Phylogeny of the genus Volvariella with the description of one new species and two new records from Oman

Abstract

In the present study, a newly found species of Volvariella from Oman is described and named V. darbatica. Evidence for this decision is based on morphology and multigene phylogeny. Volvariella darbatica is characterized by small-sized basidiomata, pale pinkish to pale brownish pileus, and ellipsoid to ovoid basidiospores measuring 5.0–6.0 × 4.0–4.5 µm. Colour photographs of basidiomata and illustrations of anatomical characters are provided, along with the phylogenetic trees of the genus Volvariella and the suborder Pluteineae (where family Volvariellaceae is nested). Morphological similarities with closely related species are discussed. Furthermore, we also report the presence of Volvariella cubensis and V. sathei in Oman, extending the distribution of these species. Volvariella sathei was previously known only from its type locality in India.

Citation: Hussain S, Al-Kharousi M, Al-Maqbali D, Al-Owaisi AA, Velazhahan R, Al-Sadi AM, Al-Yahya’ei MN (2025). Phylogeny of the genus Volvariella with the description of one new species and two new records from Oman. 16: 29–39. doi: 10.3114/fuse.2025.16.2

INTRODUCTION

The genus Volvariella was introduced by Spegazzini (1899). The name refers to the presence of a volva (wrapper, covering or integument) at the base of the stipe of these mushrooms. Volvariella is characterized by a pileostipitate basidiome, small to medium-sized (rarely large-sized), with a fibrillose to strigose pileus surface, free lamellae, brownish-rose spore print, smooth stipe with no annulus, and the presence of a volva at the base of the stipe. Microscopically, species of Volvariella have smooth basidiospores smaller than < 11 µm in length, which are also in-amyloid, non-dextrinoid, and lack a germ-pore, 4-spored basidia, presence of both cheilo- and pleurocystidia, inversely arranged hyphae in lamellae, absence of clamp connections, and a non-gelatinous pileipellis (Orton 1986, Boekhout 1990, Kirk et al. 2008, Justo et al. 2011, Vizzini et al. 2024).

There are nearly 125 described species in the genus, with Volvariella argentina being the type species (Malysheva et al. 2019, Chattopadhyay et al. 2022, Kumla et al. 2022, Haqnawaz et al. 2023, Caballero et al. 2025, Jabeen et al. 2025). However, databases like Index Fungorum (https://www.indexfungorum.org/; accessed on 7 May 2024) and MycoBank (https://www.mycobank.org/; accessed on 7 February 2025), report 166 and 168 names associated with Volvariella, respectively. Some of the names mentioned in these databases are illegitimate or invalid, and include names widely accepted as heterotypic synonyms or infraspecific names. Ecologically, species of the genus occur as saprotrophs on wood, woody debris, and on soil, spread over the eastern and western hemispheres in tropical, subtropical, and temperate climates, with no reports from artic or alpine regions (Shaffer 1957, Boekhout 1990).

Species of Volvariella were classified into two sections, namely sect. Macrosporae and sect. Volvariella by Contu (1998). This classification was based on basidiospore size, with species in Macrosporae having spores larger than 11 µm in length, and those in sect. Volvariella having spores generally smaller than 11 µm. Later, species in sect. Macrosporae were moved to the independent genus Volvopluteus (Justo et al. 2011). Volvopluteus differs from Volvariella by its smooth cap surface, basidiospores longer than 11 µm in length, and the presence of a gelatinous matrix in the pileipellis. Phylogenetically, Volvopluteus is more closely related to Pluteus in Pluteaceae (Vizzini et al. 2024). The systematic position of Volvariella was controversial for a long time, being placed in Amanitaceae (Lee et al. 1959), Agariaceae (Lee 1973), and finally transferred to Pluteaceae (Singer 1986). Later, Volvariella was thought to have a closer relationship with Cantharocybe and Cuphophyllus in the family Hygrophoraceae (Justo et al. 2011). As a result of the uncertainty, the genus was treated as incertae sedis by other authors (Niego et al. 2021, Kumla et al. 2022). In a recent study of Agaricales based on a 6-gene phylogeny, species of Volvariella formed a separate lineage inside the suborder Pluteineae, and a new family Volvariellaceae was coined for it (Vizzini et al. 2024).

