Aureoboletus solus 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 solus Ming Zhang & T.H. Li sp. nov. Figs 2, K, 3H, 8 A–D

Diagnosis.

This species can be easily distinguished from other Aureoboletus taxa by its dry and small basidiomata, brownish-yellow to greyish-red pileus, glabrous stipe and smaller basidiospores (7 –)8–10.5(– 11) × (4 –)4.5– 5 μm.

Etymology.

" solus " refers to the solitary habit.

Type.

China, Guangdong Province, Shaoguan City, Nanling National Nature Reserve, on soil under the broadleaf forest, dominated by Fagaceae trees, 16 June 2015, M. Zhang (holotype: GDGM44759).

Description.

Basidiomata small-sized. Pileus 1.5-2.5 cm wide, hemispheric when young, becoming convex to nearly plane in age, fleshy, dry or slightly viscid when wet, minutely velvet subtomentose, slightly wrinkled, brownish-yellow, brownish-orange, brownish-red to greyish-red (5C7-8C7, 5C5-9C5); margin thin, slightly incurved at first, becoming nearly straight, often appendiculate with small membranous remains of the veil. Context 2-6 mm thick at centre, firm and tough in youth, becoming soft, white, more or less greyish-red (9C5-11C5) to brownish-red (9C7-11C7) beneath the pileipellis, unchanging when exposed. Tubes 2-3 mm deep, gr-yish-yellow (1B5-3B5), light yellow (1A5-3A5) to vivid yellow (1A8-3A8), gradually changing to greenish-yellow when mature, unchanging when bruised, shallowly depressed around the stipe at maturity. Pores small, 1-2 per mm, somewhat larger around the stipe, circular to angular; pore-surface concolorous with tubes. Stipe 20-45 × 2-6 mm, central, cylindrical or clavate, equal to slightly enlarged downwards, glabrous, dry or slightly viscid when wet, pale orange to pale red (5A3-7A3), pastel red (8A5-10A5), with very pale flush of pastel red (8A5-10A5) fibrous stripes. Stipe context white to pastel red (8A4-10A4), slightly darker when bruised, especially in the lower part. Basal mycelium white. Odour none. Taste mild.

Basidiospores [80/3/3] (7 –)8–10.5(– 11) ×(4–)4.5– 5 μm, Q = (1.5 –)1.8–2.2(– 2.6), Qm = 2.0 ± 0.21, subfusiform and inequilateral in side view, oblong to ovoid in ventral view, smooth, yellowish to yellowish-brown in 5% KOH and yellow brown to dark brown in Melzer’s reagent, thin-walled. Basidia 1, 2, 4-spored 25-46 × 9-16 μm, clavate, yellowish-white to hyaline in 5% KOH; sterigmata 2-4.5 µm long. Pleurocystidia frequent, 38-66 × 11-15 μm, fusiform, thin-walled, yellowish-white to hyaline in 5% KOH. Cheilocystidia similar to pleurocystidia in shape and size. Hymenophoral trama composed of subparallel hyphae 5-11 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis an entangled trichodermium of erect hyphae 5-17 μm in diameter, branched, yellowish-white to hyaline in 5% KOH, dextrinoid in Melzer’s reagent; terminal cells cylindrical, clavate or nearly fusoid. Stipitipellis a layer of repent hyphae 4-23 μm in diameter, hyaline in 5% KOH. Caulocystidia infrequent. Clamp connections absent in all tissues.

Ecology and distribution.

Solitary or gregarious on soil under broadleaf forests dominated by Castanopsis spp. and Cyclobalanopsis spp. and mixed with other broadleaf trees, alt. 300-1200 m; May to July, currently only known from Guangdong Province.

Additional specimens examined.

China, Guangdong Province, Shaoguan City, Nangling National Nature Reserve, alt. 1200 m, 29 July 2017, M. Zhang (GDGM70342); Guangdong Province, Huizhou County, Xiangtoushan National Nature Reserve, alt. 400 m, 16 June 2016, J.P. Zou (GDGM46222); Guangdong Province, Huizhou City, Nankunshan Provincial Nature Reserve, alt. 700 m, 15 May 2013, M. Zhang (GDGM42822); Guangdong Province, Shaoguan City, Danxianshan National Nature Reserve, alt. 300 m, 3 June 2017, M. Zhang (GDGM46807), Same locality, 2 June 2017, M. Zhang (GDGM49404).

Notes.

Aureoboletus solus looks like A. tenuis ; however, the latter differs from the former in its viscid basidiomata, ixotrichodermial stipitipellis, composed of terminal hyphae with slightly swollen tips and larger basidiospores (10 –)11– 12 × 4-5 µm ( Zhang et al. 2014). Phylogenetic analyses indicated that A. solus is closely related to A. nephrosporus , but A. nephrosporus differs in having larger basidiomata with a red to brownish-red pileus, ovoid to nephroid basidiospores 8-10.5 × 5-6 µm and cheilocystidia and pleurocystidia covered with a thick layer of a strongly refractive pale yellow substance ( 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.