Pluteus aesontiensis Ferisin, Justo & Dovana, 2022

Dovana, Francesco, Justo, Alfredo & Ferisin, Giuliano, 2022, Pluteus aesontiensis (Agaricales, Pluteaceae) a new species in sect. Celluloderma, Phytotaxa 533 (2), pp. 149-157 : 150-153

Pluteus aesontiensis Ferisin, Justo & Dovana , sp. nov. Figs. 2–3

MycoBank no.: MB841413

Etymology:—Refers to an ancient name for the Isonzo river that flows near the growth site of P. aesontiensis .

Diagnosis:— Pluteus aesontiensis is characterized by small-sized basidiomes with brown, red-brown to deep yellowish brown pileus darker in the centre; cylindrical, sub-bulbous, white pubescent stipe; globose to ellipsoid spores, a hymenidermal pileipellis composed of typically sphaeropedunculate to clavate terminal elements; utriform to broadly fusiform cheilocystidia, fusiform to broadly fusiform pleurocystidia, and caulocystidia only in the upper part of the stipe.

Holotype:— ITALY. Farra d’Isonzo, Isonzo ( Soca ) river, on trunks of broadleaved tree (trees present in the area: Fraxinus angustifolia Vahl , Populus spp ., Robinia pseudoacacia L., Salix spp . and Ulmus minor Mill. ) on the ground, 17 June 2017, G. Ferisin; Holotype MCVE30112 !; GenBank: MZ412508 .

Description: —Pileus 20–30 mm diam., at first convex or broadly conical, then applanate to plano-concave, nonumbonate to sub-umbonate, margin translucently striate or sulcate; brown (2.5 Y5/2–5/4), red-brown (10YR 3/2–3/4– 3/6) to deep yellowish brown (2.5Y 4/2–4/4–4/6), darker at centre (10YR 2/4–1/2); surface glabrous and rugulose at centre, sometimes with irregular cracks in surface that reveal whitish flesh, non-hygrophanous. Lamellae free, crowded, up to 4 mm broad, thin, whitish in youth, later pink with flocculose edge. Stipe 25–40 × 2–3 mm, cylindrical, sub-bulbous, pubescent, white all over. Context in pileus and stipe white. Smell indistinct, taste not recorded.

Basidiospores [160/4/4](5.5–)6.1–6.6–7.1(–7.8)×(4.6–)5.0–5.6–6.2(–7.2)µm,Q=(1.00–)1.10–1.18–1.26(–1.34), subglobose to broadly ellipsoid, rarely globose or ellipsoid, guttulate, hyaline, smooth, thick-walled, cyanophilous, and inamyloid. Basidia 22–27 × 8–10 µm, clavate, 4-spored, hyaline, with granular contents. Pleurocystidia 50– 75 × 18–34 µm, thin-walled; variable in shape from fusiform to broadly fusiform with round apex, rarely obovoid, hyaline or with oily contents observed in ammonia solution. Cheilocystidia 50–80 × 20–34 µm, variable in shape from utriform, broadly fusiform with round apex to clavate or ovoid, with oily contents. Pileipellis a hymeniderm made up of sphaeropedunculate to clavate elements, 40–70 × 25–38 µm, with light brown to brown intracellular pigment. Stipitipellis a cutis of cylindrical, 4–10 µm wide, light brown hyphae. Caulocystidia 40–60 × 18–22 µm, clavate, in small clusters, in the apical part of the stipe. Clamp connections absent in all examined structures.

Habit, habitat and distribution:—In groups, on broadleaved trees (trees present in the area: ashes, black-locust, elm, poplar and willow trees). So far, it is known only from northeastern Italy.

Additional collections examined of P. aesontiensis :— ITALY. Farra d’Isonzo , 04 July 2015, G. Ferisin ( MCVE 31601!, GenBank MZ 412509 ); ibid. 17 June 2017, G. Ferisin ( FG1706201714 !, GenBank: MZ 412507 ); ibid. 06 July 2017, G. Ferisin ( FG0607201710 !, GenBank: MZ 412506 ) .

Figures

FIGURE 2. Pluteus aesontiensis. Fresh basidiomes. A Holotype- MCVE 30112. B Coll. MCVE 30113. C Coll. FG0607201710. Photos by G. Ferisin.

FIGURE 3. Pluteus aesontiensis (holotype). Micromorphological features. a Pileipellis. b Spores. c Cheilocystidia. d Pleurocystidia. Bars:10 μm. Photos by G. Ferisin.