Rhodocybe mellea var. depressa M.D. Xavier, Silva-Filho & Wartchow, 2022

Xavier, Miguel D., Silva-Filho, Alexandre G. S., Wartchow, Felipe & Baseia, Iuri G., 2022, Fine-scale diversity in Rhodocybe mellea (Entolomataceae, Basidiomycota), with a description of a new variety and notes on sclerotia formation in Rhodocybe, Phytotaxa 538 (2), pp. 87-99 : 92-94

Rhodocybe mellea var. depressa M.D. Xavier, Silva-Filho & Wartchow var. nov. ( Figs. 2–4 )

MycoBank:—MB 842858.

Type:— BRAZIL. Paraíba, Mamanguape, Reserva Biológica Guaribas , SEMA II, 23 July 2019 , F. Wartchow, FW 08/2019 (holotype UFRN-Fungos 3386!; isotype JPB)

Diagnosis:— Rhodocybe mellea var. depressa is distinguished by its depressed pileus; the presence of abundant and conspicuous sclerobasidia; small, flexuous-cylindrical pseudocystidia; pileipellis a smooth two-layered cutis; sandy soil habitat; and unique nuclear ITS and LSU sequences.

Description:—Basidiomata collybioid( Fig.2a ). Pileus 13−35 mm broad, convex with a depressed center, becoming plane and depressed, brownish orange ( OAC 729), paling to yellowish orange ( OAC 791); surface dry, hygrophanous; margin entire to slightly sulcated, decurved to straight, sometimes lobed; context fleshy, 1 mm thick, cream ( OAC 791), unchanging. Lamellae adnexed with a decurrent tooth, moderately close to close, cream-orange ( OAC 717); 2−4 mm broad, margin slightly eroded to wavy, concolorous with sides; lamellulae of varying lengths. Stipe 21−30 × 2−7 mm, equal to slightly enlarged at the base, terete when young, becoming compressed, sometimes slightly flexuous, cream-orange ( OAC 717); surface dry, smooth to slightly pruinose; consistency cartilaginous; context solid, fibrous, dark cream ( OAC 793); spore print not obtained; odor and taste not determined.

Basidiospores 5.2−6.5 × 4.1−5.4 (5.8 ± 0.30 × 4.7 ± 0.28 μm), E = (1.05)1.12−1.38, Q = 1.25, n = 60/2, subglobose to broadly ellipsoid, very rarely globose in profile view, angular in polar view with 7–9 angles, undulate-pustulate in all views, lacking a suprahilar plage, thin-walled, hyaline ( Figs. 3b – 4a ). Basidia 22.4−30 × 7.4−8.1 μm clavate, 4-spored, thin-walled, hyaline, some with yellowish contents in KOH 5%; sterigmata 4.5−5 μm long; sclerobasidia abundant, 4-spored, broadly clavate, 23.6−34.4 × 5.1−8.1 μm, with walls up to 1.2 μm thick ( Figs. 3a,c ; 4b ). Pleurocystidia as pseudocystidia 26.5−41 × 5.2−7.3 μm, originating from the subhymenium, mostly not conspicuously projecting from hymenium, flexuous-cylindrical with rounded to aculeate apex, thin-walled, with pale yellow amorphous contents in KOH 5% ( Figs. 3a – 4c ). Lamellae edge mixed composed of a few basidia and abundant pseudo-cheilocystidia, similar to the pseudo-pleurocystidia. Subhymenium ramose. Lamellar trama regular, composed of cylindrical hyphae, 4.1−7.3 μm wide, thin-walled, hyaline; oleiferous hyphae present, abundant. Pileus trama subregular, composed of cylindrical hyphae, 3.3−6.1 μm wide, hyaline, thin-walled and smooth; oleiferous hyphae present, abundant, 2.3−3.7 μm wide. Pileipellis a cutis composed of two layers, golden yellow in KOH 5% ( Fig. 3d ): suprapellis as a more separate layer with cylindrical entangled periclinal hyphae, thin-walled, smooth, and cylindrical-clavate terminal hyphae with rounded to inflated apex, 2.5−3.1 μm wide ( Fig. 4d ); subpellis a layer with strongly entangled periclinal hyphae, thin-walled and smooth. Stipitipellis a cutis of parallel hyphae, 3.6−6.4 μm wide, thin-walled to slightly thick-walled, and smooth. Caulocystidia absent. Clamp connections absent in all examined tissues.

Etymology:—The name ‘ depressa ’ comes from the Latin and refers to the depressed pileus.

Habitat:—Saprotrophic, gregarious, growing on sandy soil among leaf litter. Coastal tableland landscape with Brazilian Savanna (Cerrado) vegetation ( Fig. 2b ).

Distribution:—Known only from the type locality.

Material examined:—The type.

Figures

FIGURE 2. Photographs of the habitat and fresh basidiomata of Rhodocybe mellea var. depressa (holotype UFRN-Fungos 3386). a Basidiomata. b Coastal Tableland, Savanna vegetation. Scale bars: 10 mm. Photos by J.O. Sousa and F. Wartchow.

FIGURE 3. Rhodocybe mellea var. depressa microscopic features (holotype UFRN-Fungos 3386). a From L–R: Sclerobasidia, basidia and pseudocystidia. b Basidiospores. c Sclerobasidia. d Pileipellis. a, b and d: in KOH 5%; c: stained in Congo Red. Scale bars: 5 μm. Photos by M.D. Xavier.

FIGURE 4. Rhodocybe mellea var. depressa microscopic features (holotype UFRN-Fungos 3386). a Basidiospores. b Basidia and sclerobasidia. c Pseudocystidia. d Pileipellis: suprapellis structure and terminal hyphae. Scale bars: 5 μm. Drawings by A.G.S. Silva- Filho.