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Clone size, fine-scale population structure, and phylogenetic species in the ectomycorrhizal false-truffle Rhizopogon vinicolor complex. A. M. Kretzer (1), R. Molina (2), L. C. Grubisha (3), and J. W. SPATAFORA (1). (1) Dept. of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA; (2) US Forest Service, PNW Research Station, Corvallis, OR, USA; (3) Dept. of Plant & Microbial Biology, University of California, Berkeley, CA, USA. Phytopathology 91:S116. Publication no. P-2001-0099-MSA.

A population genetic study was initiated to study population dynamics of the ectomycorrhizal false-truffle Rhizopogon vinicolor. R. vinicolor is host specific with Pseudotsuga menziesii and produces hypogeous sporocarps and nonforcibly discharged spores that are dispersed through small mammal mycophagy. It is the only false-truffle reported to produce tuberculate mycorrhizae, which consist of clusters of ectomycorrhizal root tips encased in a peridium. These tuberculate mycorrhizae are relatively easy to sample in nature and are more widely distributed than sporocarps. We developed numerous microsatellite markers to address several questions including clone size and distribution, fine scale population structure, and gene flow in the context of isolation by distance and barriers. Our initial results supported that clone size ranged from less than 5 m to approximately 15 m in diameter. More exhaustive sampling and analyses revealed that two sympatrically distributed Rhizopogon species produce tuberculate mycorrhizae. The latter results were corroborated by the lack of shared alleles across microsatellite loci, and through phylogenetic analysis of the ITS rDNA. We will also present preliminary data on fine-scale population structure at the water shed level and relative rates of inbreeding.