Show simple item record

dc.contributor.advisorDeventer, C. S.
dc.contributor.advisorLabuschagne, M. T.
dc.contributor.authorIssa, Abdurahman Beshir
dc.date.accessioned2015-08-18T15:47:32Z
dc.date.available2015-08-18T15:47:32Z
dc.date.issued2009-07
dc.identifier.urihttp://hdl.handle.net/11660/924
dc.description.abstractEnglish: 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 Russell’s deviation from regression (S2 di), Wricke’s ecovalence (Wi), Shukla’s ( ) 2 i s stability variance and AMMI Stability Value(ASV). Mean yield and Lin and Binns’s 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 Hühn’s 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.en_ZA
dc.description.abstractAfrikaans: Die doel van die studie was om die aanpasbaarheid van 17 eksperimentele mieliegenotipes in veskillende omgewings in Ethiopië te evalueer, die beste basters vir kommersiële produksie te selekteer, verskillende statistiese procedures vir die ontlending van G x E interaksies oor nege omgewings te vergelyk en teelstrategië vir die vrystelling van aangepaste genotipes te bepaal. Sewentien experimentele mieliebasters insluitende ‘n standaard cultivar is in die midhooglande van Ethiopië vir ‘n periode van drie jaar (2004 tot 2006) oor drie lokaliteite vir graanopbrengs geevalueer. Die genotipes is in ‘n gerandomiseede blokontwerp aangeplant. G x E interaksie en variansiekomponente is m.b.v. ‘n faktoriaalontlending bereken. Stabilititeitsparameters is m.b.v. verskillend parametriese en nie-parametriese metodes bereken,terwyl ‘n trosontlending uitgevoer is om die omgewings te klassifiseer. Die rekenaarprogramme, Agrobase Generation II (Agronomix, 2008), SAS (SAS Institute Inc., 2003) en NCSS 2004 (Hintze,2001) is gebruik om die verskillende ontledings uit te voer. Die gemiddelde kwadrate vir G x E interaksie was betekenisvol vir opbrengs asook die variasie tussen genotipes(G). Die lokaliteit (L) en Lokaliteit x Jaar (L x J) interaksie het die grootste varinsiekomponente vir graanopbrengs. Dit is ‘n aanduiding van die groot verskille tussen toetslokaliteite wat die gevolg is van jaar tot jaar fluktuasies in reënval. Die eksperimentele mieliebaster PR1 (gemiddelde opbrengs= 7.14 t ha -1) het die hoogste opbrengs gehad, gevolg deur PR13 (6.77 t ha -1). Die resultate toon die potensiaal van die basters vir moontlike vrystelling en kommersiële produksie. Hoogsbetekenivalle korrelasies (P < 0.01) is tussen Eberhart en Russell se afwyking van die regressie (S2 di), Wricke se Ecovalence (Wi), Shukla ( ) 2 σ i se stabiliteitsvariansie en AMMI se stabiliteitswaarde (ASV) gevind. Die gemiddelde opbrengs en Lin en Binn se cultivar superieur prestasie het ‘n groot mate van ooreenstemming getoon maar geen korrelasie getoon met die res van die stabiliteitsparameters. Die nie-parametriese meting van Nassar en Hühn se absolute rangverskille S(1) en rangvariansies S(2) was betekenisvol (P ≤0.05) met ASV gekorreleer, alhoewel dit nie betekenisvol met die res van die parametriese metodes gekorreleer was. Die verskillende stabiliteitsparameters toon dat die basters PR1, PR13, en BH540 die stabielste is in meer gunstige omgewings terwyl die basters SE21 en SE22 die stabielste is in omgewings waar lae opbrengste geld. Aangesien ASV hoë korrelasies toon met beide parametriese en nie-parametriese metings en die gemiddelde opbrengs, word aanbeveel dat ASV as ‘n stabiliteitsparameter gebruik word om stabiele genotipes in multi-omgewings te identifiseer. Die variansie-ontleding vir die AMMI model toon hoogsbetekenisvolle verskille tussen genotipes en omgewings as hoofeffkte asook betekenisvolle G x E interaksie effekte. Die eerste twee interaksie hoofkompenente (IPCA) van die AMMI model het onderskeidelik tussen 34% en 56% van die totale G x E interaksie som van kwadrate vir graanopbrengs verklaar.Die AMMI biplot het die genotipes PR1, SE4, PR2,PR3,BH540 en PR13 as goed aangepas in meer gunstige omgewings geklassifiseer. Die hieragale tros-ontleding gebaseer op die ongeweegde paar groeperingsmetode (UPGMA) het die genotipes in vyf en die omgewings in drie groepe geklassifiseer. Die resultate van die studie oor die optimum allokasie van lokaliteit en jare, toon dat twee tot drie herhalings, drie tot vyf lokaliteite en drie tot vier jaar van toetsing voldoende inligting verskaf vir die akkurate bepaling van opbrengs. Laasgenoemde inligting sal daartoe bydrae om proefkoste te minimiseer en meer akkurate data vir vrystellingsbesluite in Etiopiese toestande te verskaf. Die navorsing toon verder dat ‘n vermeerdering in lokaliteite en jare ‘n groter bydrae lewer tot die akkuraatheid van data in vergelyking met ‘n toename in herhalings.
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectDissertation (M.Sc.Agric. (Plant Sciences: Plant Breeding))--University of the Free State, 2009en_ZA
dc.subjectGenotype-environment interactionen_ZA
dc.subjectCorn -- Geneticsen_ZA
dc.subjectCorn -- Breeding -- Ethiopiaen_ZA
dc.titleGenotype by environment interaction and yield stability of maize hybrids evaluated in Ethiopiaen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record