Rhodocollybia variabilicolor Antonín, R. Ryoo & Ka, 2024

Ryoo, Rhim, Ka, Kang-Hyeon & Antonín, Vladimír, 2024, The genus Rhodocollybia (Omphalotaceae, Basidiomycota) in the Republic of Korea, Phytotaxa 642 (2), pp. 111-126 : 120-121

Rhodocollybia variabilicolor Antonín, R. Ryoo & Ka , sp. nov. Figs. 3D‒G , 6A‒C

Mycobank MB 852257

Etymology:— variabilicolor refers to the high variability of the pileus colour.

Diagnosis:—It differs from R. butyraceoides by usually larger basidiomata, darker coloured pileus, different Qvalue of basidiospores, the presence of regular, irregular, branched to coralloid pileipellis terminal cells, and different ITS sequences.

Holotype:— REPUBLIC OF KOREA. Jeollabuk-do, Jinan-gun, Unjangsan Natural Recreation Forest, 31 August 2016, V. Antonín 16.138, K.- H. Ka & K. S. Kim ( BRNM 840491 ).

Description:— Pileus 15‒60 mm broad, almost hemispherical, conical-convex, broadly convex, broadly conical with obtuse central umbo when young, then plano-convex to applanate with or without low obtuse central umbo when mature, margin involute then straight, sometimes slightly undulate, slightly radially innately fibrillose or glabrous when young, glabrous when old, smooth, hygrophanous, mostly at margin or up to one half of the diameter, translucently striate, sometimes slippery when young, light brown to brown (6D4‒5, 7D‒E6‒7, 7F8), greyish orange (5A‒B3), pale brown or yellowish ochraceous at centre, brownish, pale brown, pale ochraceous, beige or pale greyish brownish towards margin, sometimes concentrically zonate. Lamellae moderately close, L = approx. 32‒50, l = (2‒) 3‒5, emarginate and almost free, attached with tooth or slightly decurrent with tooth, white, then yellowish white (± 3‒4A2), with concolorous, denticulate edge. Stipe 40‒80 (‒100) × 3‒7 mm, cylindrical, with clavate to irregularly bulbose base (10‒15 mm wide), sometimes laterally compressed, fibrillose-flocculose becoming pruinose at apex, smooth or finely longitudinally fibrillose, pale (greyish) brownish, (dirty) whitish with brownish tinge; basal mycelium white, sometimes ascending up to one quarter or one third of the stipe length. Context white or pale brownish in pileus, whitish and hollow in stipe, with fungoid smell and mild taste.

Basidiospores (5.5‒) 6.0‒8.5 (‒9.0) × 3.0‒4.5 µm, average 7.08 × 3.67 µm, E = 1.57‒2.28 (‒2.45), Q = 1.82, ellipsoid to ellipsoid-fusoid, sublacrymoid, both thin-walled and non-dextrinoid, and slightly thick-walled and dextrinoid spores present, mostly in tetrads. Basidia 24‒32 × 6.0‒9.0 µm, 4-spored, clavate; crassobasidia sometimes present. Basidioles 12‒33 × 2.5‒8.0 µm, clavate, cylindrical, subfusoid. Cheilocystidia 21‒50 (‒68) × (3.0‒) 4.0‒11 (‒17) µm, subcylindrical, clavate, fusoid, subfusoid, sometimes rostrate, mostly irregular, branched to coralloid, thin-walled. Trama hyphae cylindrical or subinflated, thin-walled, colourless, smooth, non-dextrinoid, 3.0‒20 µm wide. Pileipellis an ixocutis composed of radially arranged, cylindrical, thin-walled, smooth or minutely incrusted, 3.0‒10 µm wide hyphae; terminal cells adpressed or erect, cylindrical, fusoid, narrowly clavate, obtuse, thin-walled, regular, irregular, branched or coralloid, 2.0‒8.0 µm wide. Stipitipellis a cutis of cylindrical, thin- to slightly thick-walled, ± colourless, smooth or minutely incrusted, non-dextrinoid, 3.0‒6.0 µm wide hyphae arranged in parallel. Caulocystidia (terminal cells) 25‒82 × 3.0‒8.0 µm, adpressed to suberect, erect, cylindrical, subfusoid, subclavate, obtuse. Clamp connections present in all tissues.

