Morphological and molecular evidence of specificity between Allotropa virgata and Tricholoma magnivelare.

LEFEVRE, CHARLES K.¹, CAROL M. CARTER², AND RANDY MOLINA³.

¹Department of Forest Science, Oregon State University, Corvallis, Oregon, USA. ²Department of Biology, Portland State University, Portland, Oregon, USA. ³USDA Forest Service, Pacific Northwest Research Station, Corvallis, Oregon, USA.

Many achlorophyllous plants depend on fungi to supply the carbohydrates that plants normally gain through photosynthesis. Several species exhibit narrow or exclusive specificity for particular species of ectomycorrhizal fungi. Allotropa virgata, a member of the Monotropoideae, is consistently observed near sporocarps of Tricholoma magnivelare, the American matsutake. To test whether A. virgata associates with T. magnivelare, we analyzed mycorrhizae in 37 soil samples collected throughout most of A. virgata 's geographic range. All soil samples exhibited the bleached, dry and powdery condition characteristic of T. magnivelare mats as well as the unique aroma of matsutake mushrooms. Only one morphotype of A. virgata mycorrhizae was observed based on color, texture, branching and mantle characteristics; and the fungal ITS-RFLP patterns from A. virgata root tips match those from T. magnivelare sporocarps. This mycorrhizal association is among the most specific ever observed for a plant and it provides a precise indicator for colonies of the commercially important American matsutake mushroom.