cloned
Pto
gene
(CD186)
(Martin
et
al
.
1993)
.
All
plants
showed
resistance
to
fenthion
and
susceptibility
to
race
1
strain
T1
(Ronald
et
al
.
1992),
The
segregation
results
for
reaction
to
Pst
race
0
strain
PT11
and
for
probing
with
the
cloned
Pto
gene
are
summarized
in
Table
I
and
2
.
Resistance
to
Pst
race
0
and
CD186
(cloned
Pto
gene
from
chromosome
5)
showed
perfect
cosegregation
in
both
the
BC4
and
BC3F2
populations
indicating
that
race
0
resistance
from
L
hirsutum
P1134418
is
likely
allelic
to
Pto
.
We
therefore
designate
the
gene
from
L
.
hirsutum
as
Pto
h
.
Pto
h
is
similar
to
Pto
in
that
it
confers
a
dominant
resistance
to
race
0
but
is
ineffective
against
race
1
.
Pto
h
differs
from
Pto
in
that
it
is
not
associated
with
fenthion
susceptibility
.
The
region
of
chromosome
5
containing
the
Pto
h
gene
showed
skewed
segregation
in
favor
of
the
susceptible
(esculentum)
homozygotes
in
both
the
BC
4
(10
R/S:16
S/S)
and
the
BC
3
F
2
(13
RJR
-
28
R/S:
20
S/S)
generations
.
The
skewed
segregation
may
be
due
to
the
interspecific
origin
of
the
Pto
h
gene
and
may
account
for
the
high
level
of
skewing
towards
susceptible
types
in
the
early
backcross
generations
.
Literature
cited:
Laterrot
H
(1985)
TGC
Report
35:6
Laterrot
H,
Moretti
A
(1989)
TGC
Report
39:21
-
22
Laterrot
H,
Moretti,
A
(1992)
TGC
Report
42:26
-
27
Martin
G,
et
a[
.
(1993)
Science
262:1432
-
1436
Martin
G,
et
al
.
(1994)
Plant
Cell
6:1543
-
1552
Pitblado
RE,
MacNeill
(1983)
Can
J
Plant
Pathol
5:251
-
255
Ronald
PC,
et
al
.
(1992)
J
Bacterial
174:1604
-
1611
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