Ecology:—On soil, in litter of Acer palmatum , Castanea crenata , Fraxinus sp. , Keria sp. , Larix sp. , Pinus densiflora , Quercus acutissima and Quercus sp.

Other specimens examined:— REPUBLIC OF KOREA. Seoul, Hongneung Arboretum , 13 July 2009, V. Antonín 09.92 & R. Ryoo ( BRNM 718751 ) ; Chungcheongnam-do, Tean Peninsula, Anmyeondo Natural Recreation Forest , 11 July 2014, V. Antonín 14.82 & K.- H. Ka ( BRNM 840482 ) ; Chungcheongnam-do, Tean Peninsula, Seosan, Gaesimsa Temple , 15 July 2014, V. Antonín 14.89 & K.- H. Ka ( BRNM 840483 ) ; Chungcheongnam-do, Tean Peninsula, Seosan, Yonghyeon National Natural Recreation Forest , 15 July 2014, V. Antonín 14.93 & K.- H. Ka ( BRNM 840484 ) ; Chungcheongbuk-do, Chungju, Mt. Sim Hang , 24 August 2015, V. Antonín 15.85, K.- H. Ka, K. S. Kim & J. A. Kang ( BRNM 840486 ) ; Chungcheongbuk-do, Youngdong-gun, Sangchon-myeon, Mulan Valley , 25 August 2015, V. Antonín 15.86, K.- H. Ka, K. S. Kim & J. A. Kang ( BRNM 840487 ) ; Kangwon-do, Hongcheon, Bukbang-myeon , Seongdongri , 27 July 2007, V. Antonín 07.151 ( BRNM 715004 ) ; Chungcheongbuk-do, Chungju, Bonghwang Natural Forest , 29 August 2015, V. Antonín 15.126, K.- H. Ka, K. S. Kim & J. A. Kang ( BRNM 840488 ) .

Remarks:— Rhodocollybia variabilicolor is characterized by a pileus hygrophanous, mostly translucently striate, light brown to brown, greyish orange, pale brown or yellowish ochraceous and a stipe basally clavate to bulbose, pale (greyish) brownish, (dirty) whitish and brownish tinged. Basidiospores are rather large, (5.5‒) 6.0‒8.5 (‒9.0) × 3.0‒4.5 µm and cheilocystidia 21‒50 (‒68) × (3.0‒) 4.0‒11 (‒17) µm large, variable in shape, mostly irregular, branched to coralloid.

Rhodocollybia variabilicolor is a macro- and microscopically rather variable species also very close to R.butyracea , R. butyraceoides and R. asema and macro- and micromorphologically extremely difficult to distinguish from these taxa. Rhodocollybia butyraceoides differs by usually smaller basidiomata (pileus 10‒45 mm broad, stipe 25‒65 × 1.5‒6 mm), different Q-value of basidiospores (2.04 vs. 1.82 for R. variabilicolor ) and the absence of (sometimes) branched to coralloid pileipellis terminal cells. Rhodocollybia butyracea and R. asema differ only by a paler coloured pileus, slightly narrower basidiospores (Q-value 1.82 vs. 2.1 for both R. butyracea and R. asema ) and shorter, 15‒35 µm long, cheilocystidia ( Antonín & Noordeloos 2010). The differences of R. variabilicolor from the similar taxa discussed above for R. butyraceoides are the same differences also for R. variabilicolor .

Figures

FIGURE 3. BasidiomataA. Rhodocollybia maculata (BRNM 840489).B. R. butyraceoides (BRNM 840485).C. R. butyraceoides (BRNM 840490, holotype). D. R. variabilicolor (BRNM 718751). E. R. variabilicolor (BRNM 840482). F. R. variabilicolor (BRNM 840488). G. R. variabilicolor (BRNM 840491, holotype). H. R. hongneungensis (BRNM 718721, holotype). Photos by: V. Antonín.

FIGURE 6. Rhodocollybia variabilicolor (BRNM 840488). A. Cheilocystidia. B. Basidiospores. C. Pileipellis. Scale bar = 20 µm. Drawings by V. Antonín and R. Ryoo.