Diversity of Cenococcum geophilum isolates from serpentine and non-serpentine soils

Serpentine soils are characterized by a disproportionate level of Mg in rel ation to Ca and often contain phytotoxic levels of available Ni. Both of th ese factors may represent stresses to plants and fungi colonizing these soi ls. Ectomycorrhizal fungi play important roles in tree biology, and ecotypi c adaptation in these fungi may be critical to the success of trees on serp entine soils. A collection of Cenococcum geophilum isolates was obtained fr om serpentine and non-serpentine soils by trapping isolates on the roots of Virginia pine (Pines virginiana) seedlings. Restriction fragment length po lymorphism (RFLP) analysis of the internal transcribed spacer region of rib osomal repeat exhibited certain common fragments among isolates and other f ragments that varied in length. Additional polymorphic markers were obtaine d from PCR-amplified beta -tubulin gene fragments. UPGMA analysis of the RF LP data indicated that, with one possible exception, the serpentine isolate s of C. geophilum are genetically more similar to each other than they are to the isolates from local or distant non-serpentine sites. AFLP analyses, sampling a greater number of loci across the genome, provided an even more distinct separation of the serpentine isolates from non-serpentine isolates . All serpentine isolates lacked a group I intron frequently found within t he 18S ribosomal RNA gene in isolates of this species. The genetic divergen ce between serpentine and non-serpentine isolates may reflect adaptation to serpentine soil factors.