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Molecular Plant Breeding 2011, Vol.2, No.14, 75
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82
http://mpb.sophiapublisher.com
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1.3 Cluster analysis
The dendrogram for 30 Caixins was constructed
according to unweighted pair group method of
arithmetic averages (UPGMA) and Nei’s genetic
distance. The four groups were classified at the 0.17
threshold of Nei’s genetic distances by clustering
analysis based on UPGMA approach (Figure 1).
Group I was composed of eleven germplams, CX6
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6,
CX6
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6
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1, CX6
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7, CX6
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13, Si Jiu
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19, CX5
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12,
CX5
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14, CX9
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1, CX9
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4, Youqing no. 12, Lvbao 701.
Group II was composed of 15 germplasms, CX5
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3,
CX5
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4, Dong Guan 45 Days, Australia 50 Days,
Kuaida 28 Days, CX3
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6, New Zealand Si Jiu,
Caixingli Si Jiu, CX3
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6
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1, Australia 608, Australia
008, Hong Kong 45 Days, Mingyou 308 sweet, No. 31,
GX3
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1. Group III was composed of Youxin no. 2,
GX6
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14 and Guiliu October. And Group IV was
Teqing 60 Days only. The results showed that most
lines were grouped together with at least one of their
parents. Such as the serials lines of CX6 were
clustered with Si Jiu
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19. New Zealand Si Jiu, Si
Jiu
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19, Caixingli Si Jiu grouped in one cluster. The
results indicated there is very close relationship in the
tested Caixin germplasms.
2 Discussion
To assess the genetic diversity and genetic
relationship is essential for effectively utilizing
genetic germplasms in the breeding program. The
availability of agronomic morphological traits in
Caixin are so limited that molecular markers should
genuinely play more important roles in breeding
program. Most of studies on Caixin varieties and even
mutant lines derived from the induction by carrying
Space Shuttle were conducted by RAPD or and ISSR
(Ma, 2008). Although RAPD, ISSR and AFLP have
the common vantages that they do not need to any
background information of the genome in advance, the
results of the amplication are quit different even based
on same genomic DNA. In present work, AFLP
generated 1 160 bands by 25 primer combinations.
876 bands were polymorphic. It is obvious that AFLP
could reveal much more polymorphisms and that is
more effective (Wang, 2006; Tan et al., 2009; Zhang
et al., 2010; Sun et al., 2010). The PIC values indicated
that the efficiency of primer combinations was very
Figure 1 The dendrogram of the selected 30 Caixins based on
UPGMA
high and most of primer combinations had relatively
high discriminatory ability. Due to the significant
correlationship and comparability between RAPD and
AFLP (Zhang and Yang, 2008), comparative studies
on the genetic variation had been conducted among
AFLP, RAPD (Han et al., 2008; Ma, 2008; Tan et al.,
2009), ISSR (Ma, 2008; Sun et al., 2010,) and SRAP
(Ma, 2008). The results showed that the parameters,
such as Na, Ne, He, I calculated based on AFLP data
were higher than that of others. This results illustrated
that AFLP had more powerful to uncover more
genetic diversity. AMOVA of AFLP in this work
revealed almost 100% genetic variation existing
within whatever varieties or lines, which suggested
that strong selection pressures might have contributions
to the low levels of genetic diversity in Caixin. Be a
kind of non-heading variety, Xiaobaicai,
Brassica