The present study is a continuation of mushroom exploration research in Oman. Oman is situated on the southeast coast of the Arabian Peninsula’s. The samples were collected in Dhofar region of Oman, which experiences a yearly monsoon rain season from June to September, about 100–400 mm in these months (Bookhagen et al. 2005. Kwarteng et al. 2009). Research on mushroom diversity in the Sultanate of Oman has started only very recently, and only nine species have been reported from the entire country so far (Al-Kharousi et al. 2022a, b, Hussain et al. 2022a, b, 2024a–c). In the present work, several collections of Volvariella from Oman are studied. Upon morphological and phylogenetic analyses, these collections contain one new species and two new records of Volvariella from Oman, which are subsequently treated below.

MATERIALS AND METHODS

Sampling and morphological characterization

Basidiocarps were found in August and September, during the rainy season of the years 2022 and 2023. The specimens were found on logs, tree trunks, and soil in Wadi Darbat and Wadi Jarzeez, located in Dhofar region, southern Oman, and photographed in their natural habitat. Macromorphological characters such as size, shape, and colour of basidiocarps were recorded based on fresh materials. Basidiocarps were then dried in a fruit dehydrator set to 45 °C, sealed in zipper bags, and subjected to −80 °C for 2 wk to prepare them for long term preservation.

For microscopic studies, a thin section of the lamellae, pileus covering, and volva were mounted on glass slides, stained with 5 % aqueous KOH, and further stained with 1 % aqueous Congo red for better contrast. Different microscopic structures such as basidiospores, basidia, cystidia, pileipellis, volval structure, etc. were examined under a compound microscope (ECLIPSE Ni-U, Nikon Co., Ltd., Japan). For basidiospores, at least 50 spores were measured at 1000×, and measurements are presented as: (a–)b–c(–d) × (e–)f–g(–h), [, Qm, n] where b–c and f–g include the spore length and width respectively between the 5th and the 95th percentile, (a) and (d) the extreme values of spore lengths recorded, (e) and (h) the extreme values of spores width recorded, the mean of length and width of basidiospores with ± SD (standard deviation) respectively, Qm the mean of Q coefficient (length/width ratio), n is the total number of basidiospores measured (Nawaz et al. 2024). All the samples are preserved at the Oman Animal and Plant Genetic Resources Center (Mawarid), Muscat, Oman.

DNA extraction, amplification, and sequencing

The X-AMP DNA extraction kit (Dubuque, Iowa, USA) was employed following the manufacturer’s instructions to isolate genomic DNA from dried materials. Three DNA regions were amplified, including the nuclear ribosomal DNA internal transcribed spacer regions (ITS1-5.8S-ITS2 = ITS), the D1/D2 domain of the large subunit nrDNA (28S), and a portion of the translation elongation factor 1 alpha gene (TEF-1α). For amplification of these regions, the primer combinations employed were: ITS1F/ITS4 for ITS (White et al. 1990, Gardes & Bruns 1993), LR0R/LR5 for 28S (Vilgalys & Hester 1990, White et al. 1990), and EF1-983/EF1-1567R for TEF-1α (Rehner & Buckley 2005), respectively. The PCR optimization was according to Hussain et al. (2024a) and the PCR amplicons were sent to Macrogen Inc. © (Seoul, Republic of Korea) for purification and sequencing in both directions using the same amplification primers. The two reads were assembled using BioEdit v. 7.0.9 (Hall 1999) and the consensus sequences were deposited at GenBank.

