Aureoboletus griseorufescens 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 griseorufescens Ming Zhang & T.H. Li sp. nov. Figs 2C , 3B , 5 A–E

Diagnosis.

This taxon can be distinguished from other Aureoboletus species by its brownish-orange to ruby pileus colour, white to yellowish-white context changing to greyish-red or greyish-rose when exposed, light yellow tubes and comparatively small basidiospores 9-10.5 × 4.5-5 μm.

Etymology.

" griseorufescens " refers to the greyish-red discolouration of context when exposed or bruised.

Type.

China, Guangdong Province, Shaoguan City, Chebaling National Natural Reserve, on soil under the broadleaf forest dominated by Fagaceae trees, alt. 300 m, 23°22'N, 113°42'E, 15 July 2008, C.Y. Deng (holotype: GDGM28490).

Description.

Basidiomata small to medium-sized. Pileus 2-5 cm wide, hemispheric when young, becoming convex to nearly plane in age, fleshy, subviscid or slightly viscid when wet, glabrous to minutely velvet-subtomentose, slightly wrinkled to rugulose, even or nearly so at margin, brownish-orange, brownish-red, dark red to greyish-ruby (6C6-7 to 11C6-7). Context 3-6 mm thick at centre, firm and tough, white to yellowish-white (2A1-2 to 3A1-2), more or less greyish-red (9C4-11C4) beneath the pileipellis and browner at the border line adjacent to tubes, gradually changing to greyish-red (9C4-11C4) to greyish-rose (12B5) when exposed. Tubes 2-4 mm deep, light yellow, yellow, pastel yellow to greenish-yellow (2A5, 3A4-6), unchanging when bruised. Pores small, 1-2 per mm, circular to angular, somewhat relatively larger and shallowly depressed around the stipe at maturity, concolorous with tubes, unchanging when bruised. Stipe 35-60 × 4-10 mm, central, cylindrical or clavate, equal to slightly enlarged downwards, smooth, viscid in wet condition, concolorous with pileus, pale in the apex. Stipe context white to reddish-white (9A2-11A2), gradually changing to greyish-red (9C4-11D5) to greyish-rose (12B5) when exposed, especially in the lower part. Basal mycelium white. Odour none. Taste mild.

Basidiospores [50/2/2] (8 –)9–10.5(– 11) × (4 –)4.5–5(– 5.5) μm, Q = (1.8 –)2– 2.2 (2.6), Qm = 2.19 ± 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 4-spored 25-30 × 7-11 μm, clavate, yellowish-white to hyaline in 5% KOH, sterigmata 2-3 μm. Cheilocystidia infrequent. Pleurocystidia 43-70 × 8-13 μm, fusiform, thin-walled, yellowish-white to hyaline in 5% KOH. Hymenophoral trama composed of subparallel hyphae 5-8 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis an entangled trichodermium of erect hyphae 12-19 μm in diameter, branched, yellowish-white to hyaline in 5% KOH, yellow brown to dark brown in Melzer’s reagent, terminal cells 20-50 × 6-10 μm, cylindrical, clavate or nearly fusoid. Stipitipellis a tangled layer of repent to suberect branching hyphae 7-10 μm in diam., hyaline in 5% KOH, with terminal cells 22-30 × 7-18 μm. Caulocystidia 43-58 × 12-18 μm, numerous, in clusters, clavate, fusoid or fusoid ventricose, mostly clavate, swollen at apex and usually contain yellow to yellowish-brown substance at an early stage in 5% KOH. Clamp connections absent in all tissues.

Ecology and distribution.

Solitary or scattered on ground with humus and debris under Fagaceae trees, mixed with other broadleaf trees, alt. 200-400 m; June to September; currently only known from southern China.

Additional specimens examined.

China, Hainan Province, Changjiang County, Bawangling National Forest Park, 7 July 2013, M. Zhang (ZhangM131).

Notes.

Aureoboletus griseorufescens is somewhat similar to the recently reported species A. venustus from southern China; however, the latter taxon differs in having relatively larger (pileus up to 8 cm) and more viscous basidiomata, a reddish-orange pileus and broader basidiospores 7.5-10.5 × 5-6 μm ( Li et al. 2016). In addition, A. griseorufescens formed a separate species level branch at the base of the phylogenetic tree ( Fig. 1 ), indicating that it is in an independent phylogenetic position.

Figures

Figure 1. Maximum likelihood tree from a RAXML search using the GTRGAMMA model, illustrating the phylogeny of Aureoboletus and related taxa in Boletales, based on a multilocus (nrLSU, tef 1 - a, rpb 1 and rpb 2) dataset. Phylloporus imbricatus N. K. Zeng, Zhu L. Yang & L. P. Tang and Xerocomus subtomentosus (L.) Quel. are chosen as outgroups. The lineages with new species and new combination are bold in the tree. Branches are labelled with maximum likelihood bootstrap higher than 70 % and Bayesian posterior probabilities more than 0.95.

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