Screening
tomato
mutants
for
abnormalities
in
VA
mycorrhizal
symbiosi
.
Barker,
S
.
J
.
1
,
Stammer,
B
.
,
O'Connor,
P
.
,
Dispain,
I
.
,
and
Smith,
S
.
E
.
2
Departments
of
Plant
Science
1
and
Soil
Science
2
,
The
University
of
Adelaide,
S
.
Australia,
5064
Vesicular
-
arbuscular
mycorrhizal
(VAM)
symbiosis
is
a
mutualistic
plant
-
fungal
interaction
that
occurs
in
more
than
80
%
of
extant
plant
species
and
that
has
also
been
shown
in
some
of
the
earliest
land
plant
fossils
(Harley
and
Smith
,
1983
;
Remy
et
al
.
,
1994)
.
Despite
their
extensive
co
-
relationship,
and
although
the
fungal
partner
cannot
yet
be
cultured
in
the
absence
of
a
plant,
many
plant
species
are
not
obligate
symbionts
.
Thus,
at
least
some
of
the
plant
genes
that
are
required
for
successful
establishment
of
the
symbiosis
are
expected
to
be
identifiable
by
mutation
analysis
.
Until
recently,
virtually
no
molecular
study
of
VAM
had
been
attempted,
due
at
least
in
part
to
the
recalcitrance
of
the
fungus
to
axenic
culture
.
However,
with
the
development
of
a
rapid
synchronous
infection
method
(Rosewame
et
al
.
,
1996),
we
have
initiated
several
projects
in
this
area
of
research
.
Tomato
plants
are
natural
VAM
hosts
and
show
a
reasonable
growth
response
when
infected
(Rosewame
et
aL,
1996)
.
In
order
to
identify
genes
that
might
be
important
in
the
symbiosis,
we
have
been
screening
a
Fast
Neutron
mutagenised
population
of
Rio
Grande
76R,
that
had
provided
several
distinct
mutations
in
Pto
and
Prf
(Salmeron
et
al
.
,
1994),
for
altered
VAM
symbiosis
.
So
far,
from
a
preliminary
screening
of
209
families,
we
have
identified
10
families
which
contain
putative
mutations
in
ability
to
form
the
symbiosis
with
the
VAM
fungus
Glomus
mosseae
,
and
these
are
currently
being
further
characterized
.
In
addition
to
the
mutant
population,
we
have
screened
several
genetic
marker
stocks
and
root
morphology
mutants
for
their
ability
to
form
VAM
symbioses
.
The
accessions
screened
and
their
designated
mutations
are
listed
in
Table
1
.
None
of
these
stocks
show
any
abnormality
in
infection
morphology,
as
might
be
expected
from
the
lack
of
host
specificity
demonstrated
by
the
fungus
.
We
are
interested
in
screening
biochemical
mutants,
such
as
those
with
altered
root
exudates,
or
mutants
that
have
altered
phosphate,
photosynthate
or
micronutrient
status,
as
these
traits
may
play
a
direct
role
in
establishment
of
a
successful
symbiosis
.
Collaborative
interactions
are
of
particular
interest
to
us,
and
we
would
appreciate
contact
from
anyone
holding
mutants
of
these
types
.
Literature
cited:
Harley,
J
.
L
.
,
Smith,
S
.
E
.
1983
.
"Mycorrhizal
Symbiosis"
Academic
Press,
London
Remy,
W
.
,
Taylor,
T
.
N
.
,
Hass,
H
.
,
Kerp,
H
.
1994
.
Proc
.
Natl
.
Acad
.
Sci
.
U
.
S
.
A
.
,
91,
11841
-
11843
Rosewame,
G
.
M
.
,
Barker,
S
.
J
.
,
Smith,
S
.
E
.
1996
.
In
Preparation
Salmeron,
J
.
M
.
,
Barker,
S
.
J
.
,
Carland,
F
.
M
.
,
Mehta,
A
.
Y
.
,
Staskawicz,
B
.
J
.
1994
.
Plant
Cell,
6,
511
-
520
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