The Cedrus-associated truffle Trappeindia himalayensis is a morphologically unique and phylogenetically divergent species of Rhizopogon

Abstract

ABSTRACTIn the northwestern Himalayan mountains of India, the hypogeous sequestrate fungus Trappeindia himalayensis is harvested from forests dominated by the ectomycorrhizal tree Cedrus deodara (Himalayan cedar). This truffle has basidiospores that are ornamented with raised reticulation. The original description of Trappeindia himalayensis suggested that the gleba of this species is similar to young specimens of Scleroderma (Boletales), whereas its basidiospores are ornamented with raised reticulation, suggesting a morphological affinity to Leucogaster (Russulales) or Strobilomyces (Boletales). Given this systematic ambiguity, we have generated DNA sequence data from type material and other herbarium specimens and present the first molecular phylogenetic analysis of this unusual Cedrus-associated truffle. Despite the irregular ornamented basidiospore morphology, T. himalayensis is resolved within the genus Rhizopogon (Suillineae, Boletales) and represents a unique lineage that has not been previously detected. All known Rhizopogon species possess an ectomycorrhizal trophic mode, and because of its placement in this lineage, it is likely that Trappeindia himalayensis is an ectomycorrhizal partner of Cedrus deodara. This study highlights the importance of generating sequence data from herbarium specimens in order to identify fungal biodiversity and clarify the systematic relationships of poorly documented fungi.