Microsatellite markers reveal the below ground distribution of genets in two species of Rhizopogon forming tuberculate ectomycorrhizas on Douglas fir

We have developed microsatellite markers for two sister species of Rhizopogon, R. vesiculosus and R. vinicolor (Boletales, Basidiomycota), and used selected markers to investigate genet size and distribution from ectomycorrhizal samples. Both species form ectomycorrhizas with tuberculate morphology on Douglas-fir (Pseudotsuga menziesii). Tuberculate ectomycorrhizas were sampled and mapped in two 10 x 10 m core plots located at Mary's Peak in the Oregon Coast Range and at Mill Creek in the Oregon Cascade Mountains, USA; additional samples were obtained from a larger area surrounding the Mary's Peak core plot. Gene diversities at the newly described microsatellite loci ranged from 0.00 to 0.68 in R. vesiculosus, and from 0.00 to 0.43 in R. vinicolor. Both taxa appeared to be in Hardy-Weinberg and linkage equilibrium. The largest distance observed between tuberculate ectomycorrhizas of the same genet was 13.4 m for R. vesiculosus, but only 2 m for R. vinicolor. This is to our knowledge the first study to differentiate fungal genets from ectomycorrhizas with great confidence using multiple codominant markers.