Genomics and Applied Biology 2018, Vol.9, No.4, 19-23
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1.2 Ratio of similarity coefficient of Nei based on SSR and AFLP
The results of ratio of similarity coefficient of Nei and of genetic distance in groups among 5 populations were
calculated based on
SSR and AELP (Table 2).
Genetic distance in groups among 5 populations was between
2.824 10 and 6.920 63,
with an average of
3.972 02±1.328 94 (Nei, 1972).
Genetic similarity coefficient was
between
0.928 10 and 0.945 45,
with an average of
0.937 92±0.005 77 (Nei, 1972).
Table 1 Ratio of genetic diversity of
Nile tilapia
based on SSR and AFLP
Generation
Ratio of polymorphic sites
Ratio of population specific
Fst
indices
Ratio of gene diversity
F
0
1.63489
1.32451
1.68103
F
6
1.67844
1.14868
1.68952
F
7
1.64310
1.29506
1.66648
F
8
1.60325
1.39944
1.58765
F
9
1.85616
1.08161
1.75833
Mean
1.68317
1.24987
1.67660
Table 2 Ratio of similarity coefficient of Nei (upper right) and of genetic distance (lower left) in groups
Generation
Nei (1972)
F
0
F
6
F
7
F
8
F
9
F
0
0.94409
0.94345
0.93829
0.93757
F
6
3.41597
0.93357
0.93375
0.94545
F
7
3.40496
5.36943
0.92810
0.94199
F
8
3.41667
4.92000
6.92063
0.93297
F
9
2.94562
2.82410
3.25283
3.25000
2 Discussion
2.1 Technical characteristics and influencing factors of SSR and AFLPmarkers
Analysis of population genetic diversity and genetic structure is the basis of utilization and protection of
biological germplasm resources. Domestic and overseas scholars carried out a detailed study on the genetic
diversity of various Bio-economies by using different methods, such as morphological features, genetic
relationship and biochemical indexes. And molecular markers provide a deeper technique for the analysis of
biological genetic diversity. Among all kinds of molecular marker techniques, SSR sequence has no protein
coding function in genome, and they are rarely limited by the pressure of natural selection during long biological
evolution. Thus, SSR has the characteristics of high mutation rate among individuals and populations. In the case
of different primer combinations and multiple pairs of primers, AFLP could detect much polymorphic loci, which
is very sensitive to the variation reaction among DNA samples. Its sensitivity could detect tiny genetic diversity
among closely related biological DNA samples. In some kinds of successful development of SSR Markers, such
as bean research field, SSR even surpasses AFLP to become the mainstream technique of population genetic
diversity analysis (Liu et al., 2014). Association application of SSR and AFLP is adopted in the research of high
demand, which proves the validity of SSR and AFLP in genetic diversity analysis (Du et al., 2003; Wang et al.,
2006; Wang et al., 2012; Li et al., 2014).
2.2 Further comparison between SSR and AFLP markers
Most of the current studies stayed at using SSR or AFLP alone to analyze genetic diversity within and among
populations of different species. There were few reports about association application of SSR and AFLP t. As for
the depth of the study, it was lack of the further comparative analysis of the SSR and AFLP results, and lack of the
horizontal comparison of related research. To some extent, it limited the reference and application value of the
research results. Further analysis of the results of different markers could help to understand the genetic structure
of the population completely and thoroughly. Xie (2014) used this method for the first time to make a pioneering
exploration (Xie et al., 2014; Xie and Li, 2014). The genetic diversity ratio within population calculated by SSR
and AFLP showed that the level of genetic diversity obtained by SSR was higher. This conclusion was similar to
that of other studies (Yuan et al., 2000; Jiang et al., 2007), which indicated that SSR has higher resolution in
genetic diversity analysis than AFLP. And in this study, we found that the index of polymorphic loci based on SSR
