Gerronema rhizomorpha Ming Zhang & W. X. Zhang, 2025

Zhang, Wei-Xin, Deng, Wang-Qiu, Chang, Chang-Qing, Zhou, Ping, Lin, Min & Zhang, Ming, 2025, Three new species of Gerronema (Agaricales, Basidiomycota) from southern China, MycoKeys 114, pp. 239-258 : 239-258

Gerronema rhizomorpha Ming Zhang & W. X. Zhang sp. nov.

Figs 6 , 7

Diagnosis.

Distinguished from other Gerronema species by the combination characters of medium-sized basidiomata, yellowish white to brown pileus, well-developed rhizomorphs at stipe base, the absence of cheilocystidia, and pleurocystidia.

Holotype.

China • Guangdong Province: Fengkai County, Zhaoqing City, Heishiding provincial natural reserve ; 23°26'30"N, 111°53'28"E; 340 m asl.; 25 May 2023; Ming Zhang and Guo-Rui Zhong ( GDGM 92067 ).

Etymology.

rhizomorpha (Latin) , referring to the species, usually has long and well-developed rhizomorphs at stipe base.

Description.

Basidiomata medium-sized. Pileus 35–95 mm broad, hemispherical to plano-convex, depressed at center, brown (5 E 5–6) when young, yellowish white (2 A 2–3) to brown (5 E 4–5) at maturity, usually brown (5 E 4–5) to dark brown (6 F 4–5) at center, surface dry, distinctly radially striped with brown (5 E 6– 7,6E 4–5) lines, margin inflexed. Lamellae subdecurrent, subdistant, ventricose, even, white to yellowish white (1 A 1–2), with 1–3 lamellulae. Stipe 40–110 × 4–10 mm, central to eccentric, cylindrical, hollow, white to yellowish white (1 A 1–2), sometimes yellowish grey to greyish yellow (2 C 2–3) at the base, covered with yellowish grey to greyish yellow (2 C 2–4) fibrils, base with developed and white (1 A 1) rhizomorphs. Odor and taste not recorded.

Basidiospores 7–8.5 (9.5) × 5–6 (6.5) μm, L m = 7.80 ± 0.71 µm, W m = 5.53 ± 0.42 µm, Q = (1.23) 1.27–1.58 (1.6), Q m = 1.41 ± 0.13, broadly ellipsoid to ellipsoid, smooth, thin-walled, hyaline, guttulate, inamyloid. Basidia 25.5–32 × 7.5–11.5 μm, clavate, thin-walled, hyaline, 4 - spored, with sterigmata 2.8–6 µm long. Hymenial cystidia absent. Lamellar trama regular to subregular, hyphae 3–22 μm wide, thin-walled, hyaline. Pileipellis a cutis, hyphae 3–25 μm wide, thin-walled, light yellow in KOH; pileocystidia 25.5–63.5 × 6–14 μm, narrowly utriform to cylindrical, thin-walled, greyish brown to light brown pigmented in KOH. Pileus trama subregular, sarcodimitic. Stipitipellis a cutis, hyphae 1.5–11 μm wide, smooth, thin-walled, hyaline; caulocy stidia 12.5–33 × 3.5–8 μm, narrowly cylindrical to oblong, thin-walled, hyaline. Stipe trama regular, sarcodimitic. Clamp connections present in all tissues.

Habit and distribution.

Solitary or scattered, growing on the damp soil under broad-leaved forests. Currently known from China and Japan.

Additional specimen examined.

China • Guangdong Province: Shaoguan City, Nanling National Forest Park ; 24°56'48"N, 113°3'19"E; 490 m asl.; 9 June 2022; Ming Zhang, Guo-Rui Zhong, and Shi-Zheng Wang ( GDGM 87835 ) .

Figures

Figure 6. Basidiomata of Gerronema rhizomorpha A, B collection GDGM 92067, holotype C, D collection GDGM 87835. Photographed by Ming Zhang. Scale bars: 30 mm (A, B); 50 mm (C); 30 mm (D).

Figure 7. Microscopic features of Gerronema rhizomorpha (GDGM 92067, holotype) A Basidiospores B Basidia C Pileipellis D Stipitipellis. Scale bars: 10 mm (A, B); 50 mm (C, D).