Two new species of Rhizopogon associated with Pinus pumila from Japan

•This is the first record of Rhizopogon species associated with five-leaved pine (subgenus Strobus) in Japan.•These new species are distantly related to other known species associated with two-leaved pines (subgenus Pinus).•These new species are placed at unique positions in Rhizopogon phylogeny.

Rhizopogon (Boletales) is an ectomycorrhizal fungal genus that forms symbiotic associations with Pinaceae trees, especially Pinus and Pseudotsuga, and produce hypogeous sporocarps. The taxonomy of Rhizopogon has been well-studied in Europe and North America, but little work has been conducted in Asia. In Japan, previous studies described several Rhizopogon species, each of which was associated with two-leaved pines (subgenus Pinus) or Pseudotsuga japonica. In the present study, we describe R. alpinus sp. nov. and R. nitidus sp. nov. associated with Pinus pumila (subgenus Strobus) distributed in alpine regions of Japan. These two new species are phylogenetically and morphologically distinct from other Rhizopogon species, especially those associated with the subgenus Pinus.