Differential
response
of
resistant
lines
derived
from
the
L
.
pimpinellifolium
accession
L3708
and
L
.
hirsutum
accession
LA
1033
against
different
isolates
of
Phytophthora
infestans
in
detached
leaf
lab
assays
Kim,
M
.
J
.
,
Mutschler,
M
.
A
.
Dept
.
of
Plant
Breeding,
Cornell
University,
Ithaca,
NY
14853
The
disease
late
blight
(caused
by
the
pathogen
Phytophthora
infestans
)
is
an
increasingly
significant
problem
to
processing
tomato
production
.
Transfer
of
resistance
into
processing
tomato
lines
could
materially
reduce
reliance
on
chemical
sprays
for
control
of
this
disease
.
We
are
working
with
two
potential
sources
of
Late
Blight
resistance,
L
.
hirsutum
accession
LA
1033
and
the
L
.
pimpinellifolium
accession
L3708
.
The
first
source
is
the
L
.
hirsutum
accession
LA
1033
-
2,
a
sub
-
selection
of
LA
1033
created
by
Dr
.
R
.
Gardner,
N
.
C
.
These
sources
are
reported
to
hold
up
to
challenges
by
late
blight
in
a
number
of
locations
.
In
North
Carolina,
these
sources
of
resistance
have
held
up
under
conditions
in
which
Hawaii
7998
source
and
the
Ph2
gene
fail
(Gardner,
per
.
comm
.
)
.
Dr
R
.
Gardner
had
provided
us
with
a
series
of
cuttings
of
BC1F2
plants,
each
of
which
was
derived
from
the
cross
(and
subsequent
backcross)
of
one
of
the
resistance
sources
with
the
fresh
market
line
NC215
-
E,
a
VFF
early
blight
tolerant
elite
fresh
market
line
.
These
plants
were
used
in
further
backcrosses
to
processing
tomato
parents
to
transfer
the
resistance
to
processing
lines
fixed
for
resistance
.
These
lines
were
tested
in
lab
assays
using
a
series
of
isolates
of
the
pathogen
to
determine
if
either
of
the
sources
of
resistances
is
limited
in
utility
by
race
specificity
.
Greenhouse
grown
plants
were
tested
in
the
laboratory
by
detached
leaflet
droplet
tests
that
were
modified
from
those
reported
by
Mizubuti
and
Fry
(1998)
.
In
the
detached
leaflet
droplet
test
method,
tomato
leaflets
from
the
3
-
4
th
leaf
from
the
tip
were
placed
abaxial
surface
down
on
water
agar
plates
.
Care
was
taken
to
choose
flat
leaflets
.
Each
leaflet
was
inoculated
with
two
20
m
l
drops
of
30,000
sporangia/ml
.
(When
10,000,
20,000,
30,000
and
40,000/ml
concentrations
was
pre
-
tested
on
susceptible
plants,
escape
did
not
occur
using
the
30,000
and
40,000/ml
concentrations)
.
The
plates
were
incubated
upside
down
at
18
°
C
and
16hr
light