Gerronema microcarpum Q. Na, H. Zeng & Y.P. Ge, 2022

Na, Qin, Hu, Yaping, Zeng, Hui, Song, Zhizhong, Ding, Hui, Cheng, Xianhao & Ge, Yupeng, 2022, Updated taxonomy on Gerronema (Porotheleaceae, Agaricales) with three new taxa and one new record from China, MycoKeys 89, pp. 87-120 : 87

Gerronema microcarpum Q. Na, H. Zeng & Y.P. Ge sp. nov.

Figs 5 , 6 , 7

Diagnosis.

Basidiomata distinctly small. A pileus a bit slimy when moist. Stipe light yellow, base turning to light brown with age. Cheilocystidia common in clavate with rounded apex, rarely fusiform. Pileipellis occasionally with coarse excrescences.

Holotype.

China. Zhejiang Province, Lishui City, Qingtian County, Shigu Lake, 6 Aug 2021, Qin Na, Yupeng Ge, Junqing Yan, Zewei Liu, and Yulan Sun, FFAAS0373 (collection no. MY0526).

Etymology.

Refers to the small basidiomata.

Description.

Pileus 1.5-9.0 mm in diam., at first convex, later applanate in the marginal zone, infundibuliform or deeply umbilicate in the center when old, grayish yellow (2B2) to shallow yellowish brown (2C4), shallowly sulcate, translucent-striate, smooth, a bit slimy when moist, but not hygrophanous. Context yellowish white (2A2), thin. Lamellae close to moderately close, shortly decurrent when young, whitish yellow (1A2), decurrent to deeply decurrent when old, concolorous with the sides. Stipe 5.0-18.0 × 1.0-2.0 mm, hollow or soon becoming hollow, generally central, equal or with slightly broader base, light yellow (2A2), becoming light brown (5C6) towards the base, pruinose, glabrescent when old, base covered with a few white fibrils. Odor and taste indistinctive.

Basidiospores [140/7/6] (6.1) 6.3-6.8-7.2 (7.5) × (3.3) 3.5-3.8-4.1 (4.3) μm [Q = 1.64-1.95, Q = 1.80 ± 0.059] [holotype [40/2/1] (6.1) 6.2-6.7-7.3 (7.5) × 3.4-3.7-4.1 (4.3) μm, Q = 1.64-1.95, Q = 1.81 ± 0.066], narrowly ellipsoid to cylindrical, hyaline in water and 5% KOH, inamyloid, smooth. Basidia 25-33 × 6-8 μm, 4-spored, clavate, hyaline. Cheilocystidia common in clavate with rounded apex, 31-35 × 5-8 μm, rarely fusiform, thin-walled and hyaline. Pleurocystidia not seen. Lamellar trama subregular; hyphae 2-5 μm wide, thin-walled, hyaline, inamyloid. Pileus trama subregular, sarcodimitic. Pileipellis a cutis, hyphae 3-6 μm wide, light yellow (2B2); terminal elements clavate, utriform, occasionally with coarse excrescences, 19-43 × 4-6 μm, light yellowish brown (2C4) to yellowish brown (2D4) pigment in KOH; true pileocystidia absent. Hyphae of the stipitipellis 2-6 μm wide, hyaline, smooth; caulocystidia long cylindrical or clavate, 26-65 × 4-9 μm, hyaline, thin-walled. All tissues nonreactive in iodine. Clamps present in all tissues.

Habit and habitat.

Scattered on rotten wood and twigs in mixed evergreenbroadleaf forests consisting of species of Fagaceae , Lauraceae , Theaceae , Ericaceae , Symplocaceae , Pinaceae , etc. Subtropical monsoon climate or subtropical humid climate.

Other specimens examined.

