Suillus subg. Boletinus (Kalchbr.) R. Zhang, X. F. Shi, G. M. Mueller & P. G. Liu, 2025

Shi, Xiaofei, Zhang, Shiru, Mueller, Gregory M., Liu, Peigui, Yu, Fuqiang & Senanayake, Indunil C., 2025, A subgeneric revision of the genus Suillus (Suillaceae, Boletales) and novel taxa from Eastern Asia based on morphology and multigene phylogenies, IMA Fungus 16, pp. e 144260-e 144260 : e144260-

Suillus subg. Boletinus (Kalchbr.) R. Zhang, X. F. Shi, G. M. Mueller & P. G. Liu comb. & stat. nov.

Basionym.

Boletinus Kalchbr. , Mathematische und naturwissenschaftliche Mitteilungen. Mathem. Természettud. Közlem. 5: 286 (1867).

Typification.

Suillus cavipes (Klotzsch) A. H. Sm. and Thiers , Monogr. North Amer. Species Suillus: 30 (1964)

Etymology.

The subgenus name is referred from a former genus name “ Boletinus ”.

Diagnosis.

This subgenus differs from all other subgenera of Suillus by the presence of clamp connections in the hyphae of sporophores, pileus usually red, bright pinkish or yellowish brown, spore print brown with olive yellow, vinaceous or purple tinge.

Morphology.

Basidiomata stipitate-pileate with tubular hymenophore. Pileus develops from hemispherical to convex or applanate, fibrillose or squamulose, dry, usually red, bright pinkish or yellowish brown when mature; context yellow, no color change when cut. Hymenophore boletinoid, pores wide and compound, radially arranged, sometimes decurrent. Stipe subcylindrical to cylindrical, generally hollows in maturity, some remain solid, no glandular dots; veil presents, generally forming a double and dry annulus. Spore print brown with olive yellow, vinaceous or purple tinge.

Basidiospores smooth, oblong and inequilateral, hyaline yellow in KOH. Basidia 4 - spored, clavate, hyaline yellow in KOH. Cystidia abundant, large, up to 100 μm, surrounded by brown amorphous materials or not. Pileipellis a trichoderm, thin-walled, often tangled. Clamps constantly present in the trama of sporophores and in basidial basal septum, except in one species.

Habitat.

Scattered to gregarious, ectomycorrizal with Larix .

Known species.

Suillus ampliporus , S. asiaticus , S. cavipes complex, S. ochraceoroseus , S. paluster , and probably S. foetidus (See Notes).

Notes.

Boletinus was delimitated by Singer (1986) as a genus was almost correct except for S. ochraceoroseus without clamps. Boletinus is better to be retained in the genus Suillus . The key feature to differentiate Boletinus from other Suillus subgenera is the presence of clamps, but this character is not without an exception and the evolutionary function of clamps is not clear. More than three potential new species are reported in subg. Boletinus . Suillus cavipes remains a species complex. Suillus ampliporus is a replaced name of North American S. cavipes based on the geographical distribution ( Nguyen et al. 2016). The geographical range of S. cavipes complex extends to northern China and is likely panboreal.