Identity and spatial distribution of the fungal symbiont of Sarcodes sanguinea.

BIDARTONDO, MARTIN I.², ANNETTE M. KRETZER¹, LISA C. GRUBISHA¹, TIMOTHY M. SZARO² & THOMAS D. BRUNS².

¹Oregon State University, Department of Botany and Plant Pathology, Corvallis, OR 97331-2902, USA; ²University of California at Berkeley, Department of Plant and Microbial Biology, Berkeley, CA 94720-3102, USA.

The snow plant (Sarcodes sanguinea, Monotropoideae) is an achlorophyllous plant that obtains all its carbon from fir (Abies) hosts through mycorrhizal links. We have sampled the root balls of 64 plants in two areas of the Sierra Nevada of California and used molecular techniques to identify their fungal symbionts. In both areas, approx. 180 km apart , S. sanguinea seems to associate exclusively with Rhizopogon ellenae, a hypogeous ectomycorrhizal fungus in the Boletales (Basidiomycota). In order to assess the abundance of R. ellenae in mycorrhizal communities where S. sanguinea is present, we sampled fir mycorrhizae at 5 m, 1 m, 0.5 m, 0.1 m, and 0 m from S. sanguinea in a pure red fir stand (Abies magnifica). Fir roots that intermingle with the rootballs of S. sanguinea are infected predominantly with R. ellenae, while the same fungus is much less common just 10 cm away from S. sanguinea, and becomes rare at 1 m. This suggests that most carbon transfer from Abies to S. sanguinea via R. ellenae occurs over short distances. Our results show that S. sanguinea occupies small dense patches of R. ellenae within a complex mycorrhizal community. A molecular characterization of the fir mycorrhizal community on our research site is under way.