Biometrical approaches for investigating genetic improvement in wheat breeding in South Africa
dc.contributor.advisor | Labuschagne, M. T. | |
dc.contributor.advisor | Pakendorf, K. W. | |
dc.contributor.author | Boyse, Mardé | |
dc.date.accessioned | 2015-10-14T10:15:23Z | |
dc.date.available | 2015-10-14T10:15:23Z | |
dc.date.copyright | 2014-01-31 | |
dc.date.issued | 2015-10-28 | |
dc.date.submitted | 2014-01-31 | |
dc.description.abstract | English: Wheat is the biggest winter cereal crop in South Africa and the second largest cereal to feed the population of South Africa. The population of South Africa grows with approximately one million people a year. Consistent wheat production is necessary for food security and is therefore of extreme agricultural and economic significance. Future production increases depend on the ability to improve, or at least maintain, the rate of increase to feed the population. The study was undertaken to investigate genetic improvement (genetic advance) in wheat by various statistical methods of analysis. This was done to determine the most suitable procedure to evaluate genetic improvement in the three wheat production areas of South Africa, namely the Western Cape Province, the Free State province and the irrigation areas. The second objective of this study was to demonstrate the trend of yield and the two quality traits [HLM (hectolitre mass) and protein content] over 16 years (1995-2010) by various statistical techniques. The third objective was to compare the AMMI (additive main effects and multiplicative interaction) and the GGE (genotype plus genotype-by-environment interaction) analyses in assessing genotype-by-environment interaction (GEI) for yield and the two quality traits. The fourth objective was to study the relationship among wheat grain yield and the two quality traits by various statistical techniques. Linear regression (TRET) and various variance component methods were investigated to determine genetic advance. The recommended method of determining genetic advance in this study is TRET. In the Western Cape elite trials TRET predicted a genetic advance of 1% per year and genetic advance estimated at 1% genetic improvement for protein content in the cultivar trials. No significant trend was observed in the elite trials of the Free State with TRET. Yield showed 0.5% and 0.6% per year improvement for the two planting dates of the eastern cultivar trials of Free State. A yield improvement of 0.3% per year improvement for the two planting dates of the central cultivar trials of Free State was determined. A genetic advance for yield of 0.7% per year was found in the warm region of the elite irrigation trials and 9% yield improvement per year for the first planting date of the eastern region of the cultivar irrigation trials. A negative trend was observed for the second planting date of eastern region of both elite and cultivar irrigation trials. The effects of GEI on yield and quality traits were studied by comparing the AMMI and GGE analyses. These methods portrayed similar results. An advantage of these techniques is their complementary nature. Although both models portray GEI in various biplots, the AMMI provides statistical evidence to the visual presentation of the GGE biplots. Pearson product moment correlation matrix provided a linear relationship among the variables studied. Principal component analysis (PCA), cluster analysis (CA) and discriminant analysis (DA) offered auxiliary information on the relationship among the factors (e.g. genotypes, years, localities and/or environments) and the variables. DA was not able to indicate direction of genetic improvement in either of the three production areas in this study. | en_ZA |
