Tuber torulosum: A new truffle species decorated with moniliform cystidia from Japan.

We describe a new truffle species, Tuber torulosum, based on molecular and morphological analyses. This species forms a single globose ascospore per ascus, pale yellow in color, as do Japanese T. flavidosporum and Chinese T. turmericum and T. xanthomonosporum in the Japonicum clade of the Tuber phylogeny. However, it can be distinguished from them microscopically by its whitish tomentose mycelium that partially covers the ascoma surface and the mesh size of its spore ornamentation. Cystidia are moniliform and yellowish to reddish. Molecular phylogenetic analysis using the internal transcribed spacer and partial large subunit regions of ribosomal DNA also supports T. torulosum as a distinct species. On the basis of our results, we provide a key to species in the Japonicum clade.