Lactifluus tropicalis A. Ghosh, I. Bera, D. Chakr. & Hembrom, 2022

Ghosh, Aniket, Bera, Ishika, Chakraborty, Dyutiparna, Hembrom, Manoj E., Verbeken, Annemieke & Das, Kanad, 2022, A new edible species of Lactifluus (Russulaceae) from Shorea robusta dominated forests in tropical India, Phytotaxa 564 (3), pp. 277-287 : 284-285

Lactifluus tropicalis A. Ghosh, I. Bera, D. Chakr. & Hembrom sp. nov. Figs. 2 & 3

MycoBank: MB 843967

GenBank: ON 202982 (nrITS, holotype) , ON 202996 (nrITS) ; ON 202995 (nrLSU, holotype) , ON 202997 (nrLSU) ; ON 007343 (rpb2, holotype) , ON 212013 (rpb2) .

Etymology:— Tropicalis (Lat.) refers to the tropical distribution of the taxon.

Diagnosis:— Lactifluus tropicalis is mainly separated from the closely related L. leoninus on the basis of its nonsulcate pileus margin, mild taste, unchanging latex on exposure, ixocutis to ixotrichoderm pileipellis, habitat and multigene molecular data.

Holotype:— INDIA. West Bengal: Jhargram district, Jhargram city, N 22°25’01.2’’ E 87°00’13.4’’, Alt. 102 m, 12 th August 2021, A. Ghosh & D. Chakraborty, AGDC _21-05 ( CAL 1873 , holotype!).

Description:— Pileus 25–100 mm diam., hemispheric to convex when young, gradually planoconvex to applanate with a broad shallow to deep depressed centre, becoming infundibuliform with maturity; surface dry, viscid when wet, smooth, velvety, sometimes finely wrinkled near the centre, light yellow to pastel yellow (3A4) when young gradually becoming butter- to straw-colour or yellowish white to, pale yellow (3–4A2–3) with maturity; margin entire, decurved to uplifted with age, often cracked at maturity. Lamellae up to 8 mm deep, decurrent, distant (4–5/ 10 mm at pileus margin), moderately thick, brittle, forked near the middle and margin; lamellulae in up to 5 series, yellowish white (2– 4A2); edge entire, smooth, concolorous. Stipe 27–40 × 7–20 mm, central, short, broadly clavate to cylindrical; surface dry, chalky white (1–2A1) with grayish yellow (4B3–4) spots, unchanging after bruising. Context thick in pileus and stipe, yellowish white (1–2A2), unchanging after bruising; turning deep to dark turquoise (24E–F7–8) in guaiacol and salmon pink (6A4) in FeSO 4 respectively. Taste mild. Latex watery to transparent, unchanging upon exposure. Odor pleasant. Spore print not recorded.

Basidiospores (6.5–)6.9– 8.0 –9.2 × (6.0–)5.9– 6.8 –7.7(–8.0) μm, [n = 30, Q = 1.04– 1.17 –1.30(–1.31)], subglobose, broadly ellipsoid to ellipsoid; ornamentation amyloid, up to 0.6 μm high, composed of subconical, conical to sometimes elongated warts mostly connected by fine lines; suprahilar plage inamyloid. Basidia 42–57 × 9–11 µm, subclavate, 4-spored; sterigmata up to 9 µm long. Pleuromacrocystidia absent. Pleuropseudocystidia abundant, up to 35 µm emergent, 7.5–12 µm broad, subcylindrical to subclavate with capitate, moniliform, appendiculate or obtuse-rounded apices, thin-walled; content dense, heteromorphous, granular to crystalline. Lamellae edge sterile. Cheilocystidia not found. Subhymenium up to 37 µm thick, cellular, made up of pseudoparenchymatous cells. Hymenophoral trama composed of few nests of sphaerocytes connected with hyphae and intermixed with lactiferous hyphae. Pileipellis up to 150 µm thick, a transition between ixocutis to ixotrichoderm composed of interwoven, multiseptate, repent to uprising hyphae; terminal cells 45–100 × 2.0–4.5 μm, mostly cylindrical or subcylindrical with obtuse-rounded apex, thin-walled. Stipitipellis an ixocutis, up to 53 µm thick, composed of interwoven, multiseptate, rarely branched hyphae. Clamp connections absent in all tissues.

Habitat:—Solitary to scattered, growing in ectomycorrhizal association with Shorea robusta in tropical deciduous forests.

Additional specimens examined:— INDIA. West Bengal: Jhargram district, Lodhasuli, N 22°19’50’’ E 87°01’41’’, Alt. 80 m, 12 August 2020, I. Bera , IB 20-08 ; Jhargram district , Jhargram city, N 22°25’01.2’’ E 87°00’13.4’’, Alt. 102 m, 14August 2020, I. Bera, IB 20-053 ; Jharkhand: Rajmahal hills, Sahibganj district, Borio block, Pir-Baba Kairasol forest area, N 25°09’41.7’’ E 87°40’31.9’’, Alt. 125 m, 24 August 2021, M. E. Hembrom, MEH-21-09; Rajmahal hills, Pakur district , Hiranpur block, Talpahari to Tugutola forest area, N 24°37’02.6’’ E 87°40’45.2’’, Alt. 94 m, 26August 2021, A. Ghosh, AG 21-15 (JH) .

Figures

FIGURE 2. Lactifluus tropicalis (CAL 1873, holotype). a–c. Fresh and dissected basidiomata in the field and basecamp, d. Transverse section through pileipellis showing elements, e. Transverse section through lamellae showing basidia, f–j. Transverse section through lamellae showing pleuropseudocystidia, k & l. SEM micrograph of basidiospores. Scale bars: d= 20 μm, e−j= 10 μm, k & l= 2 μm.

FIGURE 3. Lactifluus tropicalis (CAL 1873, holotype). a. Pleuropseudocystidia, b. Basidiospores, c. Basidia, d. Pileipellis. Scale bars: a, c, d= 10 µm, b= 2 µm.