Anhui Province, Chizhou City, Shitai County, Dayan Village, Guniujiang National Natural Reserve, 31 Aug 2019, Qin Na, Yupeng Ge, Hui Zeng, Liangliang Qi, and Junqing Yan, FFAAS0365 (collection no. MY0259); Fujian Province, Nanping City, Wuyi Mountain, 25 Jul 2020, Qin Na, Yupeng Ge, Yaping Hu, Hui Zeng, and Zewei Liu, FFAAS0375 (collection no. MY0544); Zhejiang Province, Hangzhou City, Tianmu Mountain, 30 Jul 2021, Qin Na, Yupeng Ge, Zewei Liu, and Yulan Sun, FFAAS0371 (collection no. MY0424); Lishui City, Liandu District, Baiyun National Forest Park, 2 Aug 2021, Qin Na, Yupeng Ge, Zewei Liu, and Yulan Sun, FFAAS0372 (collection no. MY0478), Qingtian County, Shigu Lake, 6 Aug 2021, Qin Na, Yupeng Ge, Junqing Yan, Zewei Liu, and Yulan Sun, FFAAS0374 (collection no. MY0527).

Remarks.

Characteristics such as tiny omphalinoid basidiomata, decurrent lamellae, inamyloid and narrowly ellipsoid to cylindrical basidiospores, sarcodimitic tramal tissues, a pileipellis with pigmented terminal elements, and long cylindrical or clavate caulocystidia support the placement of this species in Gerronema ( Singer 1970, 1986; Norvell et al. 1994). Because of its small basidiomata, decurrent lamellae, and subregular pileus trama, G. kuruvense is difficult to distinguish from G. microcarpum , but its pileus is orange yellow all over, no cheilocystidia or pleurocystidia are present, and its pileocystidia and caulocystidia are somewhat thick-walled ( Latha et al. 2018). Gerronema nemorale has certain morphological similarities to G. microcarpum , namely, the presence of tiny yellowish basidiomata, decurrent lamellae, and cylindrical basidiospores ( Antonín et al. 2008, 2011; Takashi 2009). However, G. nemorale differs in having a pileus with an olive tint, a longer stipe with conspicuous white mycelioid bristles, and larger terminal elements of the pileipellis (up to 150 μm) ( Antonín et al. 2008, 2011; Takashi 2009). Compared with G. microcarpum , G. subchrysophyllum (Murrill) Singer has an olive-umber pileus fading to grayish when old, larger and ellipsoid basidiospores (4.3-8.5 × 2.5-6.3 μm), and sometimes basidiole-like cheilocystidia ( Singer 1970). Gerronema keralense and G. strombodes are easily mistaken for G. microcarpum , but both the two closely related species are distinguishable by their absence of cheilocystidia or their partially thick-walled pileipellis and stipitipellis ( Singer 1970; Antonín et al. 2008; Latha et al. 2018; Kim et al. 2014).

Figures

Figure 5. Fresh basidiomata of Gerronema microcarpum Q. Na, H. Zeng & Y. P. Ge. a FFAAS 0365 b FFAAS 0372 c-d FFAAS 0375 e FFAAS 0373 (Holotype) f-g FFAAS 0374 h-i FFAAS 0371. Scale bars: 10 mm (a-i). Photographs a, e-i by Yupeng Ge; b by Junqing Yan; c-d by Qin Na.

Figure 6. Microscopic features of Gerronema microcarpum Q. Na, H. Zeng & Y. P. Ge. (FFAAS 0373, Holotype) a-e basidiospores f basidia g-i cheilocystidia j lamellar trama k pileipellis l stipitipellis and caulocystidia. Scale bars: 5 μm (a-e); 10 μm (f-l).

Figure 7. Morphological features of Gerronema microcarpum Q. Na, H. Zeng & Y. P. Ge. (FFAAS 0373, Holotype) a basidiomata b basidia c basidiospores d cheilocystidia e stipitipellis and caulocystidia f pileipellis. Scale bars: 10 mm (a); 10 μm (b, d-f); 5 μm (c). Drawing by Qin Na and Yupeng Ge.