VARIATION IN THE RIBOSOMAL DNA INTERNAL TRANSCRIBED SPACER OF A DIVERSE COLLECTION OF ECTOMYCORRHIZAL FUNGI

Amplification of the internal transcribed spacer (ITS) of ribosomal RN A genes using PCR and subsequent RFLP analysis offers promise for impr oved species-level identification of ectomycorrhizal fungi. Intragener ic homogeneity and intraspecific heterogeneity of these characters are , however, frequent. A diverse group of ectomycorrhizal fungi with wor ldwide distribution was characterized by ITS-RFLP analysis. DNA of 64 identified and five unknown ectomycorrhizal fungi was extracted and th eir ITS regions were selectively amplified with ITS1-F and ITS4 riboso mal RNA gene primers. Each PCR product was digested with seven restric tion enzymes. The resulting restriction fragments were compared by dis tance matrix analysis. Restriction enzyme analysis of amplified fragme nts was sufficient for distinguishing all but two closely related spec ies. Intraspecific variation was observed in Cenococcum geophilum and Pisolithus arhizus, providing further evidence that these taxa represe nt species complexes.