Aureoboletus nanlingensis Ming Zhang, C.Q. Wang & T.H. Li, sp. nov.

Index Fungorum number: IF 900315;  Mycobank number: MB 900315; Facesoffungi number: FoF 14039; Fig. 1

Etymology – “nanling” refers to the type locality Nanling National Forest Park.

Holotype – GDGM71707.

Macroscopic characters – Basidiomes small-sized. Pileus 2–4.5 cm wide, hemispheric when young, becoming convex to nearly plane in age, fleshy, dry, subtomentose, grayish yellow to brownish orange (4C5–7C5), slightly paler toward pileus margin; margin thin, slightly incurved when young, becoming nearly straight in age, without veil remnants. Context 4–7 mm thick at center, firm and tough in youth, becoming soft, white, unchanging when exposed. Tubes 3–6 mm deep, pastel yellow, light yellow, greenish yellow to greyish yellow (1A4–1A2, 2A4–2A5, 1B4–2B4), unchanging when bruised. Pores small, 2–3 per mm, somewhat larger around the stipe, circular to angular, concolourous with tubes, unchanging when bruised. Stipe 40–60×8–10 mm, central, cylindrical or clavate, equal to slightly enlarged downwards, surface dry, yellowish white to pale yellow (1A2–2A2, 1A3–2A3), with obscure fibrous stripes. Stipe context white, unchanging or slightly changing greyish red when exposed, especially in the lower part. Basal mycelium white. Odour none. Taste mild.

Microscopic characters – Basidiospores 7–8.5 × (4–)4.5–5 µm, ( x = 7.7 × 4.7 μm, n = 20), ellipsoidal to broadly ellipsoidal, oblong in ventral view, smooth, yellowish to yellowish brown in 5% KOH, thin-walled. Basidia 25–30×8–10 µm, clavate, 4-spored, sterigmata 3–5 µm long, yellowish white to hyaline in 5% KOH, without basal clamps. Pleurocystidia 35–60 × 10–13 μm, fusiform, thin-walled. Cheilocystidia frequent, similar to pleurocystidia in shape and size. Hymenophoral trama subparallel, yellowish white to hyaline in 5% KOH, with 4–10 μm broad. Pileipellis a trichodermium of suberect hyphae 8–15 μm in diam, branched, yellowish white to hyaline in 5% KOH; terminal cells 40–70 × 8–15 µm, cylindrical, clavate or nearly fusoid. Stipitipellis a layer of repent hyphae 4–8 μm in diam, hyaline in 5% KOH. Clamp connections absent in all tissues.

Habit, habitat and distribution – Solitary to scattered on soil in broadleaf forest dominated by Fagaceae trees. Currently only known from southern China.

Material examined – China, Guangdong Province, Shaoguan, Nanxiong Town, Qingzhangshan-Xiaoliukeng Provincial Natural Reserve, alt. 500 m, 16 May 2018, Ming Zhang, GDGM71707 (holotype); ibid., alt. 580 m, 17 May 2018, Ming Zhang, GDGM44729.

GenBank numbers – GDGM71707: LSU = MN204556, RPB1= MN473174, RPB2= MN549710; GDGM44729: LSU=OP901643, TEF1-α=OP918151, RPB1=OP918157, RPB2=OP918154.

Notes – Aureoboletus nanlingensis is characterized by its dry, subtomentose and grayish yellow to brownish orange pileus, white context unchanging when exposed, light yellow to greyish yellow hymenophore unchanging when bruised, and ellipsoidal to broadly ellipsoidal basidiospores. The combination of above features corresponds to the define of “Clade II” of Aureoboletus in Zhang et al. (2019).

Figure 1 – Aureoboletus nanlingensis (GDGM71707, holotype). a, b Basidiomes. c Cheilocystidia. and pleurocystidia. d Basidia. e Basidiospores. f Pileipellis. Scale bars: a, b=5 cm, c–e=10 µm, f=20 µm