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efficiently. In peanut,
ahFAD2A
and
ahFAD2B
have been identified on the A and B genomes,
respectively, and the mutant alleles are reported
to confer a high oleic/linoleic acid ratio (O/L
ratio) (Lopez et al. 2000; Bruner et al. 2001;
Lopez et al. 2002; Patel et al. 2004;Chu et al.
2009; Barkley et al. 2010). In previous stud-
ies, cleaved amplified polymorphic sequences
(CAPS), allele specific polymerase chain reac-
tion (AS-PCR), and real-time PCR genotyp-
ing assays were developed for the
FA D 2 A
and
FA D 2 B
genes (Chu et al. 2007; Chu et al. 2009;
Barkley et al. 2010; Chen et al. 2010; Chu
et al. 2011). Accordingly, MAS for high O/L
ratio appears to be already in practical use. Chu
and colleagues (2011) reported gene pyramid-
ing by MAS for nematode resistance and high
O/L content.
MAS is classified into two categories: marker-
assisted backcrossing selection (MABS) and
marker-assisted recurrent selection (MARS).
Generally, the former is employed for the
improvement of traits controlled by major genes,
while the latter is for pyramiding multiple QTLs.
Because previous studies suggest that the O/L
ratio is controlled by the two candidate
FA D 2
genes, MABS is favorable for the improvement
of the O/L ratio in peanut. In this chapter, MABS
for a high O/L ratio in peanut is demonstrated
with a breeding line showing a high O/L ratio
and an elite line with medium O/L ratio as
donor and backcross parents, respectively. The
MABS program was started in 2007, and the
number of DNA markers developed was consid-
erably lower at that time compared to the present.
Polymorphic DNA markers and a linkage map
were developed in parallel with the MABS
program.
crossed in 2007 at Chiba Prefectural Agricul-
ture and Forestry Research Center. 'Nakateyu-
taka,' which was used as a seed and backcross
parent, is one of the leading varieties in Japan,
whose agronomic type is Virginia and shows a
normal O/L ratio (O/L
1.16). It exhibits large
seed size (approx. 89g/100 seeds), light brown
seed coat color, short length, and
erect
branches.
'YI-0311' is a breeding line of the Chiba Pre-
fectural Agriculture and Forestry Research Cen-
ter with a high O/L ratio (O/L
=
=
48.2), and used
as a pollen and donor parent. It is Southeast-
runner type, and shows small seed size (approx.
50g/100seeds), light brown seed coat color, and
long and prostate branches. The F
1
seeds were
sown in the field in May 2008, and F
2
seeds
were harvested in October. The O/L ratios of the
F
2
seeds were analyzed, and F
2
seeds showing
a high O/L ratio were sown in the greenhouse
during the off-season for the production of F
3
seeds. In parallel, the availability of the
FA D 2
genes as selection markers for a high O/L ratio
was confirmed (details are described in the next
sections). The F
3
seeds were sown in the field
in 2009 and backcrossed with 'Nakateyutaka'
to start backcross (BC) Cycle 1. The harvested
BC
1
F
1
seeds were grown in the greenhouse dur-
ing the off-season, and genotypes were analyzed
using genome-wide (GW) DNA markers. The
BC
1
F
2
seeds harvested from the selected BC
1
F
1
plants based on their GW genotypes were sown
in pots, and the
FA D 2
loci genotypes were inves-
tigated. The BC
1
F
2
plants showing 'YI-0311'
genotypes on the
FA D 2
loci were selected and
transplanted to the field for the next backcross-
ing cycle (BC Cycle2). At present, BC Cycle 2
is complete and BC Cycle 3 is in process.
Polymorphic Analysis of the
FAD2Genes
Materials and Methods
The
previously
reported
single
nucleotide
Breeding Scheme
polymorphism
(SNP)
in
ahFAD2A
and
the
The breeding scheme of the MABS program
is
transposon
insertional
polymorphism
in
shown
in
Figure
11.1.
The
two
parental
ahFAD2B
were
investigated,
based
on
the
lines,
'Nakateyutaka'
and
'YI-0311,'
were
existence
of
polymorphisms
in
the
parental
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