Rhodocollybia butyraceoides 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 : 118-119

Rhodocollybia butyraceoides Antonín, R. Ryoo & Ka , sp. nov. Figs. 3B, C , 5A‒C

Mycobank MB 852256

Etymology:— butyraceoides refers to the similarity to R. butyracea .

Diagnosis:—It differs from R. butyracea by slightly smaller basidiomata, paler stipe, larger cheilocystidia and different ITS sequences.

Holotype:— REPUBLIC OF KOREA. Jeollabuk-do, Jinan-gun, Unjangsan Natural Recreation Forest, 7 September 2016, V. Antonín 16.168 & R. Ryoo ( BRNM 840490 ).

Description:— Pileus 10‒45 mm broad, convex with obtuse centre and involute margin when young, then plano-convex to applanate with plane centre or with less distinct to distinct obtuse central umbo, margin straight or uplifted, hygrophanous, smooth, glabrous, slightly translucently striate at margin, sticky and slippery when moist, brownish orange to brown (6B‒C4‒5, 7D‒E7) or brownish grey to reddish brown (± 6C‒D2, 8D‒E4) when young, pale brownish orange (6C6) or brownish grey to reddish brown at centre only, otherwise beige or whitish with brownish or ochraceous tinge when old, margin paler, drying to dirty whitish cream with brown centre. Lamellae close, L = approx. 40‒60, l = 3‒6, emarginate and shortly adnate sometimes with small tooth, slightly ventricose, pale cream, later yellowish cream, with concolorous, finely pubescent edge. Stipe 25‒65 × 1.5‒6 mm, cylindrical, sometimes laterally compressed, sometimes curved at base, clavate towards base (up to 10 mm), finely longitudinally fibrillose, finely pruinose to almost glabrous at apex, milky white with brownish tinge towards base or entirely pale greyish brownish overall; basal tomentum white. Context watery brownish in pileus, watery white in hollow stipe, with fungoid smell and mild to bitterish taste.

Basidiospores (6.0‒) 6.5‒8.0 (‒9.0) × 2.8‒4.0 µm, average 7.30 × 3.62 µm, E = (1.56‒) 1.67‒2.42 (‒2.86), Q = 2.04, ellipsoid to ellipsoid-fusoid, sublacrymoid, both thin-walled and non-dextrinoid, and slightly thick-walled and dextrinoid spores present. Basidia 22‒30 × 7.0‒8.0 µm, 4-spored, clavate. Basidioles 12‒32 × 2.5‒8.0 µm, clavate, cylindrical, subfusoid. Cheilocystidia 21‒50 (‒65) × 4.5‒10 (‒15) µm, variable in shape, subcylindrical, clavate, broadly clavate, subfusoid, fusoid, thin-walled, regular, irregular to subcoralloid. Trama hyphae cylindrical or subinflated, thin-walled, colourless, non-dextrinoid, 3.0‒20 µm wide. Pileipellis an ixocutis composed of radially arranged, cylindrical, thin-walled, smooth or minutely incrusted, sometimes diverticulate, 3.0‒8.0 µm wide hyphae; terminal cells adpressed or erect to suberect, cylindrical, narrowly clavate, sometimes branched, obtuse, thin-walled, regular or irregular. Stipitipellis a cutis of cylindrical, thin- to slightly thick-walled, ± colourless, sometimes minutely incrusted, non-dextrinoid, 3.0‒6.0 (‒7.0) µm wide hyphae arranged in parallel. Caulocystidia (terminal cells) sometimes very rare, adpressed to erect, narrowly clavate, clavate, fusoid to cylindrical, mixed with scattered clavate or cylindrical terminal cells. Clamp connections present in all tissues.

Ecology:—On soil, in litter under Pinus densiflora in a bamboo growth and under Carpinus laxiflora , Castanea crenata , Pinus densiflora , Quercus acutissima , Quercus mongolica and Quercus sp. in mixed forests.

Other specimens examined:— REPUBLIC OF KOREA. Kangwon-do, Pyeongchang, Mt. Taegi , 26 July 2009, V. Antonín 09.153 & R. Ryoo ( BRNM 718810 ) ; Chungcheongnam-do, Tean Peninsula, Mt. Baekhwa , 10 July 2014, V. Antonín 14.76 & K.- H. Ka ( BRNM 840481 ) ; Chungcheongnam-do, Yesan-gun, Mt. Gaya , 16 July 2014, V. Antonín 14.97 & K.- H. Ka ( BRNM 840485 ) .

