Rubroboletus esculentus Kuan Zhao, Hui M. Shao & Zhu L. Yang, 2017

Zhao, Kuan & Shao, Hui M., 2017, A new edible bolete, Rubroboletus esculentus, from southwestern China, Phytotaxa 303 (3), pp. 243-252 : 246-248

Rubroboletus esculentus Kuan Zhao, Hui M. Shao & Zhu L. Yang , sp. nov.

Mycobank: — MB 820256

Etymology: — “ esculentus ” refers to its edibility.

Holotype: — CHINA. Sichuan Province: Xiaojin County, Wori Town, Bandong Mountains , on the ground in a forest of Quercus semecarpifolia , 3350 m, 16 August 2016, Kuan Zhao 893 ( HKAS 96782 , holotype!).

Description: —Pileus 7–12 cm in diameter, hemispherical to convex; surface vivid red (10A7–8), blood red (10D7–8) to dark red (11C7–8), strongly viscid when wet and shiny when dry, becoming darker when bruised; context 2–2.5(3) cm thick, bright yellow (2A5–7) to golden yellow (3A6–7), immediately becoming blue when injured. Hymenophore depressed around stipe, surface blood red (10D7–8) to brownish red (9C7–9D7) when mature, rapidly bluing when bruised; pores angular, 2–3/mm; tubes up to 1.5–2 cm in depth, yellow (3B7–8) to olivaceous green (30C5–7), becoming dark blue very quickly when injured. Stipe 9–12(15) × 2–4(5) cm, robust, often bulbous at the base, background yellow (4A7–8), covered with an orange-red to brownish yellow granulose, but irregularly cracked with age and the yellow background exposed, bruising blue when injured; mycelium at the base of the stipe white; context bright yellow to golden yellow, but rusty red at the very bottom, turning blue quickly when injured. Odor fragrant and taste mild.

Basidiospores [100/5/3] 12–15 (16) × 5–6 (6.5) μm [Q = (2.17) 2.25–2.73 (2.80), Q m = 2.46 ± 0.18], ovoid-ellipsoid, nearly colorless in KOH and yellowish brown in Melzer’s reagent. Basidia 36–55 × 10–14 μm, clavate, 4- spored, sometimes 2-spored. Cheilocystidia 50–68 × 6–10 μm, ventricose-subfusiform, thin-walled, colorless in KOH. Pleurocystidia 56–82 (105) × 7–10 μm, similar with cheilocystidia in shape. Pileipellis an interwoven trichodermium ca. 150–200 μm thick, embedded in a gelatinized matrix, filamentous hyphae 3–5 μm in diameter. Stipitipellis ca. 120 μm thick, composed of 3–4 μm filamentous cells, with clavate terminal cells 30–50 × 10–14 μm. Stipe trama composed of vertically and densely arranged hyphae 2–3 μm. Clamp connections absent in all tissues. Amyloid reaction negative.

Habitat and distribution: — Solitary in a forest of Quercus semecarpifolia . Currently only known from Sichuan and Yunnan Province, southwestern China.

Other materials examined: — CHINA. Sichuan Province, Aba Tibetan and Qiang Autonomous Prefecture , Xiaojin County, on the ground in a forest of Quercus semecarpifolia , 3350 m, 16 August 2016, H. M. Shao-F1 ( HKAS 96783 ) ; Dujiangyan City , collected from a wild mushroom market, 25 July 2016, H. M. Shao-F2 ( HKAS 96784 ) ; Yunnan Province, Lijiang City, Dadong Village , in a forest of Quercus semecarpifolia , 18 August 2010, B. Feng 898 ( HKAS 68679 ) .

Notes: — Rubroboletus esculentus is characterized by its vivid red pileus which is very viscid when wet, blood red to brownish red hymenophore surface and fragrant smell. In the combined phylogenetic analyses, it is closely related to R. legaliae . However, the European species differs from R. esculentus by its grey to greyish brown pileus with pink tint at the cap margin and an acid taste. Morphologically, this species is similar to another Chinese species R. latisporus as they both have a vivid red and gelatinized pileus. However, the surface of the hymenophore of R. latisporus is orange-red to yellow when mature, while that of R. esculentus is blood red to brownish red; in addition, the spores of the former are ovoid-ellipsoid, without a conspicuous suprahilar depression, while that of the latter are boletoid, with an inconspicuous suprahilar depression. Rubroboletus esculentus was marked as “ Rubroboletus sp. HKAS 68679” in Fig. 1 of Wu et al. 2016a.

Figures

FIGURE 1. Maximum-Likelihood phylogenetic tree generated from ITS sequences. BS support values>50% for ML and PPs>0.95 for BI are indicated along branches (BS/PP).