Basic HTML Version
Molecular Plant Breeding 2013, Vol.5, No.9, 47
-
63
http://mpb.biopublisher.ca
48
Institute
IRRI,
in
the
Philippines
in
collaboration with
many
national
institutes
to
develop
and
improve
rice
varieties
tolerant
to
salinity. This
has
led
to
the
release
of
varieties
such
as
FL478,
IR4630
-
22
-
2
-
5
-
1
-
3
(SAL
002),
PSBRc
88,
IR77644
-
B
-
9
-
3
-
3
-
21
-
15
-
2
-
AJY4
and
IR83415
-
B
-
SDO3
-
3
-
AJY3.
However
most
of
these
varieties
were
developed
with
limited
number
of
resistant
such
as Nona Bokra
or Pokkali
or
varieties
derived
from
these
parents
such
as
CSR27
(Negrao
et
al.,
2011),
There
is
the
need
to
broaden
the
genepool
of
rice
for
salinity
tolerance.
Hasawi
is
a
landrace
from
eastern
Saudi Arabia
and
characterized
by
its
strong
adaptability
to
soil
salinity
and
drought
making
it
a
plausible
donor
to
be
used
in
salinity
research.
Research
on
quantitative
trait
loci
QTL, mapping
for
salt
tolerance
in
rice
has
advanced
significantly
in
the
last
2
decades
(Zhang
et
al.,
1995;
Lin
et
al.,
1998;
Gong
et
al.,
1999;
Flowers
et
al.,
2000;
Prasad
et
al.,
2000;
Tuan
et
al.,
2000;
Koyama
et
al.,
2001;
Lang
et
al.,
2001; Masood
et
al.,
2004;
Yao
et
al.,
2005;
Sabouri
and
Sabouri,
2009;
Ahmadi
and
Fotokian,
2011;
Islam
et
al.,
2011);
but
only
few
studies
of
heterogeneous
quality
have
been
conducted
(Negrao
et
al.,
2011),
Several
QTLs
have
been
identified
for
salinity
tolerance
in
rice
using
different
mapping
populations
such
as
RIL,
DH
or
F
2:3
,
ranging
from
indicaxjaponica
originally
developed
for
other
purposes,
such
as
IR64×Azucena or Co39×Moroberekan.
Most
of
these
QTLs
compute
indices
for
plant
developments
under
normal
and
stress
conditions
www.Gramene,
Some
QTLs
have
been
detected
repeatedly
on
chromosomes
1,
4,
6,
and
7, whilst
none
have
been
found
on
chromosomes
8
and
11
and
very
few
on
chromosomes
2,
3,
5,
9,
10
and
12
(Negrao
et
al.,
2011),
QTL
studies
have
led
to
the
conclusion
that
different
loci
are
involved
in
the
different
plant
responses
under
salt
stress
(Haq
et
al.,
2010).
A
large
number
of
QTLs
have
been
detected
to
concentrate
on
the
segment
of
short
arm
on
chromosome
1
(Bonilla
et
al.,
2002,
Gregorio
et
al.,
2002,
Lin
et
al.,
2004;
Ren
et
al.,
2005).
More
recently,
the
use
of
single
nucleotide
polymorphisms
(SNPs),
due
to
their
high
level
of
informative
content,
has
led
to
identifying
various
QTL
in
rice.
The
advantages
of
using
recombinant
inbred
lines
RILs,
for
a QTL
analysis
are well
documented.
First,
multiple
selfing
processes
can
increase
the
number
of
recombination
events
(Soller
and
Beckmann,
1990),
which
results
in
a
finer
mapping
of
QTLs.
More
importantly,
once
RILs
are
established,
in
which
the
genotypes
of
all
lines
are
fixed
as
homozygotes,
these
lines
can
be
repeatedly
used
for
investigating
QTLs
of
various
phenotypes
under
different
environments.
Thus,
the
establishment
of
a
comprehensive
set
of
RILs
will
be
a
substantial
contribution
to
QTL
mapping
for
salinity
tolerance
in
rice.
The RILs
population
used
in
the
current
study
consists
of
300
lines
using
single
seed
descent
until
the
F
5
generation
developed
at
IRRI.
This
RIL
population
was
derived
from
a
cross
between
IR29
and
Hasawi.
IR29
is
an
IRRI-bred
indica
line
and
it
is
used
as
a
susceptible
check
in
salinity
experiments.
SNP-facilitated
allelic
diversity
analysis
have
revealed
that
Hasawi
is
an
Aus
cultivar;
suggesting
that
there
may
be
a
possibility
of
high
level
of
polymorphism
in
offspring
derived
by
crossing
Hasawi
with
indica
cultivars
(Thomson
et
al.,
2010a;
Platten
et
al.,
2013).
The
objectives
of
our
research
were
to
identify
and
map
QTL
controlling
salt
tolerance
at
early
seedling
stage
in
IR29×Hasawi
F
5
RIL
population
using
384
SNP
chip
under
hydroponic
conditions,
and
also
to
select
best
performing
RILs
for
their
further
use
as
breeding
materials
or
for
cultivar
development.
1 Results
1.1 Trait
Analysis
and
Performance
of
F
5
–derived
RILs
The
descriptive
statistics
of
the
qualitative
and
quantitative
traits measured
in
the F
5
derived–RILs
are
given
in
Table
1.
There
was
a
significant
variation
for
all
traits
in
these
RILs;
besides
we
also
observed
transgressive
for
all
traits
(Figure
1~Figure
4).
Ranking
of
F
5:6
RILs
for
salinity
damage
using
SES
.
Salinity
tolerance
was
rated
as
any
entry
having
an
SES
score
of
equal
to
that
of
the
tolerant
parent,
Hasawi
or
better
than
it.
The
tolerant
parent
Hasawi
had
a
score
of
4
and
IR29
had
7,
confirming
its
susceptibility
to
salinity.
Salinity
damage
scores were
given
to
each
RIL
according
to
their
plant
vigor,
leaf
chlorosis,
necrosis
and
general
physical
health.
The
mean
SES
score
for
the
RILs
was
6
but
with
a
wide