Sequence alignment and phylogenetic analyses

Phylogenetic analyses were performed on two different datasets. First, a combined ITS-28S-TEF-1α dataset was constructed using sequences from 39 specimens of the suborder Plutineae (including Lepista panaeolus KUN-HKAS 105370 from suborder Tricholomatineae as the outgroup taxon) following Vizzini et al. (2024) – see Vizzini et al. (2024) for GenBank accession numbers of included sequences. This dataset mainly shows that the two species V. darbatica and V. sathei (the 3rd V. cubensis not included in the combined dataset) found in Oman belong to genus Volvariella. Second, the ITS dataset with 71 sequences of Volvariella plus the outgroup taxon Cantharocybe virosa (SDBR-CMUNK0280), was assembled to study the evolutionary relationships between species in the genus Volvariella (Caballero et al. 2025). Both datasets were constructed with sequences employed in recent phylogenetic studies of Volvariella and Plutineae (Malysheva et al. 2019, Chattopadhyay et al. 2022, Kumla et al. 2022, Haqnawaz et al. 2023, Vizzini et al. 2024, Caballero et al. 2025). The assembled datasets were aligned using MAFFT v. 7 (Katoh et al. 2019), and manually inspected and adjusted in BioEdit v. 7.0.9 (Hall 1999), and ClustalX v. 2.1 (Larkin et al. 2007), respectively. Files of the ITS and the combined ITS-28S-TEF-1α alignments are available online at the figshare platform (doi: 10.6084/m9.figshare.25911064).

Two different phylogenetic analyses were run, maximum likelihood (ML) and Bayesian Inference (BI). The ML analysis was executed in RAxML v. 8.2.12 (Stamatakis 2014) specifying a GTRGAMMAI model for all partitions and 1000 rapid bootstrap (BS) replicates, implemented in the CIPRES Science Gateway (https://www.phylo.org/portal2/; Miller et al. 2010). The BI analysis was done using BEAST v. 1.8.2 (Drummond et al. 2012). A Birth-Death Incomplete Sampling model was specified (Stadler 2009). Four runs were performed, each with 10 M generations. The log files were loaded in Tracer v. 1.6 (Rambaut et al. 2014) to check the values of effective sample size (ESS) for all parameters; all of these were found to be well over 200. In LogCombiner v. 1.8.2, the tree files were merged, and TreeAnnotator v. 1.8.2 was used to create a maximum clade credibility (MCC) tree (Drummond & Rambaut 2007). Statistical support values were considered significant when the ML bootstrap (BS) percentage was ≥ 70 %, and BI posterior probabilities (PPs) were ≥ 0.95. FigTree v. 1.4.2 (Rambaut 2012) was used to visualize the phylogenetic tree, which were subsequently annotated using Adobe Illustrator CC2019.

RESULTS

Phylogenetic analyses

The combined ITS-28S-TEF-1α dataset of 39 specimens of Pluteineae consisted of 1710 characters, including 996 constant sites, 601 parsimony informative sites, and 113 parsimony uninformative sites. The alignment included sequences of 38 specimens from representative species of the suborder Plutineae. There were nine species of Amanitaceae, eight of Pluteaceae, nine of Volvariellaceae, two of Limnoperdaceae, and 10 of Melanoleucaceae. Since both ML and BI analyses produced phylogenetic trees with similar topologies, only the ML is depicted (Fig. 1) with annotated with both BS and PP values.

Fig. 1.

Phylogeny of suborder Plutineae based on multigene sequence data, individual family in the suborder recovered with excellent statistical support; values above the nodes represent maximum likelihood bootstrap and Bayesian posterior probabilities.

