Doctoral Degrees (Plant Sciences)

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Browsing Doctoral Degrees (Plant Sciences) by Subject "Agronomical"

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    Characterisation and diallel analysis of commercially planted cotton (Gossypium hirsutum L.) germplasm in Tanzania
    (University of the Free State, 2005-11) Lukonge, Everina Paul; Labuschagne, M. T.; Herselman, L.
    English: 1. Thirty cotton varieties were studied. Seven parents generated 21 F1 diallel progenies. The main objective was to evaluate genotypes through oil content, fatty acids, morphological and molecular characteristics. Statistical procedures were performed with Agrobase, NCSS and NTYSS computer programmes. Correlation, heterosis, heritability, G x E interaction and stability values were obtained. Stability across four environments was analysed by five stability measures, that of Shukla, Wricke, Lin and Binns, Eberhart and Russell and the AMMI analysis. 2. Significant differences were observed for oil and fatty acids content. Oil content results revealed an average of 20.23%. The ratio for polyunsaturated:saturated fatty acid was 2:1 and for unsaturated:saturated 3:1. The predominant fatty acids were linoleic, palmitic, oleic, stearic, myristic, palmitoleic, arachidic and behenic. Palmitic fatty acid was high while oleic and stearic fatty acids were low for almost all varieties studied. Oil and fatty acid content were significantly influenced by the environment. CIM 70 and Cyto 12/74 can be selected as parents for increased oleic and stearic fatty acid and Stoneville 506 as a parent for reduced palmitic fatty acid, increased oleic, stearic and linolenic fatty acids in hybridisation. 3. ANOVA results indicated significant differences between varieties for all agronomical characteristics studied, where NTA 93-21 and NTA 93-15 were the best performers almost for all characteristics. Genetic distances for morphological (qualitative characteristics) analysis ranged from 0.18 to 0.80. Two major groups, one including many varieties from Africa and the other including varieties from the USA, were revealed. 4. AFLP analysis showed high genetic similarities (0.85 to 0.98). Varieties were distinguished according to pedigree and origin. The increased genetic similarity observed, indicates the need for the introduction of more diverse cotton material. Comparison of agronomical and AFLP markers for determining genetic diversity indicated that genetic similarities between varieties were low for agronomical compared to AFLP markers. The correlation coefficient between AFLP analysis and agronomical genetic similarities was not significant, 5. Highly significant differences between genotypes over environments were observed and NTA 93-21 crosses outperformed the seven parents for almost all characteristics. The parent Okra leaf performed poorly for many characteristics. Trial sites Ukiriguru followed by Kanziga were high yielding environments. 6. Combining ability analysis results indicated significant variation in GCA estimates among parents for different characteristics. Genotypes having high positive GCA estimates for yield components exhibited negative GCA estimates for fibre quality, excluding NTA 93-21. Some combinations indicated positive and significant SCA effects for seedcotton, boll weight, GOT and lint yield. The GCA/SCA ratios for most of the studied characteristics were larger than one. 7. Correlation among characteristics indicated highly significant positive and negative correlations. The observed high and significant GCA and SCA effects for those characteristics are promising for cotton population improvement. Positive heterosis for boll weight was observed for more than 90% of the combinations. Hybrids with high SCA values presented high values of heterosis. Heritability values for the studied characteristics were moderate to high. 8. The combined ANOVA over four environments indicated significant differences between genotypes and locations for all characteristics. The percentage contribution of location to total variation was high compared to genotype variation except for a few characteristics. Highly significant differences of G x E for lint yield and fibre strength were observed. 9. Three stability procedures (Wricke, Shukla and ASV) identified similar stable genotypes. Eberhart and Russell’s procedure, was in harmony with the above three methods but with some divergence. Cultivar superiority measure deviated from the other four measures. Therefore the procedures of Wricke, Shukla and AMMI can be applied for cotton stability studies.