Low genetic differentiation among Italian populations of Populus tremula L. (Salicaceae) estimated using chloroplast PCR/RFLP and microsatellite markers

Chloroplast (cp) DNA polymorphism was analysed in ten Italian populations of Populus tremula L. byPCR-
RFLP
and microsatellites (SSR) chloroplast
markers. Amplified
fragments
were
digested
by
restriction
endonucleases
and
the resulting restriction fragments
were
separated
by
gel electrophoresis. Three
cpDNA
amplification products showed polymorphism
after
digestion.
By
analysing
this
polymorphism
we
identified
six
haplotypes.
Five universal
pairs of primers were
used
for
the amplification
of
specific
cpDNA
microsatellite
regions,
which
are supposed
to
contain
mononucleotide
stretches
(A/T).
Two microsatellite
loci
showed
polymorphism,
resulting
in
a
total of six
haplotypes. Both
PCR-RFLP
and
SSR
chloroplast markers
revealed
very
low genetic differentiation among populations,
with
G,,
=
0.22
and
N,,
=
0.24
(PCR-RFLP),
and
G,,
=
0.07
and
N,,=
0.07
(SSR),
resulting about
4-10
times lower than
the
mean
G,,
value
estimated
in
broad-leaved forest
species for
maternally
inherited markers. This could
be
mainly
explained
by
the
high
efficiency
of
P,
trernula
seed wind dispersal over
long
distances, determining little geographic structure
of
the
genetic diversity.