Mitochondrial and nuclear genes have different inheritance, thus
studies of fungal populations should use both
mitochondrial and nuclear markers. Using nuclear markers, the S238N strain
of the ectomycorrhizal basidiomycete
Laccaria bicolor ((Maire) Orton) has been previously shown to
persist for at least 10 yr after outplanting in a
plantation of Douglas fir (Pseudotsuga menziesii (Mir.) Franco)
inoculated with this strain. In the present study,
we have sampled 539 sporophores of Laccaria spp. from this plantation,
some of which had the S238N nuclear
genotype, to study mitochondrial DNA polymorphism and persistence of the
inoculated S238N mitochondrial
genome. Length polymorphism in fragments of the large subunit of mitochondrial
ribosomal DNA (LrDNA)
allowed distinction of the haplotypes present in the plantation at the
species level. In addition, heteroduplex
analysis and sequencing revealed intraspecific polymorphism of LrDNA among
the L. bicolor sporophores and
enabled specific identification of S238N LrDNA. This haplotype was only
retained in sporophores carrying the
S238N nuclear genome, confirming the survival of this introduced strain
in a natural population.