Interspecific and intraspecific variation in the internal
transcribed spacer (ITS) region of rDNA of ectomycorrhizal
fungi of 44 species in 17 genera were examined using the restriction
fragment length polymorphism (RFLP)
method. For each species, two to five herbarium vouchers (mainly
basidiocarps), collected throughout
Fennoscandia, were examined. The ITS region was amplified using the
polymerase chain reaction (PCR) and the
universal primers ITS1 and ITS4, and subjected to RFLP analysis with
three endonucleases. Intraspecific
polymorphisms in the ITS region were found in seven species (in nine
of the 132 herbarium vouchers).
Polymorphisms were due to length mutations, ranging from 5 to 15 bp in
four of the seven polymorphic species
and mutations in endonuclease restriction sites in six species, mostly
affecting only one endonuclease, but in two
species two endonucleases. Using a single endonuclease, a unique RFLP
pattern could be obtained for more than
half the investigated species. By combining different endonucleases,
34 (77%) of the species could be
distinguished from another. The remaining RFLP types occurred in one
genus. On the basis of the low intra- but
high interspecific variation in the ITS region, it is concluded that
most ectomycorrhizas formed by the 44
investigated species should be recognized by comparison with this
dataset, if the mycorrhizas are sampled from
a site located in Fennoscandia. However, in datasets from even
larger geographical areas encompassing a higher
degree of intraspecific variation in the ITS region, or when mycorrhizas
from several sites distant from each other
are compared, it might be necessary to include local reference species.