sterile,
producing
no
detectable
pollen,
and
4
were
fertile
.
The
nature
of
the
cross
suggested
the
sterility
was
of
a
dominant
nature,
and
the
frequency
of
steriles
was
likewise
consistent
with
the
predicted
1:1
ratio
(X2
=
0
.
5,
not
significant)
.
Larger
BC
4
,
and
BC
5
populations
produced
a
pooled
segregation
of
124
steriles
139
fertiles,
results
consistent
with
a
monogenic
dominant
(X
2
=0
.
75,
not
significant),
for
which
we
propose
the
gene
symbol
Ms
-
51
.
Surprisingly,
the
original
F,
plant
was
sufficiently
male
-
fertile
to
permit
direct
backcrossing
as
stamina
parent
to
VF36;
this
apparent
lack
of
Ms
-
51
expression
suggests
the
presence
of
a
restorer
gene(s)
in
the
S
.
lycopersicoides
genome
.
Anthers
of
Ms
-
51/+
plants
are
noticeably
thinner
than
normal,
but
not
significantly
shortened,
hence
stigmas
are
inserted,
as
in
VF36
.
No
detectable
pollen
can
be
collected
by
vibration
or
dissection
of
anthers
.
No
mature
pollen
grains
are
observable
under
the
microscope
following
squashing
of
anthers
in
acetocarmine;
only
very
small
immature
or
abortive
grains
or
clumps
of
cells
are
seen
.
The
phenotype
of
Ms
-
51
is
similar
to
that
of
Ms
-
48
(Rick
1987),
the
only
other
dominant
male
-
sterility
described
in
tomato,
suggesting
they
might
be
allelic
.
Literature
Cited
Rick,
C
.
M
.
1987
.
A
dominant
male
sterility
(Ms
-
48)
gene
.
TGC
37:62
.
Tolerance
to
Botrytis
cinerea
in
L
.
esculentum
x
S
.
lycopersicoides
hybrids
.
Chetelat,
R
.
T
.
and
Stamova,
L
.
Dept
.
of
Vegetable
Crops,
University
of
California,
Davis,
CA
95616,
USA
.
We
know
of
no
reports
of
resistance
to
gray
mold
(
Botrytis
cinerea
)
in
tomato
or
its
wild
relatives,
other
than
that
of
Farley
et
al
.
(1976)
.
Observations
made
during
regular
seed
increases
of
S
.
lycopersicoides
at
the
C
.
M
.
R
.
TGRC
suggested
this
species
might
be
resistant
or
tolerant
to
stem
infection
by
B
.
cinerea
.
Accordingly,
we
screened
sesquidiploid
and
diploid
L
esculentum
x
S
.
lycopersicoides
hybrids,
representing
accessions
LA1964,
LA2408,
and
LA2951
(Rick
et
al
.
1986;
Chetelat
et
al
.
1989;
Chetelat
at
al
.
unpublished,
respectively),
for
resistance
to
gray
mold
.
B
.
cinerea
attacks
all
the
aboveground
parts
of
the
tomato
plant,
including
leaves,
stems
and
fruit;
the
stem
lesions
can
girdle
the
shoot,
leading
to
wilting
and
death
.
The
intergeneric
hybrids
are
generally
sterile,
and
produce
few
fruits
.
For
these
reasons,
we
screened
plants
for
reaction
to
stem
infection
by
B
.
cinerea
.
The
method
involves
inoculation
of
the
cut
petiole
.
surfaces
of
stem
cuttings
with
agar
plugs
containing
B
.
cinerea
mycelia
.
The
cuttings
are
kept
in
boxes
with
vermiculite
at
90
-
100%
RH
for
2
days,
after
which
time
the
agar
plugs
are
removed
.
Two
isolates
of
B
.
cinerea
were
used:
TI
from
tomato
and
DEL
-
11
from
grape
.
The
first
symptoms
appeared
as
elliptical
water
-
soaked
lesions
on
the
stem,
the
length
of
which
were
measured
at
3
and
6
days,
approximately
.
The
lesions
enlarged
from
3
to
6
days
in
the
susceptible
cultivar
VF36,
whereas
no
progression
of
the
disease
was
seen
on
the
S
.
lycopersicoides
hybrids
.
After
6
days,
the
average
lesion
length
on
VF36
was
approximately
3
times
greater
than
on
cuttings
from
the
diploid
or
sesquidiploid
F,
intergeneric
hybrids
.
Having
obtained
some
evidence
of
tolerance
in
the
parental
hybrids,
we
have
begun
to
screen
derivatives
from
the
backcrosses
to
