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 Russellâs 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-07272006-134322 |
| Date | 27 July 2006 |
| Creators | Lukonge, Everina Paul |
| Contributors | Dr L Herselman, Prof MT Labuschagne |
| 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-07272006-134322/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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