Acyanoboletus rugosipileus G. Wu & Xin Zhang, 2025

Zhang, Xin, Li, Guangmei, Wang, Yuhang & Wu, Gang, 2025, A new species of the subfamily Suillelloideae (Boletaceae, Boletales) from China, Phytotaxa 689 (2), pp. 204-212 : 208-210

Acyanoboletus rugosipileus G. Wu & Xin Zhang , sp. nov. Figs 1–3

MycoBank no.: MB 855083

Diagnosis: Distinguished from other species of Acyanoboletus by its rugose pileus surface and additionally differs from A. controversus by longer basidiospores, and differs from A. dissimilis (E. Horak & G. Wu 2023: 755) by the larger basidioma and nearly glabrous stipe.

Holotype: CHINA, Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Mengla County, Xishuangbanna National Natural Reserve , elev. 1030 m, 6 July 2014, Gang Wu 1259 ( HKAS88996 ).

Gene sequences ex-holotype: PQ514134 (ITS), PQ517512 (nrLSU), PQ536872 ( TEF 1), PQ536877 (RPB 1), PQ536882 (RPB 2).

Etymology: rugosipileus (Lat.) , in reference to the rugose pileus of this species.

Pileus 4–9 cm diam., convex to broadly convex, surface usually rugose when mature; olive brown (4E8–4C4), chamois to bamboo yellow (4C4–4C5), brownish orange (5C4–5C5), light brown (5D4–5D5), sometimes paler in the margin, slightly viscid when wet, sterile margin present and often involute; context 9–11.5 mm thick, light yellow (4A4), yellowish white to pale yellow (1A2–1A3), unchanging upon exposure. Hymenophore sinuate, 3.5–11 mm thick; surface and tubes concolorous, pale yellow to pastel yellow (2A3–2A4) when young, wax yellow to absinthe yellow (3B5–3C5) in age, unchanging when bruised; pores roundish, 2 per mm. Stipe 6–9 cm long, 0.7–1.4 cm diam., central, subcylindrical, curved, firm, solid; surface dull yellow to straw yellow (3B3–3B4), golden yellow to grayish orange (5B6–5B7), often with brown tinge, covered with darker granules, sometimes with indistinctive reticulations or longitudinal striations on the upper part, unchanging when touched; context firm, pale yellow mixed with dull yellow, unchanging on exposure. Basal mycelium milky white.

Basidiospores (9.5) 10–12 (12.5) × (4) 4.5–5.5 μm [Q = (1.85) 1.89–2.55 (2.93), Q m = 2.18 ± 0.20], fusiform and inequilateral in side view, with suprahilar depression, fusiform in face view, yellowish, smooth, thin-walled. Basidia 26–45 × 8.5–12.5 μm, broadly clavate, 4-spored, rarely 2-spored, sterigmata up to 4.5 µm long. Cheilocystidia 33–60 × 7–10 μm, abundant, subfusoid to lanceolate, with short to long beaks, thin-walled. Pleurocystidia 32–86 × 6–14 μm, scattered, subfusoid, lanceolate to broadly ventricose, with short to long beaks, thin-walled. Hymenophoral trama boletoid, 4.5–10 μm wide. Pileipellis an intricate trichoderm to interwoven subcutis, about 150 μm thick, composed of filamentous hyphae 4–7 μm wide, thin-walled, with subcylindrical terminal cells 20–77 × 4–8 μm, thin-walled. Pileal trama composed of interwoven hyphae 4–10 μm wide. Stipitipellis 60–90 μm thick, hymeniform with short-clavate terminal cells (17.5–31 × 6–13 μm). Stipe trama composed of longitudinally arranged parallel thin-walled hyphae 4–14 μm wide. Clamp connections absent.

Habitat and distribution:—On soil in broad-leaved forests dominated by Fagaceae trees ( Lithocarpus spp. , Castanopsis spp. , etc.). May to July. Currently only known in tropical to subtropical regions of China.

Additional specimens examined:— CHINA, Guangdong Province: Shenzhen City, 2 May2024, SF1443724056718- 3 ( HKAS 136929 ). Chongqing Municipality, Beipei District , 30 June 2024, SF1448175774620-4 ( HKAS 144431 ) ; ibid., Jiangjin District , 4 July 2024, Xuemei Li YT 7476700591476-6 ( HKAS 144429 ) ; ibid., Jiangjin District , 25 June, Haolong Zeng & Chuan Xing SF 1448335984750-3 ( HKAS 144430 )

Figures

FIGURE 1. Maximum likelihood phylogenetic tree of the genus Acyanoboletus and allied genera in the subfamily Suillelloideae inferred from the nucleotide sequences of nrLSU, TEF1, RPB1 and RPB2. Bootstrap values (≥ 50%) and posterior probabilities (≥ 0.90) are shown on or beside supported branches. The clades of the genus Acyanoboletus is highlighted in a grayish box and the new species Acyanoboletus rugosipileus is shown in blue.

FIGURE 2. The habitat (A) and fresh basidiomata (B–I) of Acyanoboletus rugosipileus. (A–D: HKAS 88996; E–F: HKAS144430; G–I: HKAS144429).

FIGURE 3. Microscopic features of Acyanoboletus rugosipileus (A: HKAS 136929; B–G: HKAS 88996, holotype). A: Pileipellis; B: Basidia; C: Basidiospores; D: Pleurocystidia; E: Basidia, pleurocystidium, and basidioles; F: Cheilocystidia; G: Stipitipellis. Bars: 10 μm.