ITS primers with enhanced specificity for basidiomycetes - application to the identification of mycorrhizae and rusts
M. Gardes and T. D. Bruns
Department of Plant Pathology, University of California, Berkeley
We have designed two taxon-selective primers for the internal
transcribed spacer (ITS) region in the nuclear ribosomal repeat unit.
These primers, ITS1-F and ITS4-B, were intended to be specific to fungi
and basidiomycetes, respectively. We have tested the specificity of these
primers against 13 species of ascomycetes, 14 of basidiomycetes, and 15
of plants. Our results showed that ITS4-B, when paired with either a
'universal' primer ITS1 or the fungal-specific primer ITS1-F, efficiently
amplified DNA from all basidiomycetes and discriminated against
ascomycete DNAs. The results with plants were not as clearcut. The
ITS1-F/ITS4-B primer pair produced a small amount of PCR product
for certain plant species, but the quantity was in most cases less than
that produced by the 'universal' ITS primers. However, under
conditions where both plant and fungal DNAs were present, the fungal
DNA was amplified to the apparent exclusion of plant DNA. ITS1-
F/ITS4-B preferential amplification was shown to be particularly useful
for detection and analysis of the basidiomycete component in
ectomycorrhizae and in rust-infected tissues. These primers can be used
to study the structure of ectomycorrhizal communities or the
distribution of rusts on alternate hosts.
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