The final ITS dataset of Volvariella consisted of 71 sequences with an alignment length of 589 characters, including 181 constant sites, 346 parsimony informative sites, and 62 uninformative sites. The dataset contained 70 different specimens of the genus Volvariella along with the outgroup taxon Cantharocybe virosa (SDBR-CMUNK0280). Phylogenetic trees resulting from the ML and BI methods were topologically similar, so only the ML tree was reproduced (Fig. 2), annotated with support values from both analyses. Species of Volvariella grouped into three major clades with good statistical support. The basal clade (V–I; V stands for Volvariella) consisted of Volvariella bombycina, V. diplasia, V. orientalis, and V. volvacea. The common morphological feature among these species is their large-sized basidiocarps. The second clade (V-II) contained V. bilobata, V. niveosulcata, V. perciliata and V. pulla. There is no common morphological feature among these species; however, brown colouration of the cap is common in V. bilobata and V. pulla (Malysheva et al. 2019, Chattopadhyay et al. 2022). Most of the species included in this study fall in the third clade (V-III). Species in V-III shared small to medium-sized basidiomata. The new species Volvariella darbatica formed an independent lineage in clade V-III with two conspecific sequences, deposited in GenBank as Volvariella sp. (KY636377 from Pakistan, MK018839 from USA). The closely related species to Volvariella darbatica are: V. cubensis, V. morozovae, V. nullicystidiata, V. ptilotricha, V. taylorii, V. cordispora, and V. izmirensis. Collection DRB2-23-001 was found to be phylogenetically similar to V. cubensis ARF-4948 from the USA. Similarly, the specimen DRB-22-005 grouped with Volvariella sathei, being related also to V. neovolvacea. The specimen DRB-22-005 seems phylogenetically different but morphologically identical to V. sathei.

Fig. 2.

The ML phylogeny of Volvariella based on 71 ITS sequences including the outgroup taxon Cantharocybe virosa (SDBR-CMUNK0280). Text on each leaf arranged in order as GenBank accession, species name, specimen’s voucher, and country of origin. Above the nodes are the values of bootstrap percentages (BS) and Bayesian Posterior Probabilities (PPs). The BS values ≥ 70 % and PPs ≥ 0.95 are shown. Species of the genus are recovered in three major clades with excellent to moderate phylogenetic support; the pink highlighted taxa in clades V–III are the specimens studied during this study.

Taxonomy

Volvariella darbatica

S. Hussain, A. Al-Owaisi, Al-Sadi & Al-Yahya’ei, sp. nov. MycoBank MB 854048. Figs 3A–C, 4.

Fig. 3.

Basidiomata of Volvariella species. A–C. Volvariella darbatica (holotype DRB-22-004), arrows in B represent the radially arranged fibrils. D–E. Volvariella sathei (DRB-22-005). F–H. Volvariella cubensis (DRB2-23-001). Scale bars = 20 mm.

Fig. 4.

Illustrations of anatomical features of Volvariella darbatica (holotype DRB-22-004). A. Basidiospores. B. Pleurocystidia. C. Basidia. D. Cheilocystidia. E. Volva elements. F. Pileipellis. Scale bars: A = 5 µm; B–D = 20 µm; E, F = 30 µm.

Etymology: The specific epithet “darbatica” refers to the locality Darbat, a tourist spot in Dhofar region, southern Oman, where the holotype was collected.

Typus: Oman, Dhofar, Wadi Darbat, 250 m a.s.l., grassland, in soil, 9 Aug. 2022, S. Hussain & Al-Yahya’ei, DRB-22-004 (holotype Mawarid DRB-22-004). GenBank accessions: ITS = PP817224, 28S = PP813713, TEF-1α = PP826251.

