Russula benghalensis S. Paloi & K. Acharya, sp. nov.

Index Fungorum number: IF 831253; MycoBank number: MB 831253; Facesoffungi Number: FoF 06141; Figs. 108, 109

Etymology: ‘benghalensis’ refers to the type locality West Bengal.

Holotype: CUH AM654.

Basidiocarp small to medium. Pileus 14‒35 mm diam, convex to broadly convex at early stage, becoming broadly convex to applanate, or sometime upturned with a central depression, surface smooth when young, becoming cracked or areolate, moist to semi-moist, gelatinized, brownish orange (7C5‒6), light brown (7D6) to reddish brown (8D5) at center, towards margin greyish orange (5B6; 6B3), brownish orange (6C4‒5) or greyish red (7B4), no change after bruising, turns orange-red with KOH, orange-pink with SV, light pink to pink with phenol and guaiacol; context very thin (<1 mm), white (1A1) to cream, no change when exposed to air. Lamellae ca. 2‒3 mm broad, adnate, regular, white (1A1), turns brown-orange to brick red with guaiacol and phenol, negative with SV; margins even, concolorous; lamellulae 1‒2 tiers. Stipe central, 20‒40×3‒6 mm, slightly curved, more or less equal, semi moist, ruinose; greyish orange (5B3) to pale orange (6A3) or light orange (6A4), no change on bruising, turning yellow with KOH, negative reaction to phenol and guaiacol; context chambered, white (1A1), no change when exposed to air. Odour unknown. Taste mild. Spore print white (1A1) to cream. Basidiospores (5.5‒)6.3‒7.5(‒8.0)×(4.6‒)5.0‒6.5(‒7.5) µm, L=6.7, W=5.8, Q=1.07‒1.25, subglobose to broadly ellipsoid, ornamentation amyloid, composed of short (0.3‒0.4 µm) to high (0.6‒0.8 µm) isolated individual warts, obtuse to sometime lobed apex, never reticulated. Basidium 35.5‒61.0×5.5‒11.5 µm, clavate to subclavate, hyaline, thin-walled. Lamellar trama pseudoparanchymatus. Lamellae edge sterile. Hymenial cystidia 30.5‒68.5×6.0‒12.5 µm, sub-clavate to sub-cylindrical with moniliform to appendiculate apex, oil granules present in KOH near gill edge; pleurocystidia: two types of cystidia present, one same as gill edge, another 53‒70 × 9.0‒14.0 µm, clavate to subclavate with round or obtuse apex, thin-walled, hyaline, oil granule present when viewed with KOH. Pileipellis a trichoderm, orthocromatic in Cresyl Blue, distinctly three layers, underlining cortex composed of spherocytes; subpileus 50‒85 µm deep, composed of tightly arranged hyphal cells, 3.5‒5.5 µm broad, thin-walled, hyaline, end obtuse, oil granules present when mounted in KOH; suprapellis 30‒65 µm deep, non-gelatinous, composed of erect to suberect hyphae, 3.0‒5.0 µm broad, thin-walled, hyaline, end obtuse or round; oleiferous hyphae 3.5‒7.0 µm broad, abundant towards cap  centre, thin-walled; pileocystidia 27.0‒40.0×5.0‒7.0 µm, scattered at margin, cylindrical to subcylindrical with less pointed apex or sometimes rounded, thin-walled, hyaline, oil granules present when mounted in KOH. Stipitipellis composed of erect to suberect hyphae, 4.0‒6.0 µm broad, non-gelatinous, thin-walled, hyaline, end obtuse; caulocystidia 43.0‒69.0×5.0‒7.0 µm, cylindrical with moniliform to pointed apex, thin-walled, hyaline, oil granules present when viewed with KOH. Clamp-connections absent in all tissues.

Habit and habitat: solitary, scattered, grows under Shorea robusta tree.

Material examined: INDIA, West Bengal, Nadia district, near Bethuradhari forest, 23°35′52.2492′′ N, 88°23′34.0944′′ E (elev. 25 m), 20 August 2016, S. Paloi and A. K. Dutta, CUH AM654 (holotype); Nadia district, near Bethuradhari forest, 23°35′52.1088″ N, 88°23′33.8424″ E (elev. 27 m), 5 August 2017, S. Paloi and K. Acharya, CUH AM655.

GenBank numbers: ITS: MK414583, MK414584; LSU: MK496844.

Notes: Russula benghalensis is easily recognized by the presence of a small-sized pileus, which turned orange-red with KOH, adnate lamellae with one to two lamellulae, a mild taste, basidiospores with ornamentation composed of isolated warts, a trichodermal type of pileipellis, the presence of oleiferous hyphae and pileocystidia.

Fig. 108 Russula benghalensis (CUH AM654, holotype). a Fresh basidiocarps. b SEM photograph of basidiospores. Scale bars: a=10 mm, b=2 µm

Fig. 109 Morphological features of Russula benghalensis (CUH AM654, holotype). a Basidia. b Cystidia near gill edge. c Cystidia near gill side. d Pileipellis. e Oleiferous hyphae. f Pileocystidia. g Basidiospores. Scales bars: a=10 mm, b–g=10 µm, h=5 µm