Russula capillaris Buyck, 2019

Wang, Xiang-Hua, Das, Kanad, Bera, Ishika, Chen, Yu-Hui, Bhatt, Rajendra Prasad, Ghosh, Aniket, Hembrom, Manoj Emanuel, Hofstetter, Valérie, Parihar, Arvind, Vizzini, Alfredo, Xu, Tai-Min & Zhao, Chang-Lin, 2019, Fungal Biodiversity Profiles 81 - 90, Cryptogamie, Mycologie 20 (5), pp. 57-95 : 79-83

88. Russula capillaris Buyck , sp. nov.

( Figs 16-18 )

Well-characterized by the combination of its medium-sized, firm stature, white and hard stipe, smooth and cream to pale yellowish brown pileus, nearly globose spores, (6.9)7.13-7.48-7.8(8.1) - (6.4)6.6-6.95-7.2(7.5) Μm, Q = (1.03)1.05-1.08-1.11(1.13), with very low, dense spore ornamentation of minute warts and invisible suprahilar spot, a pileipellis composed of ascending, slender, irregularly wavy-undulate hyphal extremities that are often inflated at the tip, submerged pileocystidia, pale spore print and slightly unpleasant smell, as well as by its habitat in tapia ( Uapaca bojeri ) woodland on the Central Plateau in Madagascar.

TYPUS. — Madagascar. Central Plateau, along RN7 between Antsirabe and Ambositra , at km 40, in secondary Uapaca bojeri woodland with Pinus ingression, 26.I.2008, 563/ Buyck 08.172 ( PC [ PC0124764 ]).

MYCOBANK. — 832120.

GENBANK. — MK929284 ( ITS), KU237553 ( LSU), KU237399 (mitSSU), KU237839 ( RPB2 ), KU237982 (tef1alpha), all from holotype.

ETYMOLOGY. — named after the resemblance of the pileipellis structure with a nice hair cut.

DESCRIPTION

Basidioma

Growing single, medium-sized.

Pileus

83 mm diam., quite regular in shape to slightly wavy near the margin, hardly depressed in the center, not becoming deeply infundibuliform, smooth near margin; surface glabrous, hardly separable, not viscid, probably even not when wet, continuous and smooth in the pileus center, dull, pale-colored, from whitish to cream or pale yellowish to pale yellowish brown, not concentrically zonated, not particularly darker in the center.

Gills

Adnate, with frequent lamellulae but less than normal gills, not or rarely forking, c. 6-7 mm high, thin and fragile, normally spaced (c. 1L+l/mm), pale yellowish; gill edge even, concolorous.

Stipe

Central, 43 × 16 mm, not annulate, subcylindrical, longitudinally wrinkled, glabrous, off-white, surprisingly hard and firm considering the interior is developing up to four cavities.

Context

Firm, fleshy, c. 9 mm thick above gill attachment to stipe, whitish, unchanged when cut, in the stipe with a faint creamish-pinkish tinge.

Taste

Not observed.

Odor

Faintly disagreeable.

Spore print

Unsufficient, obviously pale.

Spores

Globose to subglobose, (6.9)7.13-7.48-7.8(8.1) × (6.4)6.6- 6.95-7.2(7.5) Μm, Q = (1.03)1.05-1.08-1.11(1.13); ornamentation consisting of a minute, dense, granular-reticulate pattern, <0.1-0.2 Μm high and weakly amyloid; suprahilar spot invisible; apiculus very short and small.

Basidia

Slender, widest in their upper part, 53-61 × 8-10 Μm, fourspored; sterigmata rather slender, approximately 7 × 1-2 Μm.

