Russula boddingii Hembrom, D. Chakr., A. Ghosh & K. Das
MycoBank number: MB; Index Fungorum number: IF; Facesoffungi number: FoF 11436;
Pileus medium to large-sized, 30–160 mm in diam., convex at young, becoming planoconvex to applanate, centrally depressed to umbilicate, sometimes uplifted at maturity, margin smooth, entire when young becoming decurved to plane, uplifted with age; cuticle smooth, viscid and shiny when wet, dull upon drying, peeling to 1/4th of the radius, greyish white (1B2) to grey (2–5B2) with yellowish white (3A2) tinges. Pileus context up to 9 mm thick at the disc becoming narrower towards margin, compact, brittle, firm, chalky white (1–2A1), changing first orange red (8A8) or brownish red (8C6–7), then blackish when cut or bruised; turning dull green (27D3–4) with of FeSO4, and deep to dark turquoise (24E–F7–8) in guaiacol. Lamellae unequal, of different lengths, narrow, up to 5 mm deep, sub-decurrent to decurrent, crowded (15–22/cm at pileus margin), chalky white (1–2A1) to yellowish white (3A2), forked at different distances from the stipe; edges entire and concolorous. Stipe 25–57 × 9–23 mm, cylindrical, subclavate to clavate, central, firm and fleshy; surface dry, smooth, chalky white (1–2A1) to greyish white (1B2); turning dull green (27D3–4) with of FeSO4 and deep to dark turquoise (24E–F7–8) in guaiacol. Stipe context solid, chalky white (1–2A1), changing first orange red (8A8) or brownish red (8C6–7), then blackish when cut or bruised; turning dull green (27D3–4) with FeSO4 and deep to dark turquoise (24E–F7–8) in guaiacol. Odour insignificant. Taste mild. Spore print not obtained, but most likely white.
Basidiospores globose, subglobose to broadly ellipsoid, (5.8–)6.2–6.7–7.2(–7.8) × (5.5–)5.6–6.0–6.5(–7) μm, Q=(1–)1.07–1.12–1.16(–1.20); ornamentation composed of relatively dense, obtuse-rounded conical amyloid warts (up to 0.8 µm high), connected by thick ridges forming reticulation; suprahilar spot inamyloid; apiculi up to 1.2 μm long. Basidia (28–)34.5–40–45(–48) × 8–9–10(–11) µm, 4-spored, narrowly clavate to clavate, sterigmata up to 8 µm long; basidiola cylindrical to clavate. Hymenial gloeocystidia on the lamellae sides (22–)33.5–54.5–75.5(–112) × (4–)5–7.5–9.5(–10) µm, emergent up to 14 μm above the other elements of the hymenium, usually smaller and narrower near the lamellae edges 31–43–55(–65) × 3–5–6(–7) µm, cylindrical to clavate with capitate to moniliform apex; contents completely or partly filled with brown refractive bodies, not reacting in sulfovanillin. Marginal cells absent. Subhymenium layer up to 20 µm thick, pseudoparenchymatous. Hymenophoral trama mainly composed of large nests of sphaerocytes and intermixed with hyphal elements. Pileipellis orthochromatic in Cresyl Blue, sharply delimited from the underlying context, 300–380 μm thick, two-layered; suprapellis 140–200 μm thick, composed of narrow, ascending hyphal terminations; subpellis 160–180 μm deep, composed of more or less dense, horizontally oriented hyphae. Acid-resistant incrustations absent. Hyphal terminations near the pileus margin long, flexuous, with multiple septa, scarcely branched at the bases, sometimes with lateral branches, thin-walled, partly filled with irregular refractive bodies containing brown pigments; terminal cells (39–)44–58–72(–90) × (3–)4–4.5–5.5(–6) µm, narrowly cylindrical to subulate, apically obtuse-rounded or acute; subterminal cells and the cells below often gradually wider, usually shorter. Hyphal terminations near the pileus centre apically more attenuated; the terminal cells slightly shorter and less wide, measuring (26–)34.5–50–65(–85) × (2–)3–3.5–4.5(–5) µm. Pileocystidia absent. Clamp connections absent from all tissues.
