Diversity of Cenococcum geophilum Isolates from Serpentine and Non-Serpentine Soils.
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AbstractSerpentine soils are characterized by a disproportionate level of Mg in relation to Ca and often contain phytotoxic levels of available Ni. Both of these factors may represent stresses to plants and fungi colonizing these soils. Ectomycorrhizal fungi play important roles in tree biology, and ecotypic adaptation in these fungi may be critical to the success of trees on serpentine soils. A collection of Cenococcum geophilum isolates was obtained from serpentine and non-serpentine soils by trapping isolates on the roots of Virginia pine (Pinus virginiana) seedlings. Restriction fragment length polymorphism (RFLP) analysis of the internal transcribed spacer region of ribosomal repeat exhibited certain common fragments among isolates and other fragments that varied in length. Additional polymorphic markers were obtained from PCR-amplified β-tubulin gene fragments. UPGMA analysis of the RFLP data indicated that, with one possible exception, the serpentine isolates 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 the 18S ribosomal RNA gene in isolates of this species. The genetic divergence between serpentine and non-serpentine isolates may reflect adaptation to serpentine soil factors. AccessAvailable at Jstor.org |