1997))
DNA
analysis
and
GPI
tests
indicate
that
US17
may
have
been
derived
from
US
-
6
or
US
-
8
.
US
-
17
was
used
for
lab
assays
of
detached
leaves
from
N
.
Y
.
field
and
greenhouse
grown
plants
in
1998
.
DR4B:
isolate
recently
collected
in
the
Dominican
Republic
.
This
isolate
is
very
virulent
on
tomato
and
is
of
the
A1
mating
type
Table
1
.
Response
of
resistant
and
control
lines
against
different
isolates
of
Phytophthora
infestans
in
detached
leaf
laboratory
assays
.
New
Yorker
WV63
L
.
pimp
L
.
hirsutum
Isolate
Pik
Rite
VFT
Vendor
Ph
-
1
Ph
--
2
L3708
derived
LA1033
-
2
derived
US
-
7
S
S
S
S
R
R*
US
-
8
S
R
M
M
R
R
US
-
11
S
S
S
M
R
R
US
-
17
S
S
S
M*
R
R*
DR4B
N
.
A
.
S
S
S
R
NA
S:
susceptible,
M:
moderately
resistant,
R:
highly
resistant
M*
variable
between
susceptible
and
moderately
resistant
R*
variable
between
resistant
and
moderately
resistant
NA
data
not
available
Table
1
gives
a
summation
of
multiple
tests
of
these
isolates
on
control
and
resistant
tomato
lines
.
The
susceptible
control,
Pik
-
Rite,
uniformly
showed
strong
susceptible
reactions,
indicating
that
the
screens
were
reliable
.
In
the
droplet
assay
using
susceptible
leaflets,
hyphae
overrun
the
leaf
surface
causing
a
fuzzy
appearance,
and
high
numbers
of
sporangia
are
produced
within
4
to
5
days
after
inoculation,
even
though
leaf
tissues
remain
green
.
It
was
a
surprise
that
Vendor
is
resistant
to
the
potato
stain,
US
-
8
.
However,
Vendor
reputedly
has
the
Cf
-
9
gene,
which
a
recent
report
indicated
produces
a
protein
that
detects
the
INF1
protein
of
Phytophthora
infestans
(Kamoun,
Honee
et
al
.
1999)
.
Neither
the
Ph
-
1
nor
the
Ph
-
2
sources
had
strong
resistance
to
any
of
the
isolates
used
in
our
lab
assay
.
This
is
in
agreement
with
tests
by
other
groups
.
The
breeding
lines
with
the
L3708
-
derived
resistance
were
remarkable
in
that
they
were
uniformly
and
fully
resistant
to
all
isolates
of
the
pathogen
tested
.
We
intend
to
test
with
additional
highly
virulent
isolates
from
diverse
locations
.
However,
at
this
point
we
cannot
identify
an
isolate
that
will
overcome
this
source
of
resistance
.
Leaflets
from
lines
carrying
resistance
from
L
.
pimpinellifolium
L3708show
small
black
lesions
by
3
to
4
days
.
This
spot
can
expand
somewhat
thereafter,
but
little
fuzziness
is
observed,
and
sporangia
counts
per
leaflet
are
reduced
100
fold
compared
to
those
of
the
susceptible
controls
.
The
lines
derived
from
L
.
hirsutum
LA
1033
-
2
do
not
have
as
strong
a
resistance
as
that
derived
from
L
pimpinellifolium
L3708
.
Leaflets
from
lines
carrying
resistance
from
L
.
hirsutum
LA
1033
-
2
showed
reactions
that
are
similar
in
appearance
and
timing
to
those
from
lines
derived
from
L
pimpinellifolium
L3708
except
that
a
yellowish
region
surrounds
the
black
lesions
