Rhodocollybia hongneungensis Antonín, R. Ryoo & K.H. 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 : 121-123

Rhodocollybia hongneungensis Antonín, R. Ryoo & K.H. Ka , sp. nov. Figs. 3H , 7A‒C

Mycobank MB 852258

Etymology:—The specific epithet refers to the locality of this species.

Diagnosis:—It differs from R. butyraceoides by a usually darker pileus, slightly larger basidiospores (average of length 7.84 µm), rather small, slightly differently shaped cheilocystidia and different ITS sequences.

Holotype:— REPUBLIC OF KOREA. Seoul, Hongneung Arboretum , 11 July 2008, V. Antonín 08.93 & R. Ryoo (BRNM 718721) .

Description:— Pileus 15‒42 mm broad, conico-convex or broadly conical with small obtuse central umbo and slightly inflexed margin when young, then plano-conical to almost applanate, with ± plane centre, and straight to slightly uplifted margin, hygrophanous, not translucently striate or only slightly at outermost margin, except for centre finely fibrillose-tomentose centre, sometimes slightly rugulose at centre when old, dirty ochre brown, greyish beige (± 5‒6B‒C3, 5B4) or greyish orange (6C6) and drying to pale dirty yellowish ochre, pallescent, almost whitish towards margin. Lamellae close, L = approx. 35‒40, l = 3‒4, slightly emarginate and attached with tooth or slightly decurrent with tooth, then broadly adnate to slightly decurrent when old, often intervenose at base, pale yellowish cream then yellow orangish (3‒4A2), with concolorous, serrulate edge. Stipe 35‒70 × 3‒5 mm, cylindrical, slightly clavate at base (up to 9 mm), finely fibrillose-pruinose to flocculose at apex, elsewhere slightly longitudinally fibrillose, watery white, pale yellow (paler than 3A2) or yellow ochre (paler than 4A3); basal mycelium white, ascendant up to one quarter or one half of the stipe length. Context dirty whitish, hollow in stipe, without special smell and with mild taste.

Basidiospores 7.0‒8.5 × 3.5‒4.5 µm, average 7.84 × 3.91 µm, E = (1.67‒) 1.83‒2.07 (‒2.25), Q = 2.02, lacrymoid, ellipsoid to ellipsoid-fusoid, mostly thin-walled and non-dextrinoid and with fewer spores slightly thick-walled and dextrinoid (approx. 10‒20 %). Basidia 22‒31 × 7.0‒9.0 µm, 4-spored, clavate. Basidioles 15‒31 × 3.0‒10 µm, clavate, cylindrical, subfusoid. Cheilocystidia 17‒32 × 4.0‒10 µm, cylindrical, clavate, narrowly fusoid or fusoid, mostly irregular, branched, lobate, thin-walled. Trama hyphae cylindrical, thin-walled, colourless, non-dextrinoid, up to 12 µm wide. Pileipellis an ixocutis composed of radially arranged, cylindrical, thin-walled, smooth, up to 8.0 (‒10) µm wide hyphae; terminal cells adpressed or erect, cylindrical, clavate, obtuse, mostly regular, thin-walled. Stipitipellis a cutis of cylindrical, slightly thick-walled, ± colourless, smooth, non-dextrinoid, up to 5.0 (‒6.0) µm wide hyphae arranged in parallel. Caulocystidia absent; scattered clavate or cylindrical terminal cells present. Clamp connections present in all tissues.

Ecology:—On detritus, under Acer sp. , Castanea crenata , Pinus densiflora and Quercus mongolica .

Other specimen examined:— REPUBLIC OF KOREA. Seoul, Hongneung Arboretum, 11 July 2008, V. Antonín 08.94 & R. Ryoo (BRNM 718722).

