Basic HTML Version
Genomics and Applied Biology, 2011, Vol.2 No.6
http://gab.sophiapublisher.com
- 37 -
1.4 Clustering analysis of the NILs derived from
the three genetic backgrounds
Based on the amplified results by molecular markers,
the tree diagram was clustered by using cluster
software (Figure 3). The results showed there were
quite differences between the first and third genetic
backgrounds. All lines with the same genetic background
were grouped with the donor together. The correlation
efficiency between the group T78 and ZS9 was 0.73,
which indicated that two genetic backgrounds had
high correlation. Both groups of T78 and ZS9 had
0.54 correlation efficiency with T84 group which
presented quite difference. Thus we obtained two NIL
lines with different genetic backgrounds
fpr
restore
gene of MI CMS system in this research. Each
candidate NILs in different background had correlation
with parents, and the difference between the lines and
donor was amplified a little. Genetic similarity efficiency
of candidate lines from T78 group ranged from 84.50
to 91.47% with an average of 86.78%, the lines closest
to T78 were wh3, wh13 and wh15. Candidate lines
from T84 group had relatively high genetic similarity
Figure 3 Cluster diagram of 24 NILs of restore genes based on
the data of molecular markers
efficiency, ranged from 91.25 to 92.87% with an
average of 92.38%, the lines closest to T84 were wh59,
wh71 and wh77. Candidate lines from ZS9 group had
the highest genetic similarity efficiency, ranged from
95.66% to 98.78% with an average of 98.14%, the
lines closest to ZS9 were wh118, wh123 and wh127.
2 Discussions
2.1 Analysis on effectiveness of backcross method
to build the NILs of restorer gene rapeseed
Continuous backcross method is a classic approach to
build near-isogenic lines of a crop trait, but for different
traits, the difficulty of building strategy would be
different, the building effect would be also quite
different. For plant height and leaf shape, etc. these
traits are visible to be easily selected in the backcross
progeny with the naked eye (Zeng et al., 2006; Pu,
2001), so it is relatively easy to be built. Whereas for
the traits of disease resistance and other traits that is
invisible (Jin et al., 2007), the target traits are required
to be examined in the backcross progeny before making
a selection, and then advance the next backcross step,
so it is more difficult to build NILs for such traits,
which might take more time and be influenced by
more factors. It might be more likely to choose the
wrong target individual in the backcross resulting in
failure building.
In this study, based on the principle of " co-existence
of the sterile genes outside nucleus of cell and restorer
genes inside nucleus of cell can exhibit the fertility"
(Fu, 2000), we used Ning R7 as the female parent and
sterile gene outside nucleus of cell as internal marker
to simply select fertile individual to be as plant for
continuing backcross, so that the restore gene will be
guaranteed without loss, thus the NILs for the restore
gene will be effectively built. In this study, the
detections of fertility separation conducted in BC
5
F
2
and BC
6
F
1
generations have fully proved the existence
of restorer genes. Overall, using this method to build
NILs of restore gene has the following four advantages:
(1) Significantly reducing the workload for detecting
restorer gene in the offspring. Conventional approach
need to conduct test cross for backcross progeny in
order to prove the target line had the existence of
restorer genes for advancing backcross, which is
time-consuming and labor-intensive; (2) Completely