TGC
REPORT
No
.
31,
1981
RESEARCH
NOTES
14
like
Langford
(1948)
the
genotype
Cf
-
2Cf
-
2nene
(corresponding
to
Quadt
1953
=
NNhh)
for
the
3/16
necrotic
individuals
assuming
that
ne
must
be
carried
by
most
varieties
of
Lycopersicon
esculentum
and
Cf
-
2
by
"Atom"
.
His
explanation
"the
expression
of
ne
requires
the
presence
of
Cf
-
2"
is
to
some
extent
contradicting
because
one
would
not
follow
from
it
that
necrosis
is
really
produced
by
Cf
-
2
and
suppressed
by
Ne
.
Unfortunately,
so
far
as
we
know
nobody
has
taken
notice
of
ne;
however,
it
appears
to
be
a
rather
interesting
gene,
for
instance,
from
the
practical
point
of
view
because
of
the
suppression
of
necrosis
produced
by
resistance
factors,
or
theoretically
because
of
analytical
chances
for
investigating
the
"necrosis
suppressing
principle"
.
Are
there
possibly
similar
factors
in
close
linkage
of
those
immunity
genes
which
are
well
known
for
effecting
resistance
without
necrosis,
and
possibly
without
production
of
deleterious
"phytoalexins"?
In
order
to
get
an
approach
to
the
answer
we
selected
individuals
with
differing
necrotic
expression
from
a
cross
"Haubner's
Vollendung"
x
"Atom"
and
examined
the
offspring
from
selfing
in
the
field
for
necrosis
.
Having
also
examined
the
reaction
to
Cladosporium
fulvum
race
"0"
on
cuttings
of
the
same
plants
in
the
greenhouse,
we
identified
-
homozygotes
for
immunity
which
showed
no
or
only
very
small
sparsely
visible
necrotic
spots;
-
homozygotes
for
resistance,
showing
severe
necrosis;
-
different
types
of
non
-
resistant,
non
-
necrotic
homo
-
and
heterozygotes
.
Unfortunately
besides
race
"0"
we
had
available
for
testing
the
resistance
factor
only
races
"2
.
3"
and
"1
.
4"
which
were
kindly
provided
by
Mr
.
Hubbeling,
Wageningen,
Netherlands
.
As
the
immune
selections
were
resistant
to
races
"0"
and
"1
.
4"
(without
showing
necrosis)
but
susceptible
to
"2
.
3",
they
do
represent
Cf
-
2Cf
-
2NeNe
(according
to
Langford
1948)
or
NNHH
(according
to
Quadt
1953)
.
In
order
to
separate
cf
-
lcf
-
2NeNe
homozygotes
(=
nnHH
according
to
Quadt
1953)
from
the
other
susceptible
segregates,
38
testcrosses
were
made
between
susceptible
and
Cf
-
2Cf
-
2nene
(=
NNhh)
plants,
which
were
resistant
but
necrotic
.
Five
of
them
were
uniform
for
resistance
to
Cladosporium
fulvum
after
artificial
infection
with
race
"0",
so
representing
the
cf
-
2cf
-
2NeNe
homozygotes
.
These
were
crossed
to
varieties
known
as
carriers
of
Cf
-
1
as
"Leafmold
Resister"
and
"Stirling
Castle",
and
to
"V
121"
which
carries
Cf
-
3
.
After
infections
with
races
"0"
and
also
"2
.
3"
(in
the
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