Hydnum species producing whitish basidiomata in Japan

• Hydnum minum sp. nov. is described based on morphological and phylogenetic analyses.
• Hydnum albomagnum is newly recorded in Japan.
• A key to the currently accepted Hydnum species based on morphological and phylogenetic data.

A new species of the genus Hydnum, H. minum, with whitish basidiomata, is described and illustrated from Japan based on morphological and phylogenetic analyses. This species is characterized by small basidiomata (1–2.5 cm in height), spinose hymenophores with small, conical to aciculate spines (0.5–1.7 mm in length, 150–250 μm in diameter), subclavate to suburniform basidia with 5–8 sterigmata, and subglobose to broadly ovoid basidiospores measuring 4.5–5.5 × 3–4.5 μm. In addition, H. albidum, H. albomagnum, newly recorded in Japan, and H. repandum var. album are analyzed using molecular tools. The four taxa were confirmed as each individual taxon by the molecular phylogenetic analysis using complete nuclear ribosomal internal transcribed spacer regions.