Retiboletus cyanescens Yan C. Li & Zhu L.

Li, Jin, Wang, Zhen, Liu, En-De, Yang, Zhu L. & Li, Yan-Chun, 2022, Morphological and molecular data reveal Retiboletus cyanescens sp. nov. and the new subgenus Nigroretiboletorum (Boletaceae), Phytotaxa 572 (3), pp. 232-242 : 237-238

Retiboletus cyanescens Yan C. Li & Zhu L. Yang, sp. nov. Figures 2 a–d , 3

MycoBank: 845728

Etymology: cyanescens referring to the context in stipe staining indistinct blue when injured.

Type: China. Yunnan Province: Anning County, alt. 2050 m, 15 July 2021, Y. C. Li 2967 (holotype: KUN-HKAS 122939 ) .

Diagnosis: Retiboletus cyanescens can be distinguished from the other species in Retiboletus by the combination of the gray to blackish pileus, the white, grayish white to yellowish gray stipe which is yellowish to brownish yellow downwards, the entirely reticulate stipe surface, the cream basal mycelium, the bluish discoloration in the middle part of the stipe when injured, the palisadoderm pileipellis, and the subtropical to temperate distribution.

Description: Basidiomata small to medium-sized. Pileus 3–10 cm in diameter, subhemispherical to applanate, surface dry, finely subtomentose, dark brown (5F8), brown (5E8), black (4F2), or brown-gray (4C2) in the center and brownish (5B4-5) or grayish (4B2) towards margin. Context whitish (4A1) to cream (4A3), without color change when injured. Hymenophore adnate to slightly decurrent, or sometimes depressed around apex of stipe when mature; surface initially whitish (4A1) and then dirty white or grayish (4B1); pores angular to roundish, 0.5–1.5 mm wide; tubes up to 4–6 mm in length, concolorous or a little paler than hymenophoral surface, without color change when injured or sometimes with rust brownish spots when touched. Stipe 3–7 × 0.3–0.7 cm, clavate to subcylindrical, flexuous, solid; surface grayish white (4B2) to pale range (5A3), covered with blackish to dark brown reticulum, without color change when hurt; context white (4A1) to cream (4A3) at upper part and cream to yellowish (4A2) downwards, staining indistinct blue in the middle part when injured; basal mycelium cream (4A3) without color change when injured. Taste and odor mild.

Basidia 28–40 × 9–12 μm, clavate, thin-walled, 4-spored, hyaline to yellowish in KOH. Basidiospores [100/5/5] (9.5) 10–13 (14.5) × 4–5 μm, [Q = (2.11) 2.30–3.13 (3.25), Q m = 2.60 ± 0.18], sub- fusiform and inequilateral with slightly suprahilar depression in side view, elongate fusoid or narrowly oblong in ventral view, slightly thick-walled (up to 0.5 μm), brownish or pale brown in KOH, olive-brown to brown in Melzer’s reagent, smooth. Hymenophoral trama boletoid; hyphae cylindrical, 3–14 μm wide, hyaline to yellowish in KOH, yellowish to yellow in Melzer’s reagent. Cheilocystidia 27–37 × 5–7 μm, fusiform or subfusiform, thin-walled, brownish to pale yellow-brown in KOH; surface without encrustations. Pleurocystidia relatively big, 44–65 × 6–10 μm, fusiform or subfusiform, thin- to slightly thickwalled (up to 0.5 μm), concolorous with cheilocystidia; surface without encrustations. Caulocystidia forming the reticulum over the stipe surface, morphologically similar to cheilo- and pleurocystidia. Pileipellis a trichoderm about 150 μm thick, composed of more or less vertically arranged to slightly interwoven, brown to dark brown hyphae, 6–16 μm wide; terminal cells 21–38 × 6–16 μm, narrowly clavate to subcylindrical or subfusiform, sometimes narrowly mucronate, rostrate, thin-walled, yellowish brown to brownish in KOH, yellow-brown to brown in Melzer’s reagent. Pileal trama composed of thin-walled hyphae, 3–9 μm wide, hyaline to yellowish in KOH, yellowish to yellow in Melzer’s reagent. Clamp connections absent in all tissues.

Habitat, ecology and distribution: Solitary on the ground in subtropical to temperate forests dominated by plants of the family Fagaceae ; currently known from southwestern China.

Additional specimens examined: China. Yunnan Province: Kunming City, Anning County, alt. 2050 m, 15 July 2021, Y.C. Li 2975 and Y.C. Li 2980 ( KUN-HKAS 122940 and KUN-HKAS 122941 , respectively) ; Lijiang County, Wenbi Mountain , alt. 2400 m, 14 July 2019, C. Huang 013 ( KUN-HKAS 106692 ) ; Kunming City, Kunming Institute of Botany , alt. 1980 m, Z.L. Yang 5698 ( KUN-HKAS 79637 ) .

Figures

FIGURE 2. Basidiomata of R. cyanescens. a–b. from KUN-HKAS 122939; c. from KUN-HKAS 106692; d. from KUN-HKAS 122940.

FIGURE 3. Microscopic features of R. cyanescens (KUN-HKAS 122939). a. Basidiospores; b. Basidia and pleurocystidium; c. Cheilocystidia; d. Pleurocystidia; e. Pileipellis; f. Reticulum on stipe. Scale bars: 10 μm.