Gymnopus alliifoetidissimus T.H. Li & J.P. Li, 2021

Li, Ji-Peng, Li, Yu, Li, Tai-Hui, Antonín, Vladimír, Hosen, Md Iqbal, Song, Bin, Xie, Meng-Le & Feng, Zhan, 2021, A preliminary report of Gymnopus sect. Impudicae (Omphalotaceae) from China, Phytotaxa 497 (3), pp. 263-276 : 267-271

Gymnopus alliifoetidissimus T.H. Li & J.P. Li , sp. nov. ( FIGURES 2a–b and 3 )

MycoBank MB#834781

Diagnosis:—Similar to G. stenophyllus , but different in its garlic odour and inconspicuous cheilocystidia with or without finger-like apical projection(s) or with more or less coralloid apex; characterized mainly by the gregarious habit on decayed twigs in broad-leaf forest, wholly white marasmielloid basidiomata, ellipsoid to sublacrymoid basidiospores sized 6–7 × 3–4 μm, and inconspicuous cheilocystidia.

Typification:— CHINA, Guangdong Province, Zhaoqing City, Dinghushan Biosphere Reserve , 23° 09’ 65” N, 112° 32’ 06” E, alt. 87 m, 12 July 2019, J. P . Li , M . Zhang & H. S . Wen ( GDGM 76695 !, holotype) .

Etymology:—The epithet “ alliifoetidissimus ” (Lat.) refers to the strong alliaceous foetid smell of the basidiomata.

Description:—Basidiomata gregarious, marasmielloid. Pileus 4–18 mm broad, convex to plano-convex, expanding to applanate or plano-concave, slightly depressed at the centre, hygrophanous, glabrous, striate from the margin up to 2/3 of the radius or nearly to the centre when applanate, white overall, sometimes with orange to brownish orange (6A7–6C7) tinct around disc; context thin, white. Lamellae free to narrowly adnate, linear to ventricose, white when fresh, white to pale orange (4A3) when dry, sometimes slightly orange to pale orange (5A2–5A3) at the margin when fresh, becoming yellowish white (4A2) to greyish yellow (4A5) or brownish orange (5A6) at the margin when dry, L = 10–15, l = 1–3. Stipe 6–13 mm long, 0.5–3 mm thick at the apex, 0.5–1 mm thick at the base, cylindrical or compressed, hollow, insititious, central, minutely scaly or furfuraceous, concolorous with the pileus when fresh, yellowish white (1A2) when dry, sometimes slightly orange to pale orange (5A2–5A3) at the base when fresh, becoming greyish orange (5B5) to brownish orange (5C5) when dry. Odour alliaceous, strong.

Basidiospores 6–7 × 3–4 μm (average = 7.0 × 3.1 μm, n = 40, E = 1.75–2.67, Q= 2.49), ellipsoid to sublacrymoid, smooth, hyaline, thin-walled. Basidia 20–28.5 × 5–6.5 μm, clavate, 4-spored, hyaline. Basidioles 17–27.5 × 4–6.5 μm, cylindrical to clavate, rarely branched or diverticulate. Cheilocystidia 10–33 × 2–8 μm, irregularly cylindrical, clavate, inconspicuous, hyaline, with or without finger-like apical projection(s), or more or less coralloid at apex. Pleurocystidia absent. Pileipellis a cutis composed of cylindrical hyphae which are thin-walled, hyaline, diverticulate, and up to 5.5 μm wide; Rameales -structure rarely present; terminal cells cylindrical, obtuse, smooth, slightly coralloid at the apex. Stipitipellis a cutis composed of cylindrical hyphae, which are slightly thick-walled, smooth, non-dextrinoid, parallelly arranged, and up to 12 μm wide. Caulocystidia 13–53 × 3.5–7 μm, cylindrical, slightly irregular, sometimes branched or with projection(s), thin-walled. Clamp connections present.

Habitat: —Saprotrophic, gregarious on decayed twigs or small branches in broad-leaf forests.

Remarks:— Gymnopus alliifoetidissimus has a strong smell, inconspicuous cheilocystidia, and a pileipellis as a cutis made up of diverticulate elements. These morphological characteristics are consistent with the concept of G. sect. Impudicae ( Antonín & Noordeloos 2010).

