Stable isotope evidence for the saprotropic status of the truffle Schenella pityophilus

Abstract

This research attempts to resolve the mode of nutrition, i.e., saptrtrophic or ectomycorrhizal, for Schenella pityophilus, a sequestrate hypogeous fungus. While a majority of truffles in both the Ascomycota and the Basidiomycota are ectomycorrhizal, S. pityophilus is in the Geastrales in which species are saprotrophic. Stable isotope ratios of C and N have been used to elucidate fungal trophic modes. Stable isotopic ratios of N and C from fruiting bodies of S. pityophilus were compared to those of Rhizopogon species collected from the same sites and known to be ectomycorrhizal. Fruiting bodies of S. pityophilus were depleted in δ 15 N and enriched in δ 13 C relative to Rhizopogon species. Stable isotope data support the conclusion that S. pityophilus is saprotrophic rather than mycorrhizal.