Retiboletus subg. Nigroretiboletorum Yan C. Li & Zhu L. Yang, 2022

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

Retiboletus subg. Nigroretiboletorum Yan C. Li & Zhu L. Yang , subg. nov.

MycoBank: 845727

Etymology: the epithet refers to species of this subgenus with gray, grayish-brown or black colored pileus.

Type: Retiboletus griseus ( Frost in Peck) Binder & Bresinsky , Feddes Repert 113(1–2): 37 (2002).

Diagnosis: Retiboletus subg. Nigroretiboletorum differs from R. subg. Retiboletus by its white, grayish white or pallid gray to cream context, unchanging or staining pale brown, brown, blackish brown, or ferrugineous when injured, and the white to grayish white or grayish pink to dark purple hymenophore, which is unchanging or staining pale brownish, brown, dark brown or ferrugineous when injured.

Description: Basidiomata small to medium-sized. Pileus subhemispherical to convex, sometimes applanate; surface dry, densely subtomentose, grayish brown, pale brown to blackish brown or grayish white to blackish; margin incurved; context white, grayish white or pallid gray to cream, unchanging or staining pale brown, brown, blackish brown, or ferrugineous when injured. Hymenophore poroid, adnate or slightly depressed around apex of stipe; pores angular to roundish, white to grayish white or grayish pink to dark purple, unchanging or staining brownish, brown, dark brown or ferrugineous when injured; tubes grayish white or gray-white when young, then gray, grayish yellow, or lilac, unchanging or staining pale brown, brown, or dark brown when injured. Stipe central, subcylindrical, solid, usually flexuous; surface dry, grayish white, gray to blackish, but with yellow to gray-yellow tinge downwards; surface often covered with concolorous or much darker reticulum, sometimes without indistinct reticulum; context white, cream to grayish on the upper part, but yellowish to cream downwards, unchanging or staining pale brown, brown, blackish brown, ferrugineous or indistinct blue when injured; annulus absent. Basal mycelium white or cream. Odor indistinct. Basidiospores smooth, subfusiform to ellipsoid. Cheilo- and pleurocystidia subfusiform or fusiform, abundant. Pileipellis a trichoderm composed of more or less vertically arranged, or sometimes slightly interwoven hyphae. Clamp connections absent in all tissues.

Ecology and distribution: Known from North and Central America and East Asia, associated with plants of the families Fagaceae and Pinaceae .

Currently known species: Retiboletus ater , R. brunneolus , R. fuscus , R. griseus , R. nigerrimus (R. Heim) Manfr. Binder & Bresinsky , R. nigrogriseus , R. pseudogriseus , R. sinogriseus , R. vinaceipes B. Ortiz, Lodge & T.J. Baroni , R. zhangfeii and the newly described species R. cyanescens .