Aureoboletus glutinosus Ming Zhang & T.H. Li

Zhang, Ming, Li, Tai-Hui, Wang, Chao-Qun, Zeng, Nian-Kai & Deng, Wang-Qiu, 2019, Phylogenetic overview of Aureoboletus (Boletaceae, Boletales), with descriptions of six new species from China, MycoKeys 61, pp. 111-145 : 111

Aureoboletus glutinosus Ming Zhang & T.H. Li sp. nov. Figs 2A, B , 3A , 4 A–E

Diagnosis.

This species is distinguished from other Aureoboletus taxa by its smaller and glutinous basidiomata, reddish-brown to ruby pileus usually with irregular reticulation and darker folds, gelatinised veil remnants and smooth basidiospores 10-13.5 × 4.5-5 µm in size.

Etymology.

" glutinosus " refers to the glutinous basidiomata.

Type.

China, Hunan Province, Rucheng Town, Jiulongjiang National Forest Park, on soil and usually growing amongst the mosses under the broadleaf forest, at 25°38'N, 113°77'E, alt. 300 m, 8 May 2014, M. Zhang (holotype: GDGM44477).

Description.

Basidiomata small-sized. Pileus 1-2 cm wide, obtuse to convex, becoming broadly convex to plane, fleshy, viscid, especially when young and wet, reddish-brown, violet brown to greyish-ruby (9E6-12E6, 9E7-12E7), slightly fading to pale yellow (2A3-4A3) towards margin, usually forming a pale yellow to even nearly white zone at margin, distinctly wrinkled and often reticulate irregularly with somewhat darker folds at centre, strongly glutinous or mucilaginous when fresh; margin somewhat involute to nearly flat, often attached with yellowish-white to subhyaline and strongly gelatinised veil remnants. Context 2-5 mm thick at stipe, firm and tough in youth, soft when matured, white on the whole, greyish-red (10B5-11B5) beneath pileipellis, practically unchanging to becoming slightly greyish-pinkish or greyish-red (10B5-11B5) when exposed. Tubes 7-10 mm deep, distinctly depressed around stipe, yellowish-white (2A2-4A2) when young, becoming pale yellow, greyish-yellow, pastel yellow to olive yellow (2A3-4A3, 1B3-2B3, 2A4-3A4, 2C6-3C6) with age, often with an olive tint, unchanging when bruised. Pores 0.3-0.5 mm in diam., mostly subangular, slightly radially elongated around stipe at maturity, smaller near pileus margin, concolorous with tubes. Stipe 15-40 × 2-4 mm, central, cylindrical or narrowly clavate, solid, equal to slightly tender downwards, greyish-orange (6B4), greyish-red (7B4) to brownish-orange (6C4-7C4), without reticulation, smooth to faintly longitudinally striate, gelatinous or strongly viscid when young and wet, usually covered with a mucilaginous layer, with white basal mycelium. Odour not distinct. Taste mild.

Basidiospores [150/4/4] (9.5 –)10– 13.5 × (4 –)4.5– 5 µm, Q = (2.2 –)2.3–2.5(– 2.7), Qm = 2.48 ± 0.18, subfusiform and inequilateral in side view, oblong in ventral view, smooth, yellowish to yellowish-brown in 5% KOH and yellow brown to dark brown in Melzer’s reagent, thin-walled. Basidia 20-30 × 7-10 µm, clavate, 4-spored, sterigmata 2-4.5 µm long, yellowish-white to hyaline in 5% KOH, without basal clamps. Pleurocystidia 35-60 × 8-13 μm, fusiform, thin-walled. Cheilocystidia frequent, similar to pleurocystidia in shape and size. Hymenophoral trama composed of subparallel hyphae 4-10 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis an ixotrichodermium of erect hyphae 5-12 μm in diameter, branched, yellowish-white to hyaline in 5% KOH, dextrinoid in Melzer’s reagent; terminal cells 27-50 × 7-12 µm, cylindrical, clavate or nearly fusoid. Stipitipellis a layer of repent to suberect branching hyphae 3-6 μm in diam., hyaline in 5% KOH. Clamp connections absent in all tissues.

Ecology and distribution.

Solitary or scattered on ground with humus and debris, usually growing amongst the mosses ( Fissidens sp. and Pottiaceae sp.) under Fagaceae , mixed with other broadleaf trees, alt. 300-500 m; May to July, known from Guangdong and Anhui Province.

Additional specimens examined.

China, Hunan Province, Chenzhou City, Rucheng Town, Jiulongjian National Forest Park, 8 May 2014, H. Huang (GDGM44476); Same location, 12 June 2015, M. Zhang (GDGM44733); Anhui Province, Huangshan City, Huangshan National Forest Park, 27 July 2015, C.H. Li (GDGM44821).

Notes.

Phylogenetic analyses showed that A. glutinosus is closely related to A. marroninus , A. tenuis , A. thibetanus and A. viscidipes ; however, the independent phylogenetic position and different morphological characters can distinguish A. glutinosus from these similar species. Aureoboletus marroninus differs in having a more wrinkled and darker (violet brown or maroon) pileus, white context and smaller basidiospores 8.5-10 × 4-4.5 µm ( Zhang et al. 2014). Aureoboletus tenuis has relatively larger basidiomata (pileus up to 3.5 cm broad) usually lacking well-developed veil remnants on pileus margin, smaller basidiospores 11-12 × 4-5 μm and ixotrichodermial stipitipellis composed of terminal hyphae with swollen tips ( Zhang et al. 2014). Aureoboletus thibetanus is readily separated by its more robust basidiomata (pileus up to 5 cm broad), white ridged reticulation on pileus surface, white stipe and yellowish granular encrustation on cystidia and only known from the temperate zone in southwest China ( Patouillard 1895; Yang et al.2003; Klofac 2010). Aureoboletus viscidipes differs in having a brownish to brown pileus tinged with yellowish-white, a longer (up to 4 cm long) and nearly white stipe and a thick layer of a reflective pale-yellow substance on the surface of cheilocystidia and pleurocystidia ( Wu et al. 2016).

Figures

Figure 2. Basidiomata of six new species and one new combination of Aureoboletus from China. A, B A. glutinosus (A GDGM 44476 B GDGM 44477, holotype) C A. griseorufescens (GDGM 28490, holotype) D, E A. miniatoaurantiacus (D GDGM 43439 E GDGM 43282) F, G A. raphanaceus (F GDGM 45911, holotype G GDGM 52890) H, I A. sinobadius (H GDGM 44732 I GDGM 71932, holotype) J, K A. solus (GDGM 44759, holotype) L A. velutipes (L GDGM 44713, holotype). Scale bars: 2 cm.

Figure 3. Scanning electron micrograph of basidiospores of six new species and one new combination of Aureoboletus from China. A A. glutinosus (GDGM 44477, holotype) B A. griseorufescens (GDGM 28490, holotype) C, D A. miniatoaurantiacus (C GDGM 43439 D GDGM 4855) E, F A. raphanaceus (GDGM 45911, holotype) G A. sinobadius (GDGM 71932, holotype) H A. solus (GDGM 44759, holotype) I A. velutipes (GDGM 44713, holotype). Scale bars: 5 µm.

Figure 4. Aureoboletus glutinosus. A Basidiospores B Cheilocystidia and pleurocystidia C Basidia and pleurocystidia D Pileipellis E Stipitipellis. Scale bars: 10 µm (A-C); 20 µm (D, E).