The PCR technique based upon randomly amplified polymorphic DNA
(RAPD) markers using 10-mer oligonucleotide primers was
used to investigate the phylogenetic relationships among 33 isolates of
Heterobasidion annosum belonging to the intersterility groups
F and S. The F isolates originated from Italy, the S isolates from the
Italian Alps, northern Europe and North America. The presence
or absence of some bands was shown to be population-specific. The North
American S group and the European S group differed
significantly from each other, but within the latter group there were no
significant differences between the Italian S and the northern
European S populations, with as much similarity within these populations
as between them. More DNA polymorphisms appeared
within European F and S groups than in the North American S group. The
North American S group appeared to be more closely
related to the European S group than to the F group. The isolates of the
Italian F population seemed to be most closely related to
the Italian S isolates and then, in decreasing order, to the northern
European S and North American S isolates. The order of genetic
similarity was inversely correlated with the mating frequency
in vitro obtained in an earlier study.