, on alluvial sandy soils, under Populus alba , 23 May 2021, leg. O. Kaygusuz, OKA-TR3536; ibid., on alluvial soil, under P. alba , 9 May 2022, leg. O. Kaygusuz, OKA-TR3537 ; ibid., on alluvial soil, under P. alba , 17 May 2022, leg. O. Kaygusuz, OKA-TR3538 ; ibid., on alluvial soil, under P. alba , 19 May 2023, leg. O. Kaygusuz, OKA-TR3539 .

Observations:—The closest relative of V. izmirensis in the molecular phylogenetic analysis is the European V. cordispora ( Fig. 4 ), which is clearly distinguished from V. izmirensis by its white pileus with a pale brown colour at the centre, frequent heart-shaped, smaller basidiospores (6.0 × 4.6 µm on average), different pleurocystidia, no caulocystidia, and ruderal habitat. Further species related to V. izmirensis are V. lepiotospora Singer (1955: 774) and V. ptilotricha . Volvariella lepiotospora from North America differs by a darker pileus colour, smaller basidiospores (4.7–6.3 × 2.8–3.8 µm), and smaller clavate cheilocystidia (up to 26 µm long) ( Singer 1955, Shaffer 1957). Volvariella ptilotricha from tropical Vietnam differs by its strongly pubescent basidiomes with greyish brown pileus, smaller basidiospores (5.5 × 4.0 µm on average), and clavate pleurocystidia ( Malysheva et al. 2019).

The morphologically similar European species are V. caesiotincta , V. hypopithys , V. neoparvula , V. pusilla , V. reidii , V. taylorii and V. turcica O. Kaygusuz & H. Knudsen ( Kaygusuz et al. 2020: 580) , which are all phylogenetically distant. For a morphological comparison between these species see Tables 1 and 2.

Figures

FIGURE 4. Best tree from the Maximum Likelihood analysis of the ITS dataset of Volvariella: detailed view of the lineage including V. hypopithys and related taxa. BS ≥ 70 % and PP ≥ 0.90 are shown on or below the branches. Newly described taxa are highlighted in red.

FIGURE 29. Volvariella izmirensis. A–D. Basidiomes. A. (GUL1027, holotype); C. (OKA-TR3536); C. (OKA-TR3537); D. (OKA- TR3538). E–I. Microscopic characters (GUL1027, holotype). E. Cheilocystidia; F. Pleurocystidia; G. Spores; H. Pileipellis; I. Stipitipellis. Bar: (E–I) = 10 µm. Photos by O. Kaygusuz (A–D). Drawings by O. Kaygusuz (E–I).