Material examined: India, West Bengal, Jhargram district, Lalgarh Karamsol, alt. 73 m, N 22º34’12.9″ E 87º05’25.2″, 1 July 2018, M.E. Hembrom, MEH-18-01 (CAL 1860, holotype!).
Sequence data: ITS: OL469097 (nrITS Holotype) and OL469118 (nrITS) LSU: ON365924 (nrLSU, holotype) and ON365926 (nrLSU) mtSSU: ON387513 (mtSSU, holotype) and ON387510 (mtSSU) rpb2: ON418909 (rpb2, holotype) and ON418910 (rpb2)
Notes: In its most recent interpretation, R. subg. Compactae (Fr.) Bon, emend. Buyck & V. Hofst. (in Hongsanan et al. 2015) includes species that produce more or less thick-fleshed, very small to large basidiomata with dull to dingy white, brown, grey to black pileus, regularly unequal, polydymous lamellae, a mild to very acrid context that is reddening, greying, blackening, rarely browning and often with unpleasant smell, white spore print and spores with inamyloid suprahilar spot; gloeocystidia mostly capitate with one central knob or more frequently with two excentrical knobs. In a recent multicolus phylogeny (Buyck et al. 2018), this subgenus was shown to be composed of two highly supported lineages: sect. Polyphyllae Buyck & V. Hofst. and sect. Nigricantinae Bataille, which is the core group of this subgenus as it holds the European R. nigricans, the type species. With very few exceptions, species of section Nigricantinae have basidiomata that react most frequently by first reddening on bruising before turning to black. This feature, in combination with the unequal, polydymous gills, is still considered to constitute the easiest field character to recognize species of this section (Das et al. 2020).
A nBLAST of the obtained ITS sequences of our specimens undeniably placed our new species in sect. Nigricantinae with sequences MN075499 (99.51% similarity), MN580113 (99.05% similarity) and JN969389 (99.13% similarity), all three obtained from deciduous dipterocarp forests in Thailand (Pachit et al. 2020, Poshri et al. 2012, Yuwa-amornpitak & Yeunyaw 2020), representing earlier reports of R. boddingii. None of the other sequences from nBLAST results was more similar than 96% to our species, and all suggested a placement of our new species in the R. densifolia lineage.
In recent years, several new Asian species have been published in sect. Nigricantinae (Zhou et al. 2020, Das et al. 2020), but none of these had crowded gills as in the R. densifolia lineage. The latter lineage has been retrieved as a highly supported clade in recent multigene phylogenetic analyses (Buyck et al. 2018, De Lange et al. 2021). So far, only five described species have been shown to be part of this lineage: the European R. densifolia, R. densissima, R. atramentosa and R. fuliginosa, as well as the Australian R. ingwa. Our phylogeny now shows that at least five additional Asian species in this lineage await description. Vidal et al. (2019) proposed an enlarged concept of Laricinae based on their multilocus phylogenetic analysis, including in this subsection one or two additional clades of species occupying a very different habitat as they associate with deciduous trees in the lowland Mediterranean area. Given the ecological differences between Laricinae and these lineages, we think such a wide concept for a subsection needs confirmation. Nevertheless, they demonstrated the abundant occurrence of semi- to fully hypogeous taxa in this larger clade as already suggested by Whitbeck (2003).
Figures 1. Russula boddingii (CAL 1860, Holotype) a–d Fresh and dissected basidiomata in the field and basecamp. e, f Transverse section through pileipellis showing elements. g Transverse section through lamellae showing hymenial gloeocystidia near the lamellae edges. h, i Transverse section through lamellae showing hymenial gloeocystidia near the lamellae sides. j Transverse section through lamellae showing basidia. Scale bars: e = 100 μm, f−j = 10 μm.