Pseudotomentella media Svantesson & Koljalg

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 : 25-27

Pseudotomentella media Svantesson & Koljalg sp. nov. Fig. 11

Type.

ESTONIA. Valga: Otepää, Trommi, 12 September 2012, U. Kõljalg (holotype: TU 115609!, GenBank Acc. No. ITS: MK290714).

UNITE SH.

SH005336.07FU

Etymology.

The name refers to the middling morphological characters of the species, relative to other species in the P. tristis group.

Description.

Basidiomata annual, resupinate, membranaceous, effused to approximately ten centimetres in diameter. Mature parts continuous, with a rather firm, fibrous and compact, yet quite soft and elastic texture when dried. Hymenium smooth, but sometimes strongly undulating; brown with a reddish hue, both when fresh and when dried. Immature parts discontinuous, byssoid, with a cottony texture when dried. Subhymenium and hymenium of immature parts blue to greenish-blue when fresh and pale blue grey or blue grey to grey brown when dried. Subiculum well developed, loose, fibrous, pale brown to pale orange brown; forms the outer edge of basidiomata, extending noticeably beyond the hymenium.

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

Hyphal system monomitic, clamp connections absent from all hyphae.

Subicular hyphae noticeably long and straight, thick-walled; forming a loose tissue. Individual hyphae (3.6-) 3.7-5.0 (-5.4) μm wide, with a mean width of 4.1-4.6 μm; orange brown to brown in both KOH and water.

Subhymenial hyphae often somewhat sinuous, thin to thick-walled; forming a rather dense tissue. Individual hyphae (3.2-) 3.4-5.6 (-5.7) μm wide, with a mean width of 4.3-4.4 μm; pale brown, pale orange brown, pale greenish-brown or hyaline in KOH, blue green in the presence of air; orange green to brown in water, with strongly granular contents. Some subhymenial hyphae with a pink colour in water and an amyloid reaction.

Encrustation granular, probably amyloid (hard to observe due to the colour); blackish in KOH, dark blue green in the presence of air; blackish in water; scattered in occurrence on the upper parts of subhymenial hyphae and on the lower parts of basidia.

Basidia with four slightly curved sterigmata, occasionally two-sterigmate; clavate or sometimes narrowly clavate or clavopedunculate, thin-walled, with one-three slight constrictions. Dimensions: (57-) 58-84 (-87) × (8.8-) 9.6-11.8 (-12.5) μm; mean dimensions: 74-77 × 10.2-10.7 μm. Sterigmata (9.4-) 9.5-11.4 (-11.7) μm long, with a mean length of 10.0-10.8 μm. Colours and reactions the same as for the subhymenial hyphae, but in addition often with granular contents in KOH.

Cystidial organs lacking.

Basidiospores in frontal face generally with a subcircular basic shape and an angular to nodulose or sometimes cross-shaped outline, covered in bi- or trifurcate, sometimes singularly attached, echinuli. A majority of the spores with three-six indistinct corners to distinct, square lobes; unlobed subellipsoid spores infrequently occurring, as well as abnormally large spores originating from two-sterigmate basidia. Frontal dimensions: (7.8-) 8.0-9.5 × (8.3-) 8.5-9.9 (-10.1) μm; mean dimensions: 8.9-9.3 × 9.2-9.8 μm; Q-value: 0.9-1.0; mean Q-value: 1.0. Echinuli (0.8-) 0.9-1.6 μm long, with a mean length of 1.1-1.2 μm. Lateral face ellipsoid, usually with evenly rounded edges, sometimes with one-three lobes. Lateral dimensions: (8.8-) 8.9-9.6 × (6.6-) 7.0-7.9 μm; mean dimensions: 9.1-9.4 × 7.3-7.6 μm; Q-value: 1.2-1.3; mean Q-value: 1.2-1.3. Colour in KOH pale brown to brown or pale orange brown to orange brown, in the presence of air sometimes blue green; in water orange brown to brown; inamyloid.

Chlamydospores lacking.

Habitat.

P. media has been found to form ectomycorrhiza with at least Betula pendula , Larix decidua and Picea glauca ( Kõljalg et al. 2005, Nilsson et al. 2019).

Distribution.

Basidiomata encountered in: Estonia. Soil or root tip samples confirm presence also in: Canada, Italy and Russia.

Remarks.

Within the P. tristis group, the basidiomata of P. media can be recognised by their lack of hyphal cords and skeletal hyphae and their soft, yet rather firm and compact and ± elastic texture after drying, bluish to greenish colour of immature parts, narrow subicular hyphae, brown mature hymenium, long, laterally wide, angular-nodulose spores and subhymenial hyphae that are of ± the same width as the subicular hyphae. Pseudotomentella pinophila and P. pluriloba can appear similar, but the spores of P. pinophila are laterally narrower and generally star-shaped, while P. pluriloba has wider subicular hyphae, larger spores and subhymenial hyphae that are noticeably narrower than the subicular hyphae.

Additional specimens studied.

ESTONIA. Valga: Otepää, Trommi, 12 September 2012, U. Kõljalg (TU 115608*).