Pseudotomentella rotundispora 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 : 32-36

Pseudotomentella rotundispora Svantesson sp. nov. Fig. 14

Type.

SWEDEN. Västergötland: Götene, Medelplana, Eriksberg, boreonemoral, mixed forest on soil with high pH, 17 October 2016, S. Svantesson 413 (holotype: GB!, GenBank Acc. No. ITS: MK290674).

UNITE SH.

SH030562.07FU

Etymology.

The name refers to the appearance of the spores, which often have rounded or weakly pronounced lobes and comparably short echinuli.

Description.

Basidiomata annual, resupinate, membranaceous, effused - often to several tens of 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, but sometimes strongly undulating; brown to greenish-brown when fresh, concolourous when dried, but then sometimes with a red hue. Immature parts discontinuous, byssoid with a cottony texture, both when fresh and when dried. Subhymenium and hymenium of immature parts blue to blue green or grey when fresh, pale blue grey to grey blue when dried. Subiculum well developed, loose, fibrous, pale brown to pale orange brown; often 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 3.0-4.4 (-4.6) μm wide, with a mean width of 3.4-3.8 μm; brown to orange brown in both KOH and water.

Subhymenial hyphae often somewhat sinuous, thin to thick-walled; forming a rather dense tissue. Individual hyphae (2.7-) 3.0-4.6 (-6.3) μm wide, with a mean width of 3.6-3.7 μm; pale brown to brown in KOH, often with orange or green hues, blue green in the presence of air; brown to orange brown in water, with strongly granular contents; some subhymenial hyphae with a pink colour in water and an amyloid reaction in Melzer’s reagent.

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: 40-66 (-69) × 8.2-10.6 (-11.1) μm; mean dimensions: 54-60 × 8.8-9.7 μm. Sterigmata (6.6-) 7.4-11.0 (-11.5) μm long, with a mean length of 8.5-10.2 μm.

Colours and reactions the same as for the upper parts of subhymenial hyphae, but in addition often with granular contents in KOH.

Cystidial organs lacking.

Basidiospores in frontal face very variable. Generally with a subcircular basic shape and an angular, nodulose, star-shaped or occasionally cross-shaped outline, covered in bi- or trifurcate, sometimes singularly attached, echinuli. Nearly all spores with three-seven, commonly three or five, indistinct corners to distinct, usually rounded lobes; spores with angular or square lobes infrequently occurring, as well as abnormally large spores originating from two-sterigmate basidia. Frontal dimensions: (6.7-) 7.0-8.2 (-8.4) × 7.0-8.6 μm; mean dimensions: 7.5-7.6 × 7.7-7.9 μm; Q-value: 0.9-1.1; mean Q-value: 1.0. Echinuli 0.5-1.1 (-1.3) 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: 7.0-8.2 (-8.3) × (5.2-) 5.3-6.0 (-6.1) μm; mean dimensions: 7.6-7.9 × 5.6-5.7 μm; Q-value: 1.3-1.5; mean Q-value: 1.4. Colour in KOH pale brown to brown or pale orange brown to orange brown, in the presence of air sometimes with a blue green reaction; in water brown to orange brown; occasionally with an amyloid reaction.

Chlamydospores lacking.

Habitat.

Data on habitat are scarce to date, but recent Scandinavian collections have been made in old, coniferous, deciduous or mixed forests on soil with high pH. Pseudotomentella rotundispora has been found to form ectomycorrhiza with at least Castanea sp. and Populus tremula ( Kõljalg et al. 2005, Nilsson et al. 2019).

Distribution.

Basidiomata encountered in: Estonia, Norway and Sweden. Soil or root tip samples confirm presence also in: Austria, Italy and the United Kingdom.

Remarks.

Within the P. tristis group, the basidiomata of P. rotundispora 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 and short spores. The other species within the group can appear similar, but have either wider hyphae, longer spores or both.

Additional specimens studied.

ESTONIA. Lääne: Hanila, Puhtu-Laelatu Nature Reserve, Puhtu peninsula, deciduous forest with Populus , Tilia , Quercus and Picea , 11 August 2005, U. Kõljalg (TU 100138*);

NORWAY. Oslo (county): Oslo (municipality), Bygdøy, Dronningberget, mixed forest on soil with high pH, 30 September 2017, K.-H. Larsson 17682* (O);

SWEDEN. Västergötland: Götene, Medelplana, Eriksberg, boreonemoral, mixed forest on soil with high pH, 17 October 2016, S. Svantesson 393*, 394* (GB).