Description: Basidiomata small-sized. Pileus 30–40 mm diam., plano-convex to convex, pale pinkish to creamy, centre pale brownish to greyish brown, slightly umbonate at the centre, surface silky fibrillose to hairy, the fibrils aggregate into squamules that arrange in radial lines when wet, with crenate margins fringed with silky fibrils; non-hygrophanous, not viscid, membranous. Lamellae free, subdistant, broad to slightly ventricose, pinkish to pale pink, edge entire and concolourous to lamellae, with 0–1 layer of lamellulae. Stipe 40–50 × 2–3 mm, central, equal, white, smooth. Annulus absent. Volva thin, membranous, saccate, greyish brown, irregularly lobed, outer surface smooth. Odour and taste not recorded. Basidiospores (4.7–)5.0–6.0(–6.2) × (4.2–) 4.5–5.0 (–5.2) µm, (= 5.5 ± 0.23 × 4.8 ± 0.24 µm, Qm = 1.3, n = 50), in front view broadly ellipsoid to ovoid, in side view ellipsoid to broadly ellipsoid, hyaline in KOH, thick-walled, smooth, germ-pore absent. Basidia 22.0–26.0 × 7.5–9.5 µm, clavate to broadly cylindrical, hyaline in KOH, 4-spored. Cheilocystidia 50.0–62.0 × 20.0–28.0 µm, clavate to broadly fusiform, thin-walled, hyaline in KOH. Pleurocystidia 50.0–62.0 × 20.0–28.0 µm, ellipsoid to clavate or utriform, thin-walled, hyaline. Lamellar trama convergent, consisting of thin walled, hyaline hyphae, measuring 7.0–12.0 µm diam. Pileipellis a cutis, consisting of short, cylindrical elements, each 15.0–18.0 µm diam., terminal elements with rounded ends, each measuring 50.0–75.0 × 15.0–18.0 µm, hyaline to pale in KOH. Volva is arranged as an irregular trichoderm, made up of branched hyphae with terminal elements clavate to cylindrical or subglobose, greyish brown in KOH, measuring 22.0–40.0 × 11.0–22.0 µm. Clamp connection absent in all tissues.

Habitat and distribution: Saprobic on soil and woody debris. Solitary or dispersed in small groups among herbaceous plants. Distributed in West Asia (Oman), South Asia (Pakistan) and North America (USA).

Additional materials examined: Oman, Dhofar, Wadi Jarzeez, on woody debris under herbaceous plants, 5 Sep. 2023, S. Hussain & M. Al-Jahwari, JRZ2-23-021 (Mawarid JRZ2-23-021); ibid., JRZ2-23-023 (Mawarid JRZ2-23-023).

Notes: Volvariella darbatica is characterized by its small-sized and slender basidiomata with pale creamy to pale brownish and fibrillose pileus, greyish brown and membranous volva, and its small (5.0–6.0 × 4.5–5.0 µm) and broadly ellipsoid to ovoid basidiospores. On the basis of the BI and ML analyses of the ITS region, the most similar species to Volvariella darbatica are: V. cubensis, V. morozovae, V. ptilotricha, and V. taylorii. Volvariella cubensis is a neotropical species, distributed in South America, Central America and South Asia (Shaffer 1957, Pegler 1983, Wartchow 2009, Farook et al. 2013, Hernández-Del Valle et al. 2019). In the present study the distribution of V. cubensis is further extended to West Asia (Oman). This species has huge basidiomata very different from that of V. darbatica, with a pileus up to 116 mm diam., an olive grey colouration of fibrils, and larger basidiospores (5.5–7.5 × 4.5–6 µm; Hernández-Del Valle et al. 2019). Volvariella ptilotricha is a recently described species, only known from the type locality in Vietnam, characterized by its remarkably small basidiomata with a pileus about 5–15 mm diam., fibrillose cap surface, fibrils sandy grey to brownish, and olive grey volva (Malysheva et al. 2019). Volvariella morozovae is another small-sized species only reported from Vietnam, which differs from V. darbatica by its greyish to blackish fibrillose pileus surface (Crous et al. 2017, Malysheva et al. 2019). Volvariella izmirensis is a recently reported species from Turkey, characterized by small to medium-sized basidiomata, with whitish pileus with cinereous centre, golden brown to ochre brown saccate volva, mainly narrow fusiform to fusiform pleurocystidia with an elongated neck, and larger basidiospores measuring 6.8–9.5 × 4.2–5.4 µm (Caballero et al. 2025). Volvariella cordispora is another small-sized species, characterized by whitish pileus with pale brown veil remnants at the centre, and a characteristic heart-shaped basidiospores (Caballero et al. 2025). Volvariella taylorii is a medium-sized, greyish coloured species, with saccate volva and large cystidia, found in coastal region, widely distributed species in Europe (Boekhout 1990). Several studies have reported this species outside Europe, such as from North and South America (Shaffer 1957), and Asia (Seok et al. 2002, Khan et al. 2021). In most of these reports the species reported as V. taylorii turned out to be a different species following molecular phylogenetic analysis (Caballero et al. 2025). For example, a collection HUP-10388 (GenBank accession MW683932) which was recently reported from Pakistan as V. taylorii (Khan et al. 2021) is actually V. sylvipraticola (Caballero et al. 2025). This could be the reason that specimens of V. taylorii cluster in different clades in the phylogeny of Volvariella.

