The objectives of the study were to evaluate the adaptability of 17 experimental maize genotypes
under the maize growing environments of Ethiopia, to select the best hybrids for commercial
production, to utilize various statistical procedures for analyzing G x E interactions and yield
stability of Ethiopian maize hybrids across nine environments and to indicate breeding strategies
for releasing genotypes with adaptation to target environment.
Seventeen experimental maize hybrids, including a locally released standard check, were
evaluated for grain yield in a mid altitude areas of Ethiopia, for a period of three years (2004 to
2006) across three locations. The genotypes were planted in a completely randomized block
design. G x E interactions and variance components were calculated using factorial analyses.
Stability parameters were calculated using various parametric and non-parametric methods.
While, a cluster analysis was done to classify the different genotypes and environments. The
computer programmes, Agrobase Generation II (Agronomix, 2008), SAS (SAS Institute Inc.,
2003) and NCSS 2004 (Hintze, 2001) were utilized to perform the different analyses.
The mean squares for G x E interaction were found to be highly significant for yield
including the variation among the genotypes (G). The Location (L) and Location x Year (L x Y)
interactions have the largest components of variance for grain yield, which is an indication of
the variation among testing sites and year to year fluctuation of the weather. The experimental
maize hybrid PR1 (mean yield =7.14 t ha-1) was found to be the highest yielder followed by
PR13 (6.77 t ha-1) .This result shows the potential of the experimental genotypes to be released
for commercial production.
Highly significant correlations (P<0.01) was obtained among Eberhart and Russellâs
deviation from regression (S2
di), Wrickeâs ecovalence (Wi), Shuklaâs ( ) 2
i s stability variance and
AMMI Stability Value(ASV). Mean yield and Lin and Binnsâs cultivar superiority performance
(Pi) showed high correlations but they showed no correlations with the rest of the stability
parameters. The non-parametric measure of Nassar and Hühnâs absolute rank difference S(1)
and variance of ranks S(2) was significantly correlated (P 0.05) with ASV, however they did
not correlate with the rest of the parametric measures. Based on the different stability parameters, hybrids PR1, PR13 and BH540 were found to
be more stable and responsive to favourable environments while SE21 and SE22 hybrids showed
their stability in the low yielding environments. Since, ASV showed higher correlations with
both parametric and non-parametric measures, and the mean yield, it is recommended to use
ASV as a stability parameter in identifying stable genotypes from multi-environment trials.
The analysis of variance for the AMMI model indicated highly significant differences
between genotypes and environments as main effects and the interaction effect of G x E was also
highly significant. The first two interaction principal component axes (IPCA) of the AMMI
model together accounted between 34% and 56% of the total G x E interaction sum of squares
for grain yield. The AMMI biplot categorized the genotypes PR1, SE4, PR2, PR3, BH540 and
PR13 as well adapted to favourable environments with above average yield.
Hierarchical clustering using unweighted pair group method with arithmetic average
(UPGMA) grouped the genotypes into five and the environments into three clusters.
The results from the study of optimum allocation of resources indicated that allocation of
two or three replications, three to five locations for three to four testing years will give adequate
information for yield estimates, help to minimize trial costs and provide more precise data for
variety release decisions in Ethiopian condition. The research also proved that locations-years
tradeoffs are more effective than locations/years-replications tradeoffs in getting statistically
efficient data from a maize yield trial.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-09062010-121424 |
| Date | 06 September 2010 |
| Creators | Issa, Abdurahman Beshir |
| Contributors | Prof MT Labuschagne, Prof CS van Deventer |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-09062010-121424/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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