Thesis(PhD(Zoology and Entomology))-University of Pretoria, 2006. / Abstract in English. Includes bibliographical references.

No description available.

The ripening of bananas is a process that needs to take place in accurately controlled conditions to ensure synchronization of all the metabolic processes that are involved with ripening so that the best quality product can be made available to the consumer. Optimal ripening requires the correct ambient room temperature and relative humidity, adequate ventilation and ethylene treatment. Banana ripening occurs at temperatures between 16º-18ºC, with 95% humidity and constant ventilation. Ripening is triggered when the bananas are exposed to ethylene for 24 hours. Fruit that ripens in ideal circumstances has a bright yellow colour, firm soft pulp and strong peel, are sweet tasting and have a pungent aroma. The conditions in the store and ripening rooms, especially temperature, are not always regulated to the optimum and subtropical fruits such as bananas are injured at temperatures below 12ºC. Phase transitions in the membranes, from a liquid-crystalline to a solid gel-like phase, are responsible for chilling injury. Chilling injury delays ripening, but does not noticeably influence the eating quality of the fruit. The bananas are still sweet with a firm soft pulp and strong peel. The aroma production is however reduced by the cold and undesirable colour changes occur. The chilling injured bananas are dull greyyellow in colour with brown or black spots on the peel. The peel sometimes becomes completely brown or black. The quality of the bananas is potentially influenced by this colour change since the consumer judges the fruit on visual appearance. Controlled atmosphere storage and modified atmosphere packaging reduce chilling injury and extends the life of the fruit due to delayed ripening. Chilling injured fruit consequently has less brown or black spots and sometimes even an improved yellow colour. A better quality product can be supplied to the consumer and the temperature control in the storeroom does not need to be 100% accurate. The advantages of these techniques are attributed to the modified atmospheres, namely reduced oxygen and increased carbon dioxide concentrations which influence respiration, ethylene synthesis and action. / Prof. C.S. Whitehead

"November 2002" Includes bibliographyical references (leaves 150-172)

"November 2002" / Includes bibliographyical references (leaves 150-172) / xvii, 172, [53] leaves : ill. (chiefly col.), plates (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2002

Thesis (M. Sc)(Microbiology)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Cavendish bananas are the most important sub-group of all bananas. They includes more than 30% of the global banana production and almost all bananas exported are of the Cavendish type. This sub-group is also an important food source. Most of the fruit is consumed locally, such that only 35% enters the international market. To meet the regular demand for domestic consumption and market supply there must be a reliable production strategy. The technique of tissue culture is a better option than conventional propagation techniques. However. the high incidence of somaclonal variation among plants derived from tissue culture is a problem for commercial producers. Several factors such as genotype, tissue source, duration in culture, and the tissue culture technique employed, cause somaclonal variation. The impact of plant growth regulators on somaclonal variation was studied on Cavendish banana cv. 'Zelig' obtained from African Biotechnologies Ltd., South Africa. In vitro grown plants at the 4th multiplication cycle were supplied for the investigation. The first component of the investigation dealt with the effect of types of plant growth regulators. Combinations of the auxins IAA, IBA and NAA with the cytokinins BA and TDZ were used to culture the plants for ten multiplication cycles. Plants were then randomly selected to collect leaf material for DNA extraction and RAPD analysis. The second aim of this study was to investigate the effect of the cytokinin BA on plantlets subcultured over 5-10 multiplication cycles. The auxin IAA at the concentration of 2 mgl-1 was combined with BA at concentrations of 2.5, 5.0 and 7.5 mgl-1. Plants were analyzed at each level of subculture from the 5th to the 10th cycle for respective cytokinin concentrations. Plants were then randomly selected for the collection of leaf material for DNA extraction and RAPD analysis. DNA was extracted from leaf tissue of in vitro grown plants using a modified CTAB extraction procedure. DNA amplification products were scored for the presence and absence of bands in a particular locus. Results were clustered according to their similarities. The relationship between multiplication rate and variation was assessed using correlation analysis. Results of the investigation showed that treatments with higher multiplication rates produced higher rates of variation. A variation rate of 55% was recorded for treatments containing IAA and BA. A higher rate of variation (72%) was identified in the treatment with IAA (2mgl-1) plus BA (7.5 mgl-1) over 10 cycles. In all cases the dwarf off-type was the most common type of variant obtained, contributing 87.7% of the total amount of variation. The dwarf specific marker (OPJ-041500) reported previously in Williams Cavendish was identified in cv. 'Zelig' in this study. Another band similar in size was amplified by primer OPC-15 and named OPC-151500 . This band consistently appeared in all the normal plants and was absent in all the dwarf types and hence could be used as a dwarf specific marker. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

No description available.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

No description available.