Psiloboletinus is an independent genus sister to Suillus

The genus Psiloboletinus was proposed by Rolf Singer in 1945 based on Phylloporus lariceti, a species that associates with Larix in the Altai Mountains of central and eastern Asia. However, this classification has been controversial due to the morphological similarity to known genera Boletinus and Fuscoboletinus. Because of the lack of fresh material to study, the phylogenetic position of Psiloboletinus has remained unknown since its publication. However, the recently described species Suillus foetidus reported from northeast China allows this issue to be reexamined and resolved. Through morphological observations and comparison, we find that S. foetidus is a heterotypic synonym of Ps. lariceti. Furthermore, Psiloboletinus should be retained as an independent genus sister to Suillus based on molecular phylogenetic evidence and morphological features.