Sistotremastrum fibrillosum G. Gruhn & P. Alvarado, 2018

Gruhn, Gérald, Alvarado, Pablo, Hallenberg, Nils, Roy, Mélanie & Courtecuisse, Régis, 2018, Contribution to the taxonomy of Sistotremastrum (Trechisporales, Basidiomycota) and the description of two new species, S. fibrillosum and S. aculeocrepitans, Phytotaxa 379 (1), pp. 27-38 : 31-32

Sistotremastrum fibrillosum G. Gruhn & P. Alvarado , sp. nov. ( Figs. 3 and 4-A )

MycoBank: MB 823879

Diagnose: Differs from other Sistotremastrum species because of its fibrillose basidiome with numerous wide cords, and hymenial surface shortly odontoid and farinaceous.

Holotype: LIP 0001413

Isotypes: GB, GG GUY12-180

Etymology: fibrillosum epithet refers to the fibrillose aspect of young specimens, the margin, and the large cords running on the wood under the subiculum.

Basidiome resupinate, widely effused, up to 25 × 9 cm, loosely attached to the wood substrate, young parts white to light cream colored when fresh, mature parts becoming light ochraceous, colliculose to shortly odontoid, developing numerous (8-10 or 12/mm) thin and subulate aculei, easily separated from subiculum, 100–250(–400) μm long, × 70– 150 μm in diam. at the base. Young specimens have large white cords with scattered aculei, which are shorter and even more scattered between cords, where the structure is loose and porulose. Context porulose, cracked between aculei, 30–60 μm thick. Margin farinaceous to pulverulent, fibrillose, with fragile smooth cords, white, 200–400 μm wide, continuing into the wood substrate. Hyphal system monomitic. Hyphae in cords hyaline, agglutinated and not easy to discern, with slightly thick walls (about 0.5 μm thick), 3 (4–5) μm in diam., clamp connections present at all septa, never ampullate. Subhymenial hyphae with thin walls, 1.5–2.5 μm in diam. Core of aculei made up of undifferentiated hyphae. Hyphidia seen at the apex of aculei, filamentose, tapering, with constrictions, thin-walled, clamped at the base, hyaline, smooth, 21−30 × 3−4 μm. Basidia clavate to cylindrical, often with a median constriction, (13−)15−18 × 4.5−6 μm, with a basal clamp, sometimes stalked, frequently collapsed, and then tabular with a triangular head, always 4-sterigmate, sterigmata slender, up to 3.5 μm long. Spore print white. Basidiospores sometimes agglutinated, ellipsoid, with adaxial side flat, walls hyaline, thin, smooth, 4.5−5.5(6.0) × 2.5(3.0) μm, Qm= 2.0, non-cyanophilous, not reacting to Melzer’s reagent.

Specimens examined: FRENCH GUIANA: LIP 0001413 (holotype) and GB (isotype) and GG-GUY12-180 (isotype), 26 June 2012, Sinnamary, Saint-Élie road, Arbocel, on fallen wood of undetermined deciduous tree, leg & det G. Gruhn ; GG GUY12-028 (& GB), 17 June 2012, Régina , Les Nouragues, petit plateau, on fallen wood of undetermined deciduous tree, leg. & det. G. Gruhn ; GG GUY12-191 (& GB), 26 June 2012, Sinnamary , Saint-Élie road, Arbocel, on hardwood on the ground, leg. & det. G. Gruhn ; GG GUY13-119 (& GB), 23 October 2013, Saül , Crique Limonade, “A” Diadema track, slop zone, on unknown host, leg. & det. G. Gruhn ;

Figures

FIGURE 3. S. fibrillosum (holotype).A: spores. B: hyphidia. C: mature basidia. D: postmature basidia. bar = 10 μm.

FIGURE 4. S. fibrillosum Basidiomes, fresh material in situ. A: holotype. B: GG GUY13-119. C: GG GUY12-191.