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correlations (r=0.29 p≤ 0.05) were detected between SCA and heterosis data, demonstrating that the two data sets may be used in identification of similar lines. In this study, lines 16, 18, 38 and 40 showed positive SCA with both testers, and were grouped similarly based heterosis and SCA data sets across locations akin to other studies (Fato et al., 2012).
The high genetic variability for B. fusca resistance detected in the testcross hybrids clustering with the two testers are desirable characteristics for a good maize tester. However, some lines did not show heterotic orientation to both testers. Theoretically, these lines may be useful in breeding; however, in practice they would be disposed. In addition, these findings suggest that various lines and groups identified may be useful in B. fusca specific hybrid breeding programmes across the tropical environments where these borers occur. However, the results also showed that some lines may have had good general combining ability, but probably require all new testers with new genetic constitution to distinguish them for B. fusca resistance (Guimaraes et al., 2012). The challenge is occasioned by the many lines that were not classified by both testers at the two locations. In this study, the unclassified heterotic orientations suggest need for new testers with new inherent structures, since continuous introduction of new and diverse germplasm into breeding programs may render some testers insensitive to discriminating materials.
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resistance breeding programmes in the tropics. Similarly, using specific combining ability estimates, various heterotic orientations identified testcrosses that showed positive significant SCA effects for B.
fusca resistance and grain yield. These testcrosses may be evaluated further for B. fusca stem borer resistance and grain yield to confirm their stability. Finally, under artificial infestation conditions, it is desirable to consider grain yield in a hybrid breeding programme that emphasises B. fusca stem borer resistance.
93 References
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95 Appendix 3.
Table 3.14. List of germplasm used in the study
Entry No. Pedigree code¥ Entry No. Pedigree code
1 CKSBL10001 34 CKSBL10157
2 CKSBL10004 35 CKSBL10157
3 CKSBL10007 36 CKSBL10158
4 CKSBL10008 37 CKSBL10165
5 CKSBL10013 38 CKSBL10168
6 CKSBL10014 39 CKSBL10169
7 CKSBL10015 40 CKSBL10170
8 CKSBL10020 41 CKSBL10171
9 CKSBL10025 42 CKSBL10178
10 CKSBL10027 43 CKSBL10194
11 CKSBL10028 44 CKSBL10195
12 CKSBL10028 45 CKSBL10196
13 CKSBL10030 46 CKSBL10197
14 CKSBL10033 47 CKSBL10200
15 CKSBL10034 48 CKSBL10201
16 CKSBL10035 49 CKSBL10202
17 CKSBL10038 50 CKSBL10203
18 CKSBL10040 51 CKSBL10204
19 CKSBL10041 52 CKSBL10205
20 CKSBL10042 53 CKSBL10206
21 CKSBL10043 54 CKSBL10207
22 CKSBL10045 55 CKSBL10208
23 CKSBL10060 56 CKSBL10209
24 CKSBL10073 57 CKSBL10210
25 CKSBL10107 58 CKSBL10211
26 CKSBL10108 59 CKSBL10212
27 CKSBL10138 60 CKSBL10213
28 CKSBL10153 61 CKSBL10248
29 CKSBL10154 62 CKSBL10250
30 CKSBL10155 63 CKSBL10254
31 CKSBL10155 64 CKSBL10286
32 CKSBL10155 65 CKSBL10307
33 CKSBL10155 66 CKSBL10321
¥- full pedifgree information is available.
97