Dihaploid
production
as
a
result
of
interspecific
hybridization
in
genus
Lycopersicon
Vulkova
Z
.
1
,
Stoeva
-
Popova
P
.
2
*,
and
Atanassov
A
.
2
1
Institute
of
Genetics,
1113
Sofia,
Bulgaria
2
Institute
of
Genetic
Engineering,
2232
Kostinbrod
-
2,
Bulgaria
*
Department
of
Biology,
Winthrop
University,
Rock
Hill,
SC
L
.
peruvianum
is
reproductively
isolated
from
other
species
of
the
genus
Lycopersicon
(Rick
1963;
1979)
.
This
reproductive
isolation
barrier
can
be
easily
overcome
if
the
hybridization
is
carried
out
between
diploid
plants
of
L
.
peruvianum
and
colchicine
induced
autotetraploid
plants
from
another
Lycopersicon
species
(Vulkova
-
Achkova
and
Stoeva
1978)
.
As
a
result
sequidiploids
are
produced
that
are
highly
sterile
but
can
be
used
as
bridge
hybrids
for
the
introgression
of
genes
from
L
.
peruvianum
.
In
our
experiments
sesquidiploid
F1
hybrid
plants
produced
from
the
cross
between
L
.
hirsutum
typicum
(2n
48)
X
L
.
peruvianum
(2n
24)
were
used
.
Explants
from
in
vitro
propagated
sesquidiploid
F1
plants
were
cultivated
on
solid
MS
(Murashige
and
Skoog
1962)
medium
supplemented
with
30
g/l
sucrose,
2
mg/l
TDZ,
0
.
5
mg/l
IAA
and
1
mg/l
GA
.
After
20
-
25
days
on
this
induction
medium
callus
with
shoot
primordia
were
produced
on
the
cultivated
explants
.
The
formed
structures
were
transferred
for
further
development
on
MS
medium
with
30
g/l
sucrose
and
reduced
amounts
of
TDZ
–
0
.
5
mg/l,
IAA
–
0
.
1
mg/l,
and
GA
–
0
.
5
mg/l
.
On
this
medium
shoots
developed
.
The
regenerated
shoots
were
rooted
on
hormone
free
MS
medium
.
The
produced
R1
plants
were
transferred
to
soil
and
grown
in
pots
in
the
greenhouse
.
According
to
their
morphological
characteristics
the
regenerants
(R1)
were
classified
in
two
groups
.
The
first
group
comprised
of
10
plants
with
indistinguishable
L
.
peruvianum
phenotype
.
In
the
second
group
13
plants
with
intermediate
habitus
were
classified
.
The
meiotic
and
mitotic
divisions
as
well
as
pollen
stainability
were
studied
in
all
R1
plants
produced
.
To
study
mitosis,
root
tips
were
treated
with
a
-
brom
naphtalene
and
fixed
in
acetic
acid
and
96%
ethyl
alcohol
(1:3
w/w)
.
Schiff’s
reagent
was
used
to
stain
the
mitotic
chromosomes
in
squash
preparation
.
Meiosis
was
studied
in
squash
preparations
of
acetocarmine
(4%)
stained
anthers
.
Pollen
stainability
was
investigated
with
1%
acetocarmine
.
All
plants
from
the
first
group
had
24
chromosomes
.
It
is
known
that
the
mean