34
Comparison
of
the
frequency
and
distribution
of
chiasmata
in
diploid
and
tetraploid
forms
of
Lycopersicon
pimpinellifolium
Strelnikova
S
.
R
.
Department
of
Genetics,
Moscow
K
.
A
.
Timiryazev
Agricultural
Academy,
Moscow,
127550,
Russia
The
number
of
chromosomes
(to
geneticists,
units
of
linkage)
is
the
important
value
determining,
among
others,
the
extent
of
free
combination
of
genetical
factors
in
meiosis
.
It
is
accepted
that
polyploidy
leads
to
an
increase
of
the
genetical
variability
in
a
population
(Zhuchenko,
1988)
.
Autopolyploids
are
featured
by
the
presence
in
their
genome
of
two
or
more
identical
sets
of
homological
pairs
of
chromosomes
.
A
number
of
authors
have
reported
that
at
the
stage
of
autotetraploidy,
compared
to
the
diploid
organisms
the
chiasmata
frequency
does
not
increase
twofold
constantly,
but
multiplies
by
a
coefficient
dependent
on
the
species
(MacCollum,
1958;
Wallace,
Callow
1995)
.
For
the
purpose
of
comparison
we
took
the
species
Lycopersicon
pimpinellifolium
2n=24
and
its
autotetraploid
2n=48
.
The
investigation
of
the
frequency
and
distribution
of
chiasmata
was
carried
out
with
the
use
of
temporary
squashed
preparations
obtained
from
anthers
where
the
pollen
mother
cells
was
at
the
stage
of
diakinesis
.
The
material
was
dyed
with
acetocarmine
.
The
temporary
squashed
preparations
were
prepared
in
the
saturated
solution
of
chloralhydrate
.
The
observations
and
microphotography
were
carried
out
with
use
of
microscope
with
phase
contrast
"Axiophot"
(Opton)
at
the
magnification
of:
objective
lens
100x,
eye
-
piece
lens
2
.
5x
.
The
cells
with
non
-
damaged
cellular
cell
walls
and
all
chromosomes
clearly
visible
were
photographed
for
purpose
of
detailed
analysis
of
chiasmata
frequency
and
distribution
.
In
the
diploid
L
.
pimpinellifolium
,
one
can
observe
a
strict
bivalentical
association
in
diakinesis,
i
.
e
.
,
the
entire
absence
of
poly
-
and
univalents
.
In
the
instance
of
the
autotetraploid
analogue,
in
the
contrary,
during
the
analysis
of
the
pollen
mother
cells
at
the
stage
of
diakinesis
were
observed
not
only
bivalents,
but
also
univalents
and
various
types
of
quadrivalents
(Table1)
.
Table
1
.
Frequency
of
occurrence
of
violations
in
diakinesis
in
48
-
chromosomes
species
Cases
encountered
Number
of
cells
%
All
bivalents
17
40
.
4
22
bivalents
and
1
closed
quadrivalent
8
19
.
0
22
bivalents
and
1
open
chain
quadrivalent
6
14
.
3
20
bivalents
and
2
closed
quadrivalents
3
7
.
1
20
bivalents,
1closed
quadrivalent
and
1
open
chain
quadrivalent
6
14
.
3
21
bivalents,
2
univalents
and
1open
chain
quadrivalent
1
2
.
38
19
bivalents,
2
univalents
and
2
closed
quadrivalents
1
2
.
38
Total
42
100
It
was
found
that
7%
of
chromosomes
are
joined
in
quadrivalents
.
Compared
to
the
tetraploids
of
the
other
species,
it
is
a
very
small
value
.
Furthermore,
40%
of
the
analyzed
cells
contain
only
bivalents
.
Even
at
the
stage
of
tetraploid
the
bivalentical
association
holds
.
