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Molecular Plant Breeding 2011, Vol.2, No.07, 41
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47
http://mpb.sophiapublisher.com
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stems and inflorescences as well as the edible parts.
The traits of the colors, size of stem and flowering
time are known as important morphological characters,
which were recognized as the criteria for classification
and identification of commercial products. The
classification of Caixin based on morphological
approach has somewhat differences with that of
Brassica
vegetable based on molecular marker (Guo
et al., 2002; Yang et al., 2006; Wang, 2006; Sun et al.,
2010). The reasons might refer to close relatives
between species. The previous studies RAPD and
ISSR motioned above were prevalent for the
classification of Caixin, which usually assigned Caxin
to the independent group or group together with other
non-heading Chinese cabbage. The reason for this
might be caused by the long term artificial selections,
plant introduction or natural variation (He et al., 2002;
Wang, 2006; Sun et al., 2001; Guo et al., 2002; Chu,
2002). It is obvious that genomic differences between
Caixin and other
Brassica
vegetables need to be
identified. As we know that artificial selection is
based on the natural and heritable variation in
systematic breeding program, which is dominant
approach in the Caixin breeding (Ma and Wang, 2006),
how to distinguish the variations or genetic diversities
among Caixin germplasms might be still a big
challenge to the breeders while they try to explore and
widen their genetic diversities in the future.
The previous results came from RAPD and ISSR
indicated Caixin’s genetic diversity was comparatively
low and there was no obvious grouping pattern in
classification at molecular level (Qiao et al., 1999; He
et al., 2002; Wang, 2006; Han et al., 2008; Ma, 2008;
Tan et al., 2009; Zhang et al., 2010; Sun et al., 2010).
There is few information about Caixin’s genetic
diversity based on AFLP data (Chu, 2002; Zhao et al.,
2005). In present research we selected 30 Caixin
collections from different sources to detect Caixin
genetic diversities using AFLP approach and to
evaluate the feasibilities of AFLP approach for
biodiverse study.
1 Results
1.1 AFLP polymorphism
In present study, 30 Caixins were analyzed with 25
selective primer combinations of AFLP (Table 1).
Total 116 0 bands were amplified in which 876 bands
were polymorphic bands, accounting for 76%. The
sizes of amplified bands ranged from 100 bp to 1 500
bp, while most of specific bands are located in the
ranges from 700 bp to 1 000 bp. The average number
of polymorphic bands for each primer combination is
44 in the range from 13 to 84. The mean
polymorphism rate of each primer combination was
up to 80% in the range from 56.8% to 97.1%. The PIC
values for each primer combination varied from 0.011 6
to 0.031 7 that the mean was 0.023 9. These parameters
showed that there were sufficient AFLP
polymorphisms existing in selected Caixin germplasms.
Each primer combination used in this research could
detect the genetic diversity of Caixin because there
were significant differences existing between the
tested primer combinations. To be as case, primer
combination, E-ATG/M-CTG, could reveal 97% AFLP
polymorphism in selected tested Caixin germplasms.
1.2 Genetic diversity analysis
GenAlEx 6.4 software was employed to calculate 30
Caixin’s genetic diversity (Table 2). The average
percentage of polymorphic loci was 85.33% in the
range from 51.6% (Lvbao 701) to 91.78% (Guiliu
October). The following parameters are including as
Na, Ne, I, He, GD and Gs. That is, the number of
different alleles (Na) 1.754 from 1.032 (lvbao 701) to
1.904 (Guiliu October), the number of effective alleles
(Ne) 1.544 from 1.211 (lvbao 701) to 1.665,
Shannon’s Information Index (I) 0.472 from 0.232
(lvbao 701) to 0.543 (Guiliu October) and He 0.363
from 0.165 (lvbao 701) to 0.426. The values of
genetic distance (GD) and genetic similarity (GS)
were 0.112 from 0.026 (CX 9
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1 and CX 6
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14) to
0.275 (Lvbao 701 and Australia 008) and 0.895 from
0.76 (Australia 008 and Caixingli Si Jiu) to 0.959,
respectively.
Analysis of Molecular Variance (AMOVA) for the 30
Caixins based on AFLP data derived from 876
markers indicated that almost 100 percentage of
variation was contributed by Caixin varieties (
Φ
pt
=0.006, P>=0.227) and lines (
Φ
pt=0.005, P>=0.653),
respectively.