Pseudotomentella tristoides Svantesson & K.H.Larss.

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 : 43

Pseudotomentella tristoides Svantesson & K.H.Larss. sp. nov. Fig. 17

Type.

NORWAY. Nord-Tröndelag: Snåsa, Bergsåsen, boreal, deciduous forest on soil with intermediate pH, 28 August 2012, K.-H. Larsson (holotype: O F110306!, GenBank Acc. No. ITS: MK290692).

UNITE SH.

SH030566.07FU

Etymology.

The name refers to the overall similarity between this species and P. tristis .

Description.

Basidiome 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. Hymenium smooth; brown with a reddish hue. Immature parts discontinuous, byssoid with a cottony texture. Subhymenium and hymenium of immature parts initially pale greyish-blue, when more mature dark blue grey. Subiculum well-developed, loose, fibrous, brown with an orange hue; forms the outer edge of the basidiome, extending noticeably beyond the hymenium. All characters recorded in dried state.

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 (4.7-) 4.9-7.1 (-7.6) μm wide, with a mean width of 6.0 μm; orange brown to dark brown in KOH, orange brown to brown in water.

Subhymenial hyphae often somewhat sinuous, thin to thick-walled; forming a rather dense tissue. Individual hyphae (3.1-) 3.2-5.3 (-5.4) μm wide, with a mean width of 4.6 μm; pale yellowish-brown in KOH, pale green to blue green in the presence of air; pale green to pale orange green in water, with strongly granular contents.

Encrustation granular, amyloid, concolourous with the hyphae in both KOH and 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 to narrowly clavate, sometimes clavopedunculate, thin-walled, with one-three slight constrictions. Dimensions: (49-) 54-72 (-75) × (7.3-) 7.9-10.0 (-10.5) μm; mean dimensions: 63 × 9.1 μm. Sterigmata (7.6-) 7.8-9.9 (-10.5) μm long, with a mean length of 8.6 μm. Colours and reactions the same as for the subhymenial hyphae.

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-five indistinct corners to distinct, square lobes; subellipsoid, ovoid and subcircular spores with a rather evenly rounded outline occasionally occurring, as well as subcircular, six-lobed spores; abnormally large spores originating from two-sterigmate basidia infrequently seen. Frontal dimensions: 7.7-8.6 (-8.8) × (7.4-) 7.7-9.3 (-9.5) μm; mean dimensions: 8.2 × 8.5 μm; Q-value: 0.9-1.1; mean Q-value: 1.0. Echinuli (0.5-) 0.7-0.9 (-1.1) μm long, with a mean length of 0.8 μm. Lateral face ellipsoid, usually with evenly rounded edges, sometimes with one-three lobes. Lateral dimensions: (7.9-) 8.0-8.6 × 6.0-6.5 (-6.7) μm; mean dimensions: 8.2 × 6.3 μm; Q-value: 1.2-1.4; mean Q-value: 1.3. Colour in KOH brown to yellow brown, in the presence of air often with a green to blue green reaction; in water pale greenish to pale greenish-orange; occasionally amyloid.

Chlamydospores lacking.

Habitat.

The only specimen recorded to date of P. tristoides is the type collection, which was obtained in an old, mixed forest on soil with intermediate pH. UNITE sequence metadata show that the species forms ectomycorrhiza with at least Populus alba and Cephalanthera damasonium ( Kõljalg et al. 2005, Nilsson et al. 2019).

Distribution.

Basidiomata encountered in: Norway. Soil or root tip samples confirm presence also in: Estonia and the Czech Republic.

Remarks.

Within the P. tristis group, the basidiome of P. tristoides can be recognised by its lack of hyphal cords and skeletal hyphae and its soft, yet rather firm and compact and ± elastic texture after drying, bluish to greenish colour of immature parts, wide subicular hyphae, medium sized, angular-nodulose spores and relatively short echinuli and sterigmata. Pseudotomentella tristis is similar but has longer echinuli and sterigmata, P. sciastra has smaller, star-shaped spores and H. rhacodium (only known from the type) has hard, brittle basidiomata after drying.