Russula darjeelingensis S. Paloi, K. Acharya & K. Das, 2018

Paloi, Soumitra, Das, Kanad & Acharya, Krishnendu, 2018, Russula darjeelingensis, a new species from Eastern Himalaya, India, Phytotaxa 358 (1), pp. 83-90 : 84-88

Russula darjeelingensis S. Paloi, K. Acharya & K. Das sp. nov., Figures 2 & 3

MycoBank No: MB 823431

Etymology: — To recognise Darjeeling in the state West Bengal ( India), the type locality.

Diagnosis: — Distinct from all the sequenced species of Russula by the nrITS sequence data and all the known species by the combination of morphological features e.g. small sized, white colour pileus with tall and narrow stipe (35–90 × 3–6.5 mm), absence of lamellulae, white spore print and occurrence under Quercus ( Fagaceae ).

Type: — INDIA. West Bengal: Darjeeling district, near Love Road, 27°05′14″N, 88°26′35″S, elev. 2084 m above sea level, 26 July 2016, S. Paloi, CAL 1609 (holotype).

Description: —Pileus 10–46 mm in diam., convex to broadly convex when young, becoming planoconvex to applanate at maturity; surface smooth, moist to semi-moist white (1A1), unchanging when bruised, turning light yellow with KOH, light orange to reddish orange with SV but negative with guaiacol and phenol; margin somewhat translucent; context <1 mm thick, white (1A1), unchanged after exposed in air. L amellae adnate, 3–4 mm broad, white (1A1), unchanging when bruised, turning light orange with SV and brownish red with guaiacol, negative with phenol, regular; edge even, concolorous; lamellulae absent. Stipe 35–90 × 3–6.5 mm, central, smooth, moist to semi moist, more or less equal, white (1A1) in colour, unchanging when bruised, turning light yellow to yellow with KOH, orange to light orange with SV, negative with guaiacol and phenol; context with large cavity, white (1A1), unchanging when bruised; white (1A1), with mycelial pad at the base. Taste mild. Odour indistinct. Spore print white (1A1).

Basidiospores (5.7–)6.5– 7.3 –7.9(–9.0) × (5.3–)6.0– 6.7 –7.2(–8.0) μm, Q=1.05– 1.09 –1.16, globose to sub-globose, ornamentation amyloid, composed of short (0.3–0.6 μm) to high (0.9–1.4 μm) conical warts, free, very rarely few connected, apex obtuse, never reticulate; suprahilar spot amyloid. Basidium (21.5–)27.0–33.6–37.5(–45.0) × (8.0–)9.0– 10.1–11.5(–12.5) μm, clavate to sub-clavate, thin-walled. Lamellae trama 11–20 μm thick, pseudoparanchymatous. Lamellae edge sterile. Hymenial cystidia 39.5–50.0 × 7.2–14.0 μm, clavate to sub-clavate with lageniform to short appendiculate apex, thin-walled, hyaline; content dense, granular, oil granule present with KOH near gill edge; near gill side ca. 48.5–68.0 × 10.5–17.0 μm, same as gill edge. Pileipellis orthocromatic in cresyl blue, distinctly 2– layered, underlying cortex composed of sphearocytes; subpellis ca. 35.0–68.0 μm deep, non-gelatinized, composed of loosely arranged, erect to sub-erect hyphae, ca. 3.5–5.3 μm wide, thin-walled, hyaline, branched, septate hyphal end obtuse; suprapellis 64.5–89.5 μm deep, composed of hyphal elements and cystidia; hyphal elements composed of chains of 4–8 cells of different dimensions, sub-terminal cells 8–14 × 4–11 μm, mostly somewhat inflated, rarely sub-cylindrical, terminal cells 9–18 × 3.5–6 μm, cylindrical to sub-fusoid or sub-obtuse, non-gelatinized, thin-walled, hyaline, branched, septate; pileocystidia 4.5–7.2 μm broad, cylindrical, septate, encrusted, present toward cap centre, thin-walled, hyaline, dense with cytoplasmic contains. Stipitipellis composed of erect to sub-erect hyphae and cystidia; hyphae 2.7–3.6 μm broad, non-gelatinized, thin-walled, hyaline, branched, septate, oil granule present with KOH, hyphal end obtuse; caulocystidia 5.0–7.5 μm broad, cylindrical with short appendiculate apex, thin-walled, hyaline.

Habit and Habitat: — Solitary, scattered, under the Quercus sp. in Quercus and Castanopsis dominated mixed broadleaf forest.

Others specimen examined: — INDIA. West Bengal: Darjeeling district, near VVI, 27°05′20″N, 88°26′05″S, elev. 2086 m above sea level, 12 July 2017, S. Paloi, CUH AM535.

Molecular phylogeny:— The newly generated sequence products were 618 and 646 nucleotides long. All sequences were aligned and the ends trimmed to create a dataset of 765 nucleotides. The phylogenetic relationships of Russula darjeelingensis was inferred from ML analyses ( Fig. 1 ). The tree generated using ML and Bayesian analyses (BA) were identical in topology. Maximum likelihood (ML) analysis recovered a single tree with likelihood values of - InL = 8290.564723. Bayesian analyses reached a standard deviation of split frequencies of 0.004 after 106 generations and the initial 25% trees recovered were excluded as the burn-in. Fig. 1 highlights branch support value recovered by ML and posterior probabilities (PP) majority conscious tree (MLBS: ≥ 50%, PP: ≥ 0.50)

The phylogenetic tree ( Fig. 1 ) revealed that the clade 1 (PP=1.00 and MLBS=100%) represent the members of the Russula subg. Russula and subg. Incrustatula , which are always showed paraphyletic in nature (very recently they are proposed to be merged in a single subgenus with multigene phylogeny as given in Buyck et al. 2018). The two collections of the newly described R. darjeelingensis are monophyletic (marked with bold) and sister to the European R. velenovskyi Melzer & Zvára with moderate support (MLBS = 72% and PP = 0.82). These two species are further sister with R. integriformis Sarnari (the type species of R. subsect. Paraintegrinae) with strong support (MLBS = 96% and PP = 1.00). To maintain the morphology of this subsection should be included R. darjeelingensis ( Sarnari 1998) .

Figures

FIGURE 1. Maximum likelihood tree generated using a HYK+G model of nucleotide evolution. Maximum likelihood bootstrap values> 50% (left of /) and Bayesian posterior probabilities> 0.50 (to the right). The scale bar represents the number of expected changes per site. Lactarius torminosus, L. indigo, L. subindigo and L. deliciosus were selected as outgroup taxa for rooting purpose. Russula darjeelingensis is placed in bold font to highlight its phylogenetic position in the tree. Categorizations of Russula species within the tree follows the classification of Hongsanan et al. (2015) and Sarnari (1998).

FIGURE 2. Russula darjeelingensis (CAL 1609, holotype). A–B. Fresh basidiomata in the field; C. Scanning Electron Micrograph of basidiospore; D. Elements of pileipellis. Scale Bars: A–B = 10 mm, C = 2 μm and D = 10 μm.

FIGURE 3. Macro-microscopic features of Russula darjeelingensis (CAL 1609, holotype). A. Basidiocarp; B. Basidium; C. Hymenial cystidia; D. Pileipellis hyphae and encrusted pileocystidia; E. Caulocystidia; F. Basidiospores. Scale Bars: A = 10 mm, B–E = 10 μm and F = 5 μm (Drawing by S. Paloi).