dc.description.abstract | Afrikaans: Koring is die grootste winter graangewas in Suid-Afrika en die tweede grootste graangewas om die mense van Suid-Afrika te voed. Die bevolking van Suid-Afrika vermeerder met naastenby ‘n miljoen mense per jaar. Volhoubare koringproduksie is noodsaaklik om voedselsekerheid te verskaf en is daarom van uiters hoë landbou en ekonomiese waarde. Toekomstige opbrengsvermeerdering is afhanklik van die verbetering in potensiaal en ten minste instandhouding van die opbrengs om in die kosbehoeftes van die bevolking te voorsien. Hierdie studie is onderneem om die genetiese vordering in koring deur verskeie statistiese metodes te ondersoek. Die drie koringproduksie streke van Suid-Afrika, naamlik die Wes-Kaap provinsie, die Vrystaat provinsie en die besproeiingsgebiede is ondersoek om aan hierdie doelwit te voldoen. Die tweede doelwit van die studie was om die tendens in opbrengs en die twee kwaliteitsveranderlikes, hektolitermassa (HLM) en proteïeninhoud oor 16 jaar (1995-2010) met behulp van verskeie statistiese tegnieke te ondersoek. Die derde doelwit was om vir elkeen van die drie veranderlikes die AMMI (additiewe hoofeffek en multiplikatiewe interaksie) en GGE (genotipe plus genotipe-omgewingswisselwerking) modelle wat genotipe-by-omgewingsinteraksie (GEI) beskryf, te vergelyk. Die vierde doelwit was om die verwantskap tussen die koringopbrengs en die twee kwaliteitseienskappe met behulp van verskeie statistiese tegnieke te beskryf. Metodes soos liniêre regressie (TRET) en verskeie variansie komponentmetodes is ondersoek in die bepaling van genetiese vordering. Die voorgestelde metode om genetiese vordering te bepaal is TRET. In beide streke in die Wes-Kaap toon TRET genetiese vordering van 1% per jaar vir opbrengs in die elite proewe. In die cultivar proewe van hierdie streke kon TRET geen vordering in opbrengs toon nie, maar wel 1% vordering per jaar vir proteïeninhoud. Geen betekenisvolle tendens kon in die elite proewe van enige van die Vrystaat streke bepaal word nie. In die oostelike streek van die cultivarproewe is daar onderskeidelik 0.5% en 0.6% per jaar genetiese vordering in opbrengs van die twee plantdatums getoon. ‘n Vordering van 0.3% in opbrengs is in die sentrale streek van die Vrystaat bepaal. Met behulp van TRET is genetiese vordering in opbrengs van 0.7% per jaar in die warm gedeeltes van die elite besproeiïngsproewe en 9% vordering per jaar vir die eerste plantdatum van die oostelike cultivar besproeiïngsproewe bepaal. ‘n Negatiewe tendens vir die tweede plantdatum van beide die elite en cultivar proewe van die oostelike besproeiïngsgebied is gevind. Die effek van genotipe-omgewingswisselwerking vir opbrengs en die kwaliteitseienskappe is bestudeer en vergelyk met behulp van die AMMI en GGE. Hierdie metodes verskaf soortgelyke antwoorde. Die voordeel van hierdie tegnieke is hulle aanvullende aard. Alhoewel beide metodes genotipe-omgewingswisselwerking in verskeie ”biplots” weergee, verskaf die AMMI statistiese bewyse vir die visuele voorstelling van die GGE “biplots”. Pearson produk-moment korrelasiekoeffisiënt verskaf ‘n liniêre verwantskap tussen die veranderlikes. Hoofkomponentanalise (PCA), trosanalise en diskriminantanalise (DA) verskaf bykomende inligting tot die verwantskap tussen die faktore (o.a. genotipes, jare, lokaliteite en/of omgewings) en die veranderlikes. Diskriminantanalise kon nie die rigting van genetiese vordering aandui nie. | af |
dc.identifier.uri | http://hdl.handle.net/11660/1376 | |
dc.language.iso | en | en_ZA |
dc.publisher | University of the Free State | en_ZA |
dc.rights.holder | University of the Free State | en_ZA |
dc.subject | Wheat -- Breeding -- South Africa | en_ZA |
dc.subject | Wheat -- Genetics -- South Africa | en_ZA |
dc.subject | Cluster analysis | en_ZA |
dc.subject | Genotype-by-environment interaction | en_ZA |
dc.subject | Variance component methods | en_ZA |
dc.subject | Linear regression | en_ZA |
dc.subject | Genetic improvement | en_ZA |
dc.subject | Genetic advance | en_ZA |
dc.subject | Thesis (Ph.D. (Plant Sciences: Plant Breeding))--University of the Free State, 2014 | en_ZA |
dc.title | Biometrical approaches for investigating genetic improvement in wheat breeding in South Africa | en_ZA |
dc.type | Thesis | en_ZA |