Volvariella sathei

Senthil. et al., Mycotaxon 119: 470. 2012. Figs 3D–E, 5.

Fig. 5.

Illustrations of anatomical features of Volvariella sathei (DRB-22-005). A. Basidiospores. B. Basidia. C. Pleurocystidia. D. Cheilocystidia. E. Pileipellis. F. Volva elements. Scale bars: A = 5 µm; B–D = 20 µm; E, F = 40 µm.

Description: Basidiomata medium to large-sized. Pileus 60–90 mm diam., convex to hemispheric, yellowish brown to whitish, surface covered with shiny yellowish fibrils, with radial striations towards the margin, margins thin, slightly eroded. Lamellae free, broad to ventricose, pinkish to pinkish brown, crowded, with 0–3 layers of lamellulae. Stipe 70–100 × 7–10 mm, central, equal, cylindrical, solid, surface creamy to white, glabrous. Annulus absent. Volva free, irregularly lobed, thick, inner surface white and glabrous, outer surface greyish and glabrous. Odour pleasant when fresh, pungent when dry, taste not recorded. Basidiospores (5.5–)6.0–7.0(–7.5) × (5.2–)5.5–6.5(–7.0) µm, [= 6.5 ± 0.26 × 4.8 ± 0.25 µm, Qm = 1.1, n = 50], in face view subglobose to rounded triangular or heart-shape, in side view broadly obovoid to broadly pyriform, hyaline in KOH, slightly thick-walled, germ-pore absent, apiculus visible. Basidia 22.0–33.0 × 7.0–10.0 µm, clavate to cylindrical, 4-spored. Cheilocystidia 66.0–96.0 × 18.0–38.0 µm, narrowly fusiform to fusiform, abundant, hyaline in KOH, smooth. Pleurocystidia 76.0–110.0 × 25.0–54.0 µm, broadly fusiform to broadly utriform, hyaline in KOH. Lamellar trama convergent, consisting of thin-walled hyaline, 5.0–18.0 µm diam hyphae. Pileipellis a cutis, consisting of thin-walled hyphae 7.5–11 µm diam., rarely branched, pale yellowish in KOH. Volva arranged as a cutis composed of unbranched hyaline hyphae, up to 15 µm diam., with terminal elements cylindrical to clavate, each measuring 90–160 × 12–15 µm. Clamp connections absent from all tissues.

Habitat and distribution: Volvariella sathei is a rare subtropical species, previously known only from the type locality, Pune, Maharashtra State, India (Senthilarasu et al. 2012). This is the second report of this species outside of India. However, V. cf. sathei, a similar taxon has been reported from Niger, Africa (Daniëls et al. 2015).

Material examined: Oman, Dhofar, Wadi Darbat, 250 m a.s.l., on soil under grasses, 9 Aug. 2022, S. Hussain & Al-Yahya’ei, DRB-22-005 (Mawarid DRB-22-005). GenBank accessions: ITS = PP853269, 28S = PP820531.

Notes: Volvariella sathei is a medium to large-sized mushroom in the Volvariellaceae. The genus contains some important edible species, such as Volvariella volvacea which is called paddy straw mushroom. However, the edibility of Volvariella sathei has not been tested, it is therefore recommended not to consume it. It is extremely important to investigate the nutritional and biochemical properties of this mushroom to avoid poisonings.

Volvariella cubensis

(Murrill) Shaffer, Mycologia 49: 564. 1957. Figs 3F–H, 6.

Fig. 6.