Among the known species of Gymnopus sect. Impudicae , none of them is similar to the new species in morphology. However, considering the identity and section affiliation of some similar white species, especially those only described in old literature, are not fully known, they should be compared with the new species as follows: Gymnopus albus ( Peck 1888: 62) Murrill (1916: 355) , G. ludovicianus Murrill (1916: 355) , G. microsporus ( Peck 1895: 486) Murrill (1916: 355) , G. sphaerosporus M. Villarreal, Arenal & G. Moreno in Arenal et al. (2006: 30), G. stenophyllus ( Montagne 1854: 116) J.L. Mata & R.H. Petersen in Mata et al. (2004: 221) and G. subflavescens Murrill (1916: 373) have white or almost similarly coloured basidiomata with the new species. However, all these species are without unpleasant odour. Moreover, G. albus can be distinguished by its adnexed or nearly free lamellae, the stipe length (25 mm) more longer than the pileus diameter (6–10 mm) and smaller basidiospores (3–4 × 4–5 μm, Murrill 1916); G. ludovicianus has cinnamon-coloured, intervenose, sometimes subdecurrent lamellae, clavate or sphaeropedunculate cheilocystidia and a hymeniform pileipellis of Globulares - type elements ( Murrill 1916; Desjardin 1989), therefore it should belong to Marasmius sect. Globulares Kühner (1933: 100) ; G. microsporus can be distinguished by its smaller basidiospores (3 × 4 μm), and brown lamellae and stipe when dry ( Murrill 1916); G. sphaerosporus differs in its eccentric to nearly lateral stipe, larger (7–7.95–9 × 6.5–7.54–8.5 µm) subglobose basidiospores and a trichoderm stipitipellis ( Arenal et al. 2006); G. stenophyllus , originally described as Marasmius stenophyllus Mont. ( Montagne 1854) , differs by its venose lamellae and globose basidiospores. However, M. stenophyllus was considered as a member of Marasmiellus ( Singer 1961) , and richer information with the amendment was provided after studies of the type specimen ( Singer 1973). Although the newer description by Singer (1973) showed a very similar sized and shaped basidiospores (6.8–8 × 2.7–3.5 µm) to the new species, it can be distinguished by its white to pale isabelline pileus and differently shaped cheilocystidia; and what is more, the phylogenetic analysis by Mata et al. (2004) indicated that it is not a member of G. sect. Impudicae but belongs to the G. sect. Vestipedes. And G. subflavescens differs from the new species in its pileus with a floccose subseparable pellicle ( Murrill 1916).

Among the taxa of macromorphologically similar genera Marasmius , Marasmiellus and Mycetinis , there also are some species with a similar odour as the new species, but they can be distinguished as follows. In Mycetinis , My. ignobilis (Berk. & Broome 1875: 40) Desjardin & B.A. Perry (2017: 1346) , with a white or almost similar coloured basidiomata, can be easily distinguished by its strongly eccentric to nearly lateral stipe ( Desjardin & Perry 2017). Among the species of Marasmius with a garlic odour, M. alliarius Petch (1948: 43) , M. alliifoetidus Corner (1996: 29) and M. alliipotens Corner (1996: 29) can be easily distinguished from the new species by their dark pileus; while M. alliodoratissimus Garrido (1988: 208) has a different habitat on leaf in Nothofagus woodland in South America; and M. allium Eichelb. (1906: 64) differs in its conchoidal pileus and a very short lateral stipe. Among the species of Marasmiellus with a garlic odour, Ma. alliiodorus (Mont. 1835: 349) Singer (1962: 382) also has white basidiomata and seems to be very similar to the new species, but it can be distinguished by its larger basidiospores (6.7–10 × 4.7– 5.3 µm, Singer 1973); Ma. subingratus ( Dennis 1951: 427) Singer (1955: 389) and Ma. osmophorus Dennis (1961: 89) are distinctive by their dark basidiomata ( Singer 1973). Of course, if having their DNA sequences compared, these species will be easier to distinguish from the new species because they belong to different genera and have quite distant phylogenetic relationships.

