Caloboletus xiangtoushanensis Ming Zhang, T.H. Li & X.J. Zhong, 2017

Zhang, Ming, Li, Tai Hui, Gelardi, Matteo, Song, Bin & Zhong, Xiang Jing, 2017, A new species and a new combination of Caloboletus from China, Phytotaxa 309 (2), pp. 118-126 : 119-121

Caloboletus xiangtoushanensis Ming Zhang, T.H. Li & X.J. Zhong , sp. nov.

Mycobank: MB 820363

Etymology: The epithet xiangtoushanensis refers to the type locality Xiangtoushan.

Type:— CHINA, Guangdong Province, Huizhou County, Xiangtoushan National Nature Reserve, 23°18′ N, 114°23′ E, 500 m, 7 July 2015, Hao Huang & Ting Li (GDGM 44725, holotype!).

Macroscopic characters:—Basidiomes small to medium-sized. Pileus 4–9 cm in diam, subhemispherical to convex or nearly plane; margin usually slightly inrolled, especially when young; surface dry, covered with tomentose or with short fibrils to tomentose squamules, often slightly areolate or cracking from margin to disc, dull red to brownish orange at first (8C3–5C3), gradually fading to greyish yellow to pallid yellow (4C3–2C3) when mature, often with greyish ting. Context 1–1.5 cm thick at center of pileus, white to yellowish (2A2–4A2) with a faint pinkish ting, pink to purplish pink (12A4–14A4) beneath the pileipellis, staining light blue quickly when exposed, more obviously near hymenophore and inconspicuously under pileipellis. Hymenophore 5–8 mm deep, depressed around stipe, yellow, greyish yellow to olive yellow (2B8–3B8, 2C8–3C8) when mature, bluing quickly when injured; pores angular, 2–3 per mm, deep orange to reddish orange when young, greenish yellow to olive yellow (2B8–3B8, 2C8–3C8) when mature, staining dark blue quickly when injured. Stipe 3–8 × 1–1.5 cm, central, subcylindrical or clavate, solid, equal to slightly enlarged downwards, yellowish white to pale yellow (2A2–3A2, 2A3–3A3), covered with yellowish red to vivid red (8A8–9A8) reticulation or longitudinal striated ornamentation at first, then fading to greyish yellow with age upwards from the base but often retaining some reddish hues at apex in mature specimens, unchanging to very weakly staining blue when injured; basal mycelium white to yellowish white (1A2), context brown to reddish brown (6D8–9D8), becoming bluish slowly when injured. Odour indistinct. Taste bitter.

Microscopic characters:—Basidiospores [60/2/2] 9–13(–13.5) × 4–5 μm, [Q=(2.22–)2.4–2.75(–2.89), Qm =2.54 ±0.15], oblong to subfusoid, barely inequilateral in profile, smooth, yellowish to pale yellowish-brown in 5% KOH and yellowish brown to dark brown in Melzer’s reagent, thin-walled. Basidia 25–33× 7–10 μm, clavate, hyaline in 5% KOH and yellowish to yellowish brown in Melzer’s reagent, 4-spored, without basal clamps, sterigmata 2.5–4 μm long. Cheilocystidia abundant, 28–50 × 7–12 μm, narrowly fusiform, thin-walled, smooth, yellowish white to hyaline in 5 % KOH, inamyloid. Pleurocystidia similar to cheilocystidia in size and shape. Hymenophoral trama subparallel to somewhat bilateral, yellowish to hyaline in 5 % KOH, yellowish to yellowish brown in Melzer’s reagent, composed of branching hyphae 5–10 μm wide, yellowish to hyaline in 5 % KOH, yellowish to yellowish brown in Melzer’s reagent, thin-walled. Pileipellis made up of loosely entangled hyphae; pileipellis hyphae occasionally branched, smooth, thin-walled, hyaline, sometimes outer surface covered with brown granular pigments not dissolving in KOH. Stipitipellis composed of broadly clavate inflated cells, yellowish white to hyaline in 5 % KOH. Stipe trama composed of longitudinally arranged cylindrical cells 4–12 μm wide, thin-walled, branched, smooth, yellowish white to hyaline in 5 % KOH. Clamp connections absent.

Habit, habitat and distribution:—Solitary to scattered on soil in broadleaf forests mainly associated with Cyclobalanopsis spp. and Castanopsis spp. ( Fagaceae ). Currently known from Guangdong and Zhejiang Provinces, China.

Additional specimens examined:— CHINA, Guangdong Province: Huizhou City, Xiangtoushan National Nature Reserve, 23°18′ N, 114°23′ E, alt. 560 m, 7 July 2015, Hao Huang and Ting Li (GDGM 44833). Zhejiang Province: Wuyi County, 28°40′ N, 119°30′ E, alt. 600 m, 22 August 2015, Chuan-Hua Li (GDGM 45160).

Notes: Caloboletus xiangtoushanensis is characterized by its medium-sized basidiomes with a brownish orange to greyish yellow pileus, light yellow to light orange stipe covered with obvious reticulation, greyish yellow to olive yellow hymenophore that quickly stains blue when bruised and a bitter taste. According to the combination of the aforementioned morphological characters, this species can easily be distinguished from other taxa of Caloboletus . This new species is morphologically and phylogenetically closely related to Boletus taienus (= “ Caloboletus taienus ” described hereafter). However, the latter can be easily distinguished by its olive yellow to brownish yellow pileus, deep red to ruby pores and smaller spores 8–10.5 (–11) × (3.5–) 4–4.5(–5) μm ( Chiu 1948; this study). Morphologically, C. xiangtoushanensis is somewhat similar to C. panniformis (Taneyama & Har. Takah.) Vizzini originally reported from Japan. However, C. panniformis is different in the brown to brownish orange pileus, red stipe and much larger spores (11.3–) 13.6–15.2 (–16.4) × (4.6–) 5.4–6.0 (–6.5) μm ( Takahashi et al. 2013). Finaly, Boletus gansuensis Q.B. Wang, T.H. Li & Y.J. Yao , originally described from Gansu Province of China, exhibits some macromorphological similarities with C. xiangtoushanensis especially in the colours of the basidiomes and context discolouration, having a pale red to pastel red pileus, pinkish red pores, and a bluing context when injured. However, B. gansuensis can be easily distinguished by its larger basidiospores 12–15.5 × 6–7 μm ( Wang et al. 2003).