Hymenial gloeocystidia

Very abundant (c. 4000/mm2), thin-walled or nearly so, not strongly emergent, on the gill sides, 60-90 × 8-9 Μm, fusiform to subclavate or almost cylindrical, frequently distinctly inflated at the apex and widely capitate (often wider than the rest of the cystidium), some also tapering, near the apex obtuse-rounded or more frequently minutely mucronate, containing poor contents in the form of dispersed, refringent masses or conglomerates; the basal part of the cystidia often sheathed with encrusting material; near the gill edge distinctly smaller and mostly simply clavate to almost subcylindrical, 34-46 × 6-7(-8) Μm, and then nearly subcylindrical to clavulate, obtuse rounded at the tip, filled with more abundant, granular-crystalline contents, weakly reacting to SV.

Subhymenium

Dense, composed of cells that are hardly wider than the basal parts of the basidia.

Lamellar trama

With sphaerocytes, rather dense.

Marginal cells

Well-differentiated, thin-walled, smaller than basidia, consisting of a basal or stalk cell holding a terminal fusiform, clavate or lageniform cell that is often terminally inflated, 22-39 × 5-9 Μm, occupying the whole gill edge, optically empty, mixed with small gloeocystidia.

Pileipellis

Orthochromatic in cresyl blue, poorly delimited from the underlying trama, one-layered to obscurely two-layered, forming a very dense tissue up to 200 Μm thick of closely packed hyphae (but easily dissolving in KOH); the lower hyphae intertwined-intricate, gradually more to very irregularly inflated, strongly branching, emitting densely packed, vertical to ascending hyphal extremities; these c. 4 Μm wide, thin-walled, irregularly undulate-twisted, composed of 2-3 subcylindrical cells with the second or third cell often branching and giving rise to two or more terminal cells; these even more irregularly undulate or wavy in outline, not exceeding 60 Μm long, often distinctly inflated near the apex. Subpellis composed of cylindrical, distinctly zebroid encrusted hyphae. Pileocystidia quite common to abundant below the pileipellis, but apparently absent from the pileus surface; immerged, subcylindrical, thin-walled gloeocystidia are very apparent immediately below the subpellis because of their poor, yet very visible contents in the form of dispersed, refringent masses of variable size and because of their relatively important size compared to the surrounding hyphae and other elements, continuing but less abundant in trama underneath.

Clamp connections

Absent in all tissues.

NOTES

This apparently very rare species – we have only seen it once in more than twenty years of fungal exploration in Africa and Madagascar – has been placed by a recently published multigene phylogeny of Russula ( Buyck et al. 2018) in R. subgenus Malodora Buyck & V. Hofst., where it occupies a more or less isolated position, belonging neither to section Pseudocompactae Buyck & V. Hofst. nor to section Edules Buyck & V. Hofst. (see Das et al. 2017).

Both in the field and under the microscope, it reminds rather of some species formerly placed in R. subg. Archaea Buyck &V. Hofst. , in particular the North American R. fattoensis Buyck , because of the very similar structure and composition of the pileipellis. It differs nevertheless from all species placed in subg. Archaea in its much larger spores.

Figures

FIG. 16. — Russula capillaris Buyck, sp. nov. (holotype), morphology of fresh basidioma: A, detail of pileus and stipe surface; B, section showing stipe interior; C, details of gills. Photos: B. Buyck.

FIG. 17. — Russula capillaris Buyck, sp. nov. (holotype), microscopic features of pileipellis: A, pileocystidia near the trama-subpellis transition with schematic contents in one and indication of refringent conglomerates in both other cells; B, detail of zebroid incrustations observed on most subpellis and context hyphae; C, hyphal extremities of the pileus surface. Scale bar: 10 µm. Drawings: B. Buyck.

FIG. 18. — Russula capillaris Buyck, sp. nov. (holotype), microscopic features of the hymenophore: A, spores; B, basidia and basidiola; C, marginal cells of the gill edge; D, gloeocystidia on gill sides; E, gloeocystidia on gill edge. Cystidial contents are mostly schematic, note also the presence of incrusting material that is easily observed near the base of many pleurogloeocystidia. Scale bar: 10 µm, but only 5 µm for spores. Drawings: B. Buyck.