Illustrations of anatomical features of Volvariella cubensis (DRB2-23-001). A. Basidiospores. B. Basidia. C. Cheilocystidia. D. Pleurocystidia. E. Pileipellis. F. Volva elements. Scale bars: A = 5 µm; B–D = 20 µm; E, F = 40 µm.

Description: Basidiomata medium to large sized. Pileus 60 mm in diam., convex to hemispheric with umbonate centre, covered with radially arranged silky fibrils, fibrils pale greyish towards the periphery, dark greyish at centre, with entire margins. Lamellae free, cream to pinkish, broad, crowded with 0–2 layers of lamellulae, lamellar edge even. Stipe 55 × 5 mm, central, broader towards the base, whitish, smooth. Annulus absent. Volva fleshy, irregularly lobed, smooth, greyish brown. Odour and taste not recorded. Basidiospores (5.5–)6.0–7.0(–7.5) × (3.5–)4.0–4.5(–5.0) µm, (= 6.5 ± 0.28 × 4.3 ± 0.20 µm, Qm = 1.5, n = 55), in front view broadly ellipsoid to amygdaliform or ovoid, in side view ellipsoid, hyaline to light green in KOH, smooth, thick-walled, apiculus visible, germ-pore absent. Basidia 15.5–22.0 × 7.5–10.0 µm, cylindrical to clavate, hyaline in KOH, 2- to 4-spored. Cheilocystidia 37.0–50.0 × 13.0–20.0 µm, utriform to broadly utriform, hyaline in KOH, thin-walled. Pleurocystidia 45.0–75.0 × 15–23.5 µm, utriform to clavate, hyaline in KOH, thin-walled. Lamellar trama convergent, consisting of thin-walled hyaline hyphae measuring 7–10 µm diam. Pileipellis an intricate trichoderm to irregular trichoderm, rarely branched, consisting of cylindrical elements with up to 15 µm in diam., terminal elements cylindrical to clavate, pale greyish in KOH, measuring 40.0–76.0 × 11.5–17.5 µm. Volva is arranged as trichoderm, consisting of branched hyphae, pale greyish to pale brownish in KOH, terminal elements clavate to fusiform with rounded end, measuring 47.5–69.0 × 14.5–18.0 µm. Clamp connection absent in all tissues.

Habitat and distribution: Volvariella cubensis is a rarely reported species, distributed in South America, Central America, and India (Shaffer 1957, Pegler 1983, Wartchow 2009, Farook et al. 2013, Hernández-Del Valle et al. 2019). In the present study, the known distribution of the species is extended to include West Asia, the Arabian Peninsula.

Material examined: Oman, Dhofar, Wadi Darbat, 250 m a.s.l., on trunk of Ficus tree, 2 Sep. 2023, S. Hussain & Al-Jahwari, DRB2-23-001 (Mawarid DRB2-23-001). GenBank accession: ITS = PP853270.

Notes: Volvariella cubensis is a medium to large-sized mushroom, characterized by greyish silky fibrillose pileus surface. The specimen we studied is morphologically similar to the published descriptions of Volvariella cubensis (Shaffer 1957, Pegler 1983, Wartchow 2009, Farook et al. 2013, Hernández-Del Valle et al. 2019). Using ML phylogenetic analysis of the ITS region, the sequence obtained from the Omani collection seems identical to other identified as V. cubensis (GenBank OP580290).

