Pseudotomentella umbrinascens Svantesson

Svantesson, Sten, Larsson, Karl-Henrik, Koljalg, Urmas, W. May, Tom, Patrik Cangren,, Henrik Nilsson, R. & Larsson, Ellen, 2019, Solving the taxonomic identity of Pseudotomentellatristis s. l. (Thelephorales, Basidiomycota) - a multi-gene phylogeny and taxonomic review, integrating ecological and geographical data, MycoKeys 50, pp. 1-77 : 49-50

Pseudotomentella umbrinascens Svantesson sp. nov. Fig. 19

Type.

SWEDEN. Bohuslän: Tanum (municipality), Tanum (parish), Greby Kleva, boreonemoral, deciduous forest on soil with high pH, RT90: E1236840, N6518916, 6 September 2016, S. Svantesson 335 (holotype: GB!, GenBank Acc. No. ITS: MK290697)

UNITE SH.

SH030563.07FU

Etymology.

The name refers to the overall morphological similarity to P. umbrina .

Description.

Basidiome annual, resupinate, membranaceous, effused to approximately ten centimetres in diameter. Mature parts continuous, with a cottony texture when fresh and a rather firm, fibrous and compact, yet quite soft and elastic texture when dried. Hymenium smooth; greenish-brown when fresh, pale brown when dried. Immature parts discontinuous, byssoid with a cottony texture, both when fresh and when dried. Subhymenium and hymenium of the immature parts initially yellowish-white to pale brown, in the dried basidiome, when more mature pale brown. Subiculum well developed, loose, fibrous, pale yellowish-brown to pale orange brown; forms the outer edge of the basidiome, extending noticeably beyond the hymenium.

Hyphal cords lacking, but loose bundles of subicular hyphae sometimes present.

Hyphal system monomitic, clamp connections and reaction in Melzer’s reagent absent from all hyphae.

Subicular hyphae noticeably long and straight, thick-walled; forming a loose tissue. Individual hyphae 3.1-) 3.2-4.3 (-4.8) μm wide, with a mean width of 3.7 μm; pale orange brown to brown in KOH, orange brown in water.

Subhymenial hyphae often somewhat sinuous, thin to thick-walled; forming a rather dense tissue. Individual hyphae 3.6-5.7 (-7.1) μm wide, with a mean width of 4.5 μm; pale grey brown to grey brown or brown in KOH; orange brown to pale green in water (but not with the blue green reaction present in other species), with strongly granular contents.

Encrustation not seen.

Basidia with four slightly curved sterigmata, occasionally two-sterigmate; clavate to narrowly clavate, sometimes clavopedunculate, thin-walled, with one-three slight constrictions. Dimensions: (57-) 58-71 (-75) × (8.8-) 9.5-11.5 (-12.5) μm; mean dimensions: 64 × 10.6 μm. Sterigmata 8.1-9.5 (-10.1) μm long, with a mean length of 8.6 μm. Colours and reactions the same as for the subhymenial hyphae, but in addition sometimes with granular contents in KOH.

Cystidial organs lacking.

Basidiospores in frontal face generally with a triangular or subcircular basic shape and an angular to cross-shaped or sometimes nodulose outline, covered in bi- or trifurcate, sometimes singularly attached, echinuli. Nearly all spores with three-four distinct, often rounded lobes; subcircular, five-lobed spores infrequently occurring, as well as abnormally large spores originating from two-sterigmate basidia. Frontal dimensions: (8.5-) 8.7-9.4 (-9.6) × (8.4-) 8.7-9.2 (-9.3) μm; mean dimensions: 8.9 × 8.9 μm; Q-value: 1.0 (-1.1); mean Q-value: 1.0. Echinuli (0.9-) 1.0-1.9 (-2.0) μm long, with a mean length of 1.6 μm. Lateral face ellipsoid to narrowly ovoid or sometimes semicircular in shape, usually with evenly rounded edges, sometimes with one-three lobes. Lateral dimensions: 8.5-9.2 (-9.4) × (5.7-) 6.0-6.5 μm; mean dimensions: 8.9 × 6.2 μm; Q-value: 1.3-1.5 (-1.6); mean Q-value: 1.4. Colour in KOH pale brown to pale greenish-brown colour; in water pale brownish-orange to pale greenish-orange; inamyloid.

Chlamydospores lacking.

Habitat.

The only specimen recorded to date of P. umbrinascens is the type collection, which was obtained in an old, coastal, deciduous forest on soil with high pH. UNITE sequence metadata shows that the species forms ectomycorrhiza with at least Corylus avellana ( Kõljalg et al. 2005, Nilsson et al. 2019).

Distribution.

Basidiomata encountered in: Sweden. Soil or root tip samples confirm presence also in: Italy.

Remarks.

Within the P. tristis group, basidiomata of P. umbrinascens can be recognised by their brown colour, their soft, rather elastic texture after drying and their microcharacters. Blue or green colours are completely absent from immature parts and from the subhymenium of mature parts. Pseudotomentella umbrina is very similar but has slightly different microcharacters (see key). Hypochnus rhacodium (only known from the type) is also similar but has basidiomata that are hard and brittle after drying.