Remarks:— Rhodocollybia butyraceoides is characterized by a pileus hygrophanous,at margin slightly translucently striate, brownish orange to brown or brownish grey to reddish brown, a stipe clavate towards base, milky white and basally brownish tinged or entirely pale greyish brownish. Basidiospores measure (6.0‒) 6.5‒8.0 (‒9.0) × 2.8‒4.0 µm, and cheilocystidia are variable, 21‒50 (‒65) × 4.5‒10 (‒15) µm large.

Rhodocollybia butyraceoides is very close to R. butyracea and the paler coloured R. asema based on our ITS sequence comparison ( Fig. 1 ) and it is sometimes difficult to distinguish these taxa morphologically. Rhodocollybia asema differs by slightly larger basidiomata (pileus 30‒80 mm broad, stipe 40‒90 × 4‒12 mm), a darker, sepia, grey-brown, red-brown or brown-red stipe, and smaller, 15‒35 × 3.0‒10 µm, often inconspicuous cheilocystidia, which are often (sub)coralloid ( Antonín & Noordeloos 2010, Ludwig 2012).

Among other phylogenetically close taxa to R. butyraceoiodes , R. pandipes Halling & J. L. Mata (in Mata et al. 2004: 346) differs by a brown to reddish brown, cinnamon brown to caramel brown, brownish orange, outward yellow-brown to grey-brown, pale orange, greyish yellow to cream pileus, a larger, 50–120 (‒180) × 4–10 mm, base up to 20 mm broad, buff pinkish, greyish orange, near base pinkish brown, orange-brown, reddish brown to dark red-brown stipe, and slightly smaller, 4.4–9.6 × 2.8–4.8 μm, average 6.4 × 3.6 μm, basidiospores ( Mata et al. 2004); R. ciliatomarginata K.P.D. Latha & Manim. (in Deepna Latha et al. 2018: 159), has smaller basidiomata (pileus 2–29 mm broad, stipe 4–45 × 1–6 mm), a pinkish white pileus, an orange-white or greyish orange stipe, an unpleasant, dried natural rubber latex-like smell, smaller, more distinctly ellipsoid basidiospores, 6–8 × 3–3.5 μm, Q = 2.21 ( Deepna Latha et al. 2018); R. olivaceogrisea J.L. Mata & Ovrebo (in Mata et al. 2016: 240) distinctly differs by a greenish grey, olive brown pileus with greyish hues, remaining dark olive at the umbo, losing greenish colour with age to drab greyish yellow, a drab olive stipe becoming olive brown or greyish buff at base ( Mata et al. 2016); R. purpurata (G. Stev. 1962: 73) J.A. Cooper (2014: 278) is distinct by a nearly black to dark violet pileus when fresh becoming greyish magenta when dry, orange-grey, reddish grey to brownish grey lamellae and a stipe with similar hues to the pileus but paler ( Cooper 2014); R. utrorensis A. Sattar, M. Kiran & Khalid (2018: 271) has a more distinctly dull brown coloured pileus and larger and narrower basidiospores, (6–) 6.2–9.4 (–10.9) × (3.3–) 3.6–4.7 (‒4.8) μm ( Sattar et al. 2018). Among other morphologically similar species, R. tenuipes J.L. Mata, TJ. Baroni & K.W. Hughes (in Mata et al. 2016: 242) has a burnt sienna, dull red-brown, cinnamon brown pileus, a cylindrical, sometimes only slightly basally broadened stipe and smaller cheilocystidia, 20–32 × 4–7 μm ( Mata et al. 2016); R. eucalyptorum ( Cleland 1931: 156) J.A. Cooper (2023: 2) especially differs by distinctly smaller, 5–5.5 × 3.5 µm basidiospores ( Cleland 1931).

Figures

FIGURE 1. Phylogenetic tree for ITS r DNA of the genus Rhodocollybia. New species were indicated in bold.

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 5. Rhodocollybia butyraceoides (BRNM 840481). A. Cheilocystidia. B. Basidiospores. C. Pileipellis. Scale bar = 20 µm. Drawings by V. Antonín and R. Ryoo.