DISCUSSION

Volvariella is an important mushroom genus present in tropical, subtropical, and temperate regions (Shaffer 1957, Pegler 1977, Kirk et al. 2008, Li et al 2009, Niego et al. 2021). Currently, the species identification of Volvariella is based on both morphological characters of basidiomata and molecular phylogenetic analyses of different DNA regions, including ITS, 28S, and TEF-1α (Justo & Castro 2010, Justo et al. 2011, He et al. 2019, Malysheva et al. 2019, Niego et al. 2021, Kumla et al. 2022). Morphologically, species of Volvariella are characterized by pluteoid basidiomata (free lamellae, context of the pileus discontinuous with context of the stipe, stipe usually longer than pileus), pinkish brown spore-print, and a saccate volva at the stipe base (Justo et al. 2011, Caballero et al. 2025). The taxonomic keys of the genus are mainly based on colour of basidiomata, size of pileus, lignicolous/terrestrial habitat, and basidiospore morphology (Shaffer 1957, Caballero et al. 2025). In the present study, we reported one new species and two first records of Volvariella species from Oman. Volvariella darbatica is a terrestrial species sporulating under grasses, characterized by a small-sized basidiomata, whitish to creamy fibrillose pileus surface, brownish membranous volva, and broadly ellipsoid to ovoid basidiospores (5.0–6.0 × 4.0–4.5 µm). There are several species in the genus with similar morphology and related habitat. For example, V. cordispora is a small-sized species with whitish basidiomata, sprouting under disturbed habitat, with globose to heart-shaped basidiospores measuring 5.0–8.1 × 3.8–5.2 µm (Caballero et al. 2025). Volvariella alba is a small-sized, whitish species, with volva (15 mm in length) almost half of the size of stipe (20–30 mm in length), and was recently reported from Southern Pakistan on soils with a deserted habitat (Jabeen et al. 2025). Volvariella pusilla is a European species found mostly in lawns and gardens, and occasionally in forest floor, basidiomata small-sized, whitish, with 2–3 lobed membranaceous, saccate volva (Caballero et al. 2025). Volvariella reidii is small-sized, whitish at the young stage, pale pinkish at the old stage, found on the forest floor of gymnosperms (Heinemann 1978). Volvariella globifera, a recently reported species from Spain, with whitish, small-sized basidiomata, with broadly ellipsoid to oblong basidiospores (4.6–7.3 × 3.3–4.6 μm), sporulates on sandy soil under Cupressus macrocarpa (Caballero et al. 2025). Volvariella pilosipilea might be the smallest species in the genus with a pileus diameter of 6–11 mm, both cap and volva are delicate, whitish and translucent (Caballero et al. 2025).

Some species of Volvariella are sporulating in association with other mushrooms. Volvariella terrea is a small to medium-sized species, characterized by having a tomentose-lanose pileus surface, growing under broad-leaved trees, with ellipsoid to cylindrical basidiospores measuring 5.9–9.9 × 3.8–5.6 µm (Caballero et al. 2025).

The two species Volvariella neovolvacea and V. sathei share a clade with strong phylogenetic support. Both are phylogenetically closely related, but morphologically easily distinguishable. Volvariella sathei is a whitish, medium to large-sized species, found on soil under trees with grasses, basidiospores globose to subglobose, measuring 6.0–6.5 × 5.0–5.5 µm (Senthilarasu et al. 2012, Daniëls et al. 2015). Volvariella neovolvacea is a recently reported species from Thailand, growing on soil in grasslands, with medium-sized basidiomata, brownish orange to greyish brown pileus, ellipsoid to broadly ellipsoid basidiospores, measuring 6.7–7.5 × 5.2–5.5 µm (Kumla et al. 2022).

The systematic position of Volvariella has changed multiple times. Due to the presence of a volva it was included in Amanitaceae (Lee et al. 1959), while the pinkish spore-print was the basis to transfer it to Agariaceae (Lee 1973), and finally, it was placed in Pluteaceae based on its morphology similarity to Pluteus (Singer 1986). Molecular phylogenetic analyses suggested that Volvariella is related to Cantharocybe and Cuphophyllus in the family Hygrophoraceae (Justo et al. 2011). Other studies failed to place Volvariella in any family and treated it as incertae sedis (Niego et al. 2021, Kumla et al. 2022). Recently, an updated phylogeny of Agaricales was constructed with six genes, where Volvariella was placed in a newly erected family Volvariellaceae in the suborder Pluteineae (Vizzini et al. 2024). The present results confirm that Volvariella does not belong to the other families of Pluteineae, a result found in many previous studies.

Conflict of Interest:

The authors declare that they have no conflict of interest.