from
the
region
between
CT71
and
CT220
.
In
a
population
of
>200
L
.
esculentum
backcross
plants
segregating
for
Sw
-
5,
we
identified
only
two
plants
with
probable
crossover
events
between
Sw
-
5
and
the
0
.
94
kbp
421
R
band
.
Additional
analyses
have
determined
that
the
TSWV
resistance
phenotype
for
these
plants
was
incorrectly
diagnosed
.
Thus,
the
genetic
distance
in
an
L
.
esculentum
population
is
<1
cM
between
the
421
bands
and
Sw
-
5
.
We
have
found
the
specific
primers
to
be
highly
reliable
in
a
number
of
different
buffers
and
amplification
conditions
.
The
co
-
dominant
resistant
and
sensitive
specific
bands
differ
in
size
by
0
.
04
kbp
.
Therefore,
care
must
be
used
in
the
selection
of
gel
electrophoresis
conditions
in
order
to
distinguish
homozygous
resistant,
homozygous
susceptible,
and
heterozygous
plants
.
Literature
Cited:
Boiteux,
L
.
S
.
and
L
de
B
.
Giordano
.
1993
.
Euphytica
71:151
-
154
Stevens,
M
.
R
.
,
S
.
J
.
Scott
and
R
.
C
.
Gergerich
.
1992
.
Euphytica
59:9
-
17
.
Stevens,
M,
R
.
1993
.
Ph
.
D
.
Dissertation,
University
of
Arkansas,
Fayetteville,
AR
.
92
pp
.
Stevens,
M
.
R
.
,
E
.
M
.
Lamb
and
D
.
D
.
Rhoads
.
1995
.
Theor
.
Appl
.
Genet
.
90:451
-
456
.
Stevens,
M
.
R
.
,
J
.
W
.
Scott,
P
.
D
.
Griffiths,
D
.
K
.
Heiny
and
D
.
D
.
Rhoads
.
1996
Acta
Hortic
(In
Press)
.
van
Zijl,
J
.
J
.
B
.
,
S
.
E
.
Bosch
and
C
.
P
.
J
.
Coetzee
.
1986
.
Acta
Hortic
.
194:69
-
75
.
Pto
h
,
an
allele
of
Pto
conferring
resistance
to
Pseudomonas
syringae
pv
.
tomato
(race
0)
that
is
not
associated
with
fenthion
sensitivity
Tanksley
S,
Brommonschenkel
S,
Martin
G
.
Department
of
Plant
Breeding
and
Biometry,
Cornell
University
Department
of
Agronomy,
Purdue
University
Pto
is
a
dominant
gene
on
chromosome
5
conferring
resistance
to
Pseudomonas
syringae
pv
.
tomato
(race
0)
(Pitblado
and
MacNeill
1983)
.
It
has
also
been
shown
that
Pto
confers
susceptibility
to
the
organophosphate
insecticide,
fenthion
(Laterrot
1985,
Laterrot
and
Moretti
1989)
.
Recent
molecular
studies
have
shown
that
resistance
to
Ps
pv
tomato
and
susceptibility
to
fenthion
is
conferred
not
by
a
single
gene,
but
two
tightly
linked
and
functionally
similar
genes
(
Pto
and
Fen
)
(Martin
et
al
.
1994)
.
Thus
far
there
have
been
no
reported
successes
in
breaking
the
linkage
between
Pto
and
Fen
.
Recently
Laterrot
and
Moretti
(1992)
reported
that
several
accessions
of
L
hirsutum
appear
to
be