Remarks:— Rhodocollybia hongneungensis is characterized by a pileus greyish beige, ochre brown, greyish orange or pale yellow ochraceous, a stipe slightly clavate, watery white, whitish yellowish or yellow ochre. Basidiospores are 7.0‒8.5 × 3.5‒4.5 µm, lacrymoid, ellipsoid to ellipsoid-fusoid and cheilocystidia 17‒32 × 4.0‒10 µm, cylindrical, clavate, (narrowly) fusoid, irregular, branched, lobate.

Rhodocollybia hongneungensis is well characterized phylogenetically and morphologically. Macroscopically R. butyraceoides is a similar taxon. However, R. butyraceoides differs by a usually darker, translucently striate pileus (at least at margin), slightly smaller basidiospores (average 7.30 × 3.62 µm) and rather small, slightly differently shaped cheilocystidia. Rhodocollybia utrorensis A. Sattar, M. Kiran & Khalid (2018: 271) has a more distinctly dull brown pileus and larger basidiospores, (6–) 6.2–9.4 (–10.9) × (3.3–) 3.6–4.7 (‒4.8) μm ( Sattar et al. 2018). The phylogenetically close Rhodocollybia amica J. L. Mata & Halling (in Mata et al. 2004: 339) differs by more robust basidiomata (pileus 20–115 mm broad, stipe 50–90 × 4–8 mm), a pileus that is apricot gold at disc, a light brown stipe, a context with a fragrant or spicy odor, smaller basidiospores (4–6 × 2.4–3.6 μm) and smaller basidia‚ 18–21 × 4–5 μm ( Mata et al. 2004).

Rhodocollybia sp. (Hongcheon, Nae-myeon, Gwangwon-ri, 26 July 2007, R. Ryoo & H.J. Gong, Antonín 07.124, BRNM 714986) is phylogenetically close to R. hongneungensis . It differs by a pale orange-brown pileus and slightly smaller basidiospores, 6.5‒8.0 (‒8.2) × 3.0‒4.0 µm, average 7.4 × 3.2 µm. Macroscopically, it is more similar to R. butyraceoides or R. variabilicolor . Although it probably represents an undescribed taxon, having only one collection with only one basidioma, we refrain to formally describe it as a new species. Its sequence was not included in the phylogenetic tree, but the GenBank accession number was registered for future studies.

Key to species of Rhodocollybia species collected in the Republic of Korea

1. Pileus white, milky white, sometimes with rusty brownish tinge, rusty stained, not or only very slightly hygrophanous; basidiospores (5.0‒) 5.5‒6.5 × 4.0‒5.3 (‒5.5) µm, average 5.83 × 4.70 µm .......................................................................................... R. maculata

1*. Pileus coloured, never stained, hygrophanous; basidiospores larger, average> 7.0 µm in length ....................................................2

2. Pileus dirty ochre brown, greyish beige or greyish orange and drying out to pale dirty yellowish ochre; basidiospores 7.0‒8.5 × 3.5‒4.5 µm, average of length 7.84 µm; cheilocystidia rather small, 17‒32 × 4.0‒10 µm, cylindrical, clavate, (narrowly) fusoid, irregular, branched, lobate ..................................................................................................................................... R. hongneungensis

2*. Pileus darker, brownish orange to brown or reddish or greyish brown; basidiospores size on average shorter (<7.4 µm); cheilocystidia larger, 21‒50 (‒65) µm, irregular, branched to coralloid ............................................................................................3

3. Pileus 10‒45 mm broad; stipe 25‒65 × 1.5‒6 mm; basidiospores Q-value 2.04; branched to coralloid pileipellis terminal cells absent......................................................................................................................................................................... R. butyraceoides

3*. Pileus 15‒60 mm broad; stipe 40‒80 (‒100) × 3‒7 mm; basidiospores Q-value 1.82; branched to coralloid pileipellis terminal cells (mostly) present ......................................................................................................................................................... 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 7. Rhodocollybia hongneungensis (holotype).A. Cheilocystidia. B. Basidiospores. C. Pileipellis. Scale bar = 20 µm. Drawings by V. Antonín and R. Ryoo.