Gymnopus densilamellatus Antonín, R. Ryoo & K.H. Ka in Ryoo et al., Phytotaxa 268(2): 78, 2016. ( FIGURES 2c, d and 4 )

Description:—Basidiomata gregarious. Pileus 16–42 mm broad when dry, hemispherical when young, becoming convex or plano-convex, with a distinct central umbo or slightly depressed centre, then slightly inflexed at margin, surface smooth, radially fibrillose, hygrophanous when young, not translucently striate, almost glabrous, brownish orange to light brown (6C5–7D7), pale orange to orange (5A3–6A6) at the centre and whitish towards the margin. Lamellae very close, free or emarginate, white then yellowish white (4A2) to orange white (5A2), yellow in some places. Stipe 32–62 × 2–8 mm when dry, cylindrical, slightly enlarged at the apex (2–8 mm), 1.5–6 mm thick at the centre, equal or to more or less enlarged at the base (3–8 mm), straight or sometimes curved, longitudinally striate, finely tomentose, more densely downwards the base, glabrescent towards the apex, whitish with yellowish brown (5D8) tinct in some places, white at the apex and white or somewhat greyish rose (12B3–4) towards base; with a white basal mycelium. Odour unpleasant.

Basidiospores 5–7 (‒8) × 2.5–3 (‒3.5) μm, (average = 6.0 × 2.9 μm, n = 40, E = 1.67–2.33 (‒2.80), Q = 2.12), ellipsoid, sublacrymoid, hyaline, thin-walled. Basidia 18–24 × 5.5–7 μm, 4-spored, clavate, hyaline. Basidioles 17–24 × 3–6 μm, cylindrical, clavate. Cheilocystidia 13–30 × 3–6 μm, cylindrical, narrowly clavate, irregular, with or without projections, thin-walled. Pleurocystidia absent. Pileipellis a cutis composed of radially arranged, cylindrical, mostly incrusted (zebroid), non-dextrinoid, 2.5‒10 μm wide hyphae with or without lateral projections. Stipitipellis a cutis composed of cylindrical, parallelly arranged, slightly thick-walled, smooth, non-dextrinoid, up to 6 μm wide hyphae; terminal cells cylindrical, slightly coralloid at the apex, obtuse, smooth or incrusted. Caulocystidia 35–70 × 4–13 μm, cylindrical, narrowly clavate, slightly irregular, sometimes branched or with projection(s), thin-walled. Clamp connections present.

Habitat: —On the debris or ground covered with pine needles in coniferous or mixed forests.

Material studied: — CHINA, Jilin Province, Shulan City, Qunling Tree Farm , 44° 18’ 46” N, 126° 58’ 37” E, alt. 250 m, 3 July 2016, M. L . Xie ( HMJAU 49126 ) . Heilongjiang Province, Yichun City, Qianwei Tree Farm , 49° 3’ 15” N, 129° 35’ 40” E, alt. 290 m, 9 August 2016, M. L . Xie ( HMJAU 49127 ) . Shanxi Province, Xinzhou City, Mt. Wutai , 39° 1’ 21” N, 113° 36’ 14” E, alt. 1800 m, 27 July 2019, M. L . Xie ( HMJAU 49128 ) .

Remarks:— Gymnopus densilamellatus is a very distinctive species originally described from South Korea and characterized by a brown to reddish brown (7–8D–E6–7) pileus that becomes paler with age, very close lamellae and a rotten cabbage-like or garlic smell ( Ryoo et al. 2016). The Chinese collections also have a more or less brown pileus which can change to paler with age, very close lamellae and an unpleasant odour. They are very similar to the specimen from the type locality according to the original description, only differing in the slightly smaller basidiospores ( Ryoo et al. 2016). Besides, the Chinese collections have nearly the same size of basidiospores as reported for another South Korean collection BRNM 714927 ( Ryoo et al. 2016). The phylogenetic analyses further confirmed that they are the same species, supporting that the Chinese collections can represent a new record to China.

Figures

FIGURE 2. Basidiomata of Gymnopus species. a–b. Gymnopus alliifoetidissimus (GDGM 76695!, holotype), c–d. G. densilamellatus (c. HMJAU 49127, d. HMJAU 49128), e–g. G. similis (GDGM 78308). a–b: photographed by J.P. Li, c–d: photographed by M.L. Xie, e–g: photographed by Z. Feng.

FIGURE 3. Microscopic features of Gymnopus alliifoetidissimus (GDGM 76695, holotype!). a. Basidiospores, b. Basidia, c. Basidioles, d. Cheilocystidia, e. Caulocystidia, f. Pileipellis terminal cells (Rameales-structure). Scale bars = a–e = 10 μm, f = 20 μm.

FIGURE 4. Microscopic features of G. densilamellatus (HMJAU 49127). a. Basidiospores, b. Basidia, c. Basidioles, d. Cheilocystidia, e. Caulocystidia, f. Pileipellis terminal cells. Scale bars, a–d = 10 μm, e–f = 20 μm.