Volvariella ptilotricha E.F. Malysheva & A.V. Alexandrova
Index Fungorum number: IF 831059; MycoBank number: MB 831059
Basidiocarps small. Pileus 5–15 mm diam., at first broadly campanulate or conical, becoming convex to planoconvex without distinct umbo, with even, non-striate margin; non-hygrophanous; surface dry, with complex surface pubescence: radially arranged sandy grey, brownish or ash brown fibrils, thick felt of erect short white hairs on entire area, and arachnoid tangles at margin and apex; with darker centre, paler to whitish towards margin. Lamellae rather crowded to fairly distant, free, with solitary lamellulae, slightly ventricose, at first white then pinkish, with crenulate edge. Stipe 8–15 × 0.6–1 mm, cylindrical, slightly broadened downward, solid, longitudinally striate, white; surface gently tomentose to hairy. Volva spacious, thin, saccate, irregularly lobed, olive-grey or rusty brown, with arachnoid wet of white hairs on outer surface. Context white. Smell and taste indistinct. (Fig. 2)
Basidiospores [30, 1, 1] 5–6(7) × 3.5–4.5 μm (Lav = 5.5 μm, Wav = 4.0 μm, Q = 1.13–1.67, Q* = 1.39), broadly ellipsoid to ellipsoid, some slightly ovoid or subglobose, hyaline in KOH, thick-walled. Basidia 16.5–24 × 7.5–9 μm, 4-spored, broadly clavate. Cheilocystidia 30–46.5 × 10–20 μm, rather numerous, predominantly utriform and lageniform, rare clavate, pedicellate, with short neck, thin-walled, hyaline in 3% KOH. Pleurocystidia 33–48 × 14–23.5 μm, abundant, mainly clavate, occasionally utriform, often septate, thin-walled, hyaline in 3% KOH. Lamella trama composed of hyaline hyphae 3–7 μm wide, thin-walled. Pileipellis a cutis, made up of slightly thick-walled, nongelatinous, hyaline or yellowish, repent or somewhat ascending hyphae, 8–15 μm wide; terminal elements cylindrical. Stipitipellis a cutis, similar to pileipellis; hairs of stipe cylindrical, hyaline, thin-walled, 100–200 μm long and 5.5–7 μm wide. Clamp connections absent in all tissues examined. (Fig. 3)
Habitat and known distribution: Solitary, on fallen trunk in tropical forest. So far only known from the type locality.
Specimen examined: VIETNAM. Province Dong Nai: Tan Phu District, Cat Tien National Park, N 11.447402°, E 107.436792°, tropical palm forest, on fallen trunk of unknown tree, 6 December 2012, A. Alexandrova 313324 (holotype LE!; GenBank MK882997 - ITS, MK940805 - tef1).
Notes: Volvariella ptilotricha is characterized by strongly pubescent basidiocarps with a rather complex pattern of pubescence. Among other small-sized representatives of the genus Volvariella, none of the known species possesses the above combination of macro and microscopic characters and, on the basis of these, they can be easily distinguished from V. ptilotricha. Volvariella villosovolva (Lloyd 1899: 31) Singer (1949: 401) is similar to the new species in having greyish pileus, volva covered with long arachnoid hairs and broadly ellipsoid to ovoid basidiospores of similar size (av. 6.1–6.4 × 4–4.4 μm), but its basidiocarps are larger than those of V. ptilotricha, pileus not pubescent, volva is white and hymenial cystidia fusoid-ventricose (Shaffer 1957). Volvariella murinella has larger basidiocarps without such a strong pubescence which is characteristic for the new species, slightly longer (5.5–8.5 μm) basidiospores, significantly larger cheilo- and pleurocystidia, and terrestrial habitat (Boekhout 1990). On the ITS-LSU phylogenetic tree (Fig. 1) the new species is grouped in one clade together with Volvariella sp. from Pakistan (voucher S42). However, their nrITS sequences differ by 10.8%, and V. ptilotricha can be considered as a separate taxon.
Fig. 1 Best tree from the ML analysis of the nrITS-nrLSU data set for Volvariella with Cantharocybe gruberi as outgroup. Bootstrap support values and Posterior probability (BS/PP) are given above the branches. All tips are labelled with taxon name and voucher ID. For taxa in bold the sequences are generated in present study.
Fig. 2 Immature and mature basidiocarps of Volvariella ptilotricha (LE 313324, holotype, photos by A. Alexandrova). Scale bars = 5 mm.
Fig. 3 Microscopic features of Volvariella ptilotricha (LE 313324, holotype). A. Pileipellis. B. Spores. C. Cheilocystidia. D. Basidia. E. Pleurocystidia. Scale bars = 10 μm.
Malysheva, E., Malysheca, V., Alexandrova, A. & Morozova, O. 2019 –Observations on Pluteaceae in Vietnam. 1. New species and new records of Volvariella. Phytotaxa 408(40): 233–254.
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