Marker-Assisted Backcrossing Selection for High O/L Ratio in Cultivated Peanut - Translational Genomics for Crop Breeding: Abiotic Stress, Yield and Quality - page 185

from crosses between 'Nakateyutaka' and 'YI-
0311.' An SSR marker, PM204, which showed
polymorphisms between the parents, was used
for genotyping of the seeds, and 34 of the 58
seeds were confirmed as hybrid. Six F 2 seeds
were obtained from each of the 34 F 1 plants, thus,
204 F 2 plants were obtained in total. Of the 204,
seven F 2 lines exhibited a high O/L (24.8

of the 19 GW markers. The 19 GW mark-
ers were screened from the 42 markers used
in the selection of BC 1 F 1 plants. The average
homozygous backcrossing ratio was 62.9% in
all BC 1 F 2 plants, while it was 70.2% in the
selected eight BC 1 F 2 plants. 'Nakateyutaka' was
then backcrossed to the eight BC 1 F 2 plants, and
26 BC 2 F 1 plants were developed. Thirty-four
markers selected from the 42 markers tested in
the BC 1 F 1 were used for GW genotype analysis,
and 10 BC 2 F 1 plants were selected. The average
homozygous backcrossing ratio was 83.5% in all
BC 2 F 1 plants, while it was 87.9% in the selected
10 BC 2 F 1 plants. A total of 205 BC 2 F 2 plants
were developed from the 10 BC 2 F 1 plants, and
nine of the 205 showed homozygous 'YI-0311'
genotypes on the FAD2 loci. All nine BC 2 F 2
plants were designated for use in the next BC
Cycle3; the GW genotypes of BC 2 F 2 plants were
therefore not analyzed.

6.8
on average) ratio and had homozygous 'YI-0311'
genotypes on the two FA D 2 loci (Figure 11.4).
Three of the seven F 2 plants were selected based
on plant vigor growing in the greenhouse dur-
ing off-season. The F 2 plants came into bloom
in January 2009 and F 3 seeds were obtained
in May 2009. Theoretically, F 2 plants could be
used as parents of BC 1 F 1 , however, we used F 3
generation for backcrossing, largely because of
insufficient temperature in the greenhouse for
obtaining a high success ratio of backcross-
ing. Therefore, four F 3 seeds were generated
from each of the three F 2 plants in the green-
house during off-season and were sown in the
field, then crossed with 'Nakateyutaka.' A total
of 108 BC 1 F 1 seeds were developed from the
12 F 3 plants, and genotypes were evaluated
using 15 SSR and 27 transposon markers. Of
a total of 42 markers, 33 were codominant poly-
morphic markers, while four and five markers
were dominant markers of 'Nakateyutaka' and
'YI-0311,' respectively. The six markers iden-
tified the homozygous genotype of 'Nakateyu-
taka,' and the other 36 markers showed poly-
morphisms within the BC 1 F 1 plants. Twelve of
the 108 BC 1 F 1 plants were selected according to
the genotypes. The average ratio of the markers
showing homozygous 'Nakateyutaka' genotypes
(hereafter referred to as homozygous backcross-
ing ratio) was 55.4% in the all BC 1 F 1 plants,
while that in the selected 12 BC 1 F 1 plants was
62.9%.
A total of 178 BC 1 F 2 plants were developed
from the 12 BC 1 F 1 plants, and 16 of the 178
showed a homozygous 'YI-0311' genotype on
the FA D 2 loci. In order to increase the homozy-
gous backcrossing ratio, eight of the 16 BC 1 F 2
plants were selected based on the genotypes

±

Transition of GW Genotypes
in the MABS

A linkage map, which had been developed based
on 186 F 2 plants during the MABS process,
was constructed in 2011. A total of 326 segre-
gated loci were mapped onto 19 linkage groups
(LGs) on 1332.9 cM. Homeologous group (HG)
numbers of the LGs were identified based
on previously published maps (Moretzsohn
et al. 2005; Fonceka et al. 2009; Leal-Bertioli
et al. 2009; Moretzsohn et al. 2009; Varsh-
ney et al. 2009). Three corresponding LGs
were generated in HG 2 (HG2.1, HG2.2, and
HG2.3), while single LGs were developed in
HG6 (LG6.2) and HG7 (LG7.1). No correspond-
ing LG was identified as HG10, and one LG
that showed no correspondence to previously
reported maps was named LGX. The two FA D 2
loci were mapped onto LG9.1 and LG9.2.
The average ratios of alleles derived from
the donor parent 'YI-0311' (hereafter AR y )on
mapped loci are shown in Figure 11.5 for 17
LGsoftheF 2 and the BC 2 F 1 populations. The
numbers of genotyped plants in the populations