Molecular Plant Breeding 2015, Vol.6, No.17, 1
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Table 3 Analysis of molecular variance (AMOVA) for the extraction of SSR variation among groups (populations) and among
individuals within populations
Grouping
Source of variation
d.f.
Sum of squares
Variance
components
Percentage of
variation
K=2 (2 pos and mixed)
Among populations
2
521.378
5.3344
15.3*
Within populations
181
5326.046
29.42567
84.65
Total
183
5847.424
34.76006
K=3 (3 pops and mixed
Among populations
3
1156.175
8.07679
23.66*
Within populations
180
4691.249
26.06249
76.34
Total
183
5847.424
34.139
K=4 (4 pops and mixed)
Among populations
4
1349.915
8.7638
25.86*
Within populations
179
4497.509
25.12575
74.14
Total
183
5847.424
33.88954
K=5 (5 pops and mixed)
Among populations
5
1450.722
8.93096
26.56*
Within populations
178
4396.702
24.70058
73.44
Total
185
5847.424
33.63154
K=5 (6 pops and mixed)
Among populations
6
1566.737
9.3348
27.85*
Within populations
177
4280.687
24.18467
72.15
Total
183
5847.424
33.51947
Cluster analysis (6 groups)
Among populations
5
1303.463
8.16166
24.26*
Within populations
177
4509.296
25.47625
75.74
Total
182
5812.76
33.63791
Analysis based on SPR(2 groups) Among populations
1
226.525
2.14151
6.49*
Within populations
181
5586.235
30.86318
93.51
Total
182
5812.76
33.00469
*p-value<0.0001
grain borer and the stem borers among tropical maize
germplasm (Arnason et al. 1994; Mwololo et al., 2010;
Tefera et al., 2011). This genetic diversity can be
exploited in breeding programs to introgress resistance to
field and postharvest insect pests into improved
varieties using conventional and genetic engineering
approaches (Dhliwayo and Pixley 2003).
Overall mean Roger’s genetic distance of 0.353
among pairwise comparisons of inbred lines, with the
vast majority (94.2 %) showing distances between
0.300 and 0.400 have been reported (Semagn et al.,
2012). This slightly differs from the average distance
(0.3012) obtained from the current study. The observed
lower genetic distance is likely due to the mixed
origin of the inbred lines and hybrids. Clustering of
the individual candidates among the wide germplasm
evaluated in relation to resistance to the maize stem
borer and postharvest insect pests was evident. Some
of the genotypes which had been bred for stem borer
and storage insect pests were resistant to both classes
of maize insects hence has the potential to breed for
multiple resistance. In addition, the clustering based
on the SSR marker conforms to the history of
generating the different genotypes. The grouping
based on the phenotypic traits did not show a clear
genetic differentiation with regard to specific
resistance traits of the six different groups from the
cluster analysis based on the SSR marker data. This is
in agreement with previous studies whereby there was
lack of clear clustering patterns based on phenotypes,
environmental adaptation and grain colour (Xia et al.,
2005). This can be explained by the fact that,
selectively neutral markers used were not subject to
selection and thus resistance, an adaptive trait had low
correlation with SSR data (Koebner et al., 2002). The
