Typescript. / Thesis (Ph. D.)--University of Hawaii, 1967. / Bibliography: leaves [105]-110. / viii, 110 l illus., tables

Thesis (MSc (FABI))--University of Pretoria, 2008. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Inaug.-diss.--Kiel. / Lebenslauf.

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

Thesis (PhD.(Plant Pathology))--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

The protein encoded by the Nonexpressor of pathogenesis-related gene 1 (NPR1) also referred to as Non inducible immunitiy 1 (NIM1) or Salicylic acid insensitive 1 (SAI1) is a co-transcriptional regulator. The NPR1 gene plays a pivotal role in conferring broad spectrum resistant to plants. Elicitors like salicylic acid and pathogens coupled with the accumulation of reactive oxygen species influence its activation in the cytoplasm. The downstream activity of the NPR1 gene necessitates its translocation to the nucleus and an interaction with other transcription factors with a ‘TGAC’ core sequence for the induction of Pathogenesis-related genes. In this study I identified and isolated homologues of genes encoding the NPR1 protein in banana (Musa sp.). Southern blot analysis revealed the possible existence of more than one Musa NPR1 gene in four different banana cultivars. Furthermore, two banana NPR1 gene fragments designated (MNPR1A and MNPR1B) were isolated and their full lengths recovered and deposited in the gene bank. A preliminary phylogenetic analysis of Musa NPR1 revealed that the two newly isolated banana genes grouped closely with other monocot NPR1 genes. The two identified MNPR1-sequences differed greatly in their expression profile using quantitative real time polymerase chain reaction following either salicylic acid or methyl jasmonate treatment or treatment with Fusarium oxysporum Schlecht f. sp. cubense (Smith) Snyd. MNPR1A was expressed after Fusarium treatment with higher and earlier expression in the Fusarium-tolerant banana cultivar GCTCV-218 than in the Fusarium-susceptible banana cultivar Grand Naine. In comparison, MNPR1B was highly responsive to salicylic acid, but not to methyl jasmonate treatment, in both the tolerant banana cultivar GCTCV-218 and the susceptible banana cultivar Grand Naine. Expression of the MNPR1 genes correlated to Pathogenesis-related gene expression known to be involved in fungal resistance. It was found as a new result in this study that reduced sensitivity to Fusarium in GCTCV-218 might be partially attributed to the higher and an earlier expression of both MNPR1A and Pathogenesis-related-1 genes in this cultivar after Fusarium treatment. / Dissertation (MSc)--University of Pretoria, 2009. / Plant Science / unrestricted

Inaug.-diss.--Kiel. / Lebenslauf.

Bananas are climacteric fruits and show climacteric patterns with respect to both their ethylene production and respiration rates during the ripening process. Treatment with ethylene accelerated the ripening process, evidenced by colour changes. Chlorophyllase apparently synthesised chlorophyll in the 0.2 kGy irradiated fruit during the post-climacteric period. Gamma irradiation of green bananas with doses of 0.4 kGy or greater resulted in extensive tissue damage, undesirable colour development, and drastic changes in respiration and ethylene production. Irradiation at 0.2 kGy, did however, effectively delay ripening (without causing any phytotoxicity) of the fruit apparently by decreasing its sensitivity to its own endogenous ethylene for a period up to 28 days when kept at room temperature, provided that the relative humidity was maintained at 75 % to prevent desiccation. Irradiation at this dose did not prevent the onset of ripening when subjected to high concentrations of exogenous ethylene. Ultrastructurally total cell collapse due to cell wall, middle lamella and membrane damage was evident at doses of 0.4, 0.6 and 1.0 kGy. Irradiation with a dose of 0.2 kGy did not cause cell wall softening and membrane breakdown and thus provided a banana fruit of excellent postharvest quality with respect to ultrastructural features. Glucose and fructose occurred probably directly from sucrose that may not accumulate because it is transient after the banana fruit is harvested. The accumulation of sucrose glucose and fructose was not stimulated by ethylene in non-irradiated and irradiated fruit. These results indicate a clear temporal separation between those biochemical processes that appear to be stimulated by ethylene (respiration, fruit softening and colour change) from those that are not (sugars). Pectin methyl esterase resulted in the demethylation of pectin-like material in the cell walls of ripening bananas. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1991.

A field experiment was conducted at Inselele, KwaZulu-Natal South Coast, South Africa, in 1999/2000, to assess the influence of shading as related to varying levels of incident solar irradiance as well as microclimatic variations on banana (Musa spp) growth, phenology trends, morphology and productivity. The trial was established in August 1999 on a ratoon plantation. The experimental site, 0.655 ha in extent, comprised of three replications with four treatments having varying levels of incident solar irradiance levels of 100 %, 70 %, 40 % and 20 % under a planting density of 1666 plants ha. The irradiance levels were derived from black shade cloth, erected 1 m above the banana canopy level. Banana plantations have vegetation that does not completely cover the underlying ground surface. For such a canopy, there are basically two distinct and interacting surface components, the overstorey/canopy and the understorey/soil. Independent investigations and measurements of the solar energy fluxes for each of these two components forms a vital step to comprehend the factors that control the overhead energy fluxes in the plantation. In this study, evaluation of flux components in the understorey of the canopy using plastic microlysimeters was conducted. Considering normal variations in field measurements, the agreement and consistency among the different measurements with previous findings was adequate. Microlysimeter measurements of daytime soil evaporation were generally less than 1 mm, with an average of 0.45 mm. The study did not include flux measurement at the two level approach (Bowen ratio and Eddy correlation methods) which could have been compared with the single level approach and microlysimeter results. Two methods of deriving/measurement of energy fluxes were used and the differences between them are discussed. A reassessment of the microlysimeter technique is suggested. For the understorey, the sum of sensible and latent heat fluxes derived from spreadsheet computation was equal to the available energy. Mean soil temperatures at a depth of 20 to 60 mm ranged between 13 and 16 degrees C. This study illustrated that energy flux measurement and interpretation in within the experimental area. Good agreement was found in the patterns of wind speed profile measurements, with the 1.5 m profile depicting a mean difference of 52 % compared to the 3 m profile between day of year (DOY) 230 and 248 inclusive. This suggested that wind speed attenuation was strongly correlated to increment in height within the plantation due to canopy roughness. Differential canopy temperatures (measured with infrared thermometry) were more sensitive to the vapour pressure deficit than to wind speed. The most dense shade affected banana productivity indicated by a bunch weight of 22.69 and 33.65 kg under the 20 % and 100% irradiance treatments respectively. The bunch mass reduction was 32 %. Flowering dates were delayed by 8 days, 13 days and 21 days with incident irradiances of 70 %, 40 % and 20 % of the unshaded control (lOO % irradiance), respectively. The phenological responses in this study appear to be a result ofa contribution or interaction of both seasonal responses and shading treatments and this is further evidenced by the high levels of correlation (98.4%) reported between these two variables. Shading resulted in diminished leaf emergence rates (LER), pseudostem circumference and pseudostem height. However, just before flowering, no significant differences were observed in the pseudostem circumferences. There was a progressive increment in pseudostem height for all the treatments, with the 20 % irradiance treatment depicting the least heights registered compared to the rest of the treatments. Evident seasonal differences were registered in the LER and emergence to harvest (EH) interval. Comparison of LER and mean air temperature trends revealed a similar curve pattern and depicted a highly positive correlation of90.4%. The highest LER of3.8 was recorded in the month of January at a peak mean monthly air temperature of24.3°C while the lowest LER of 1.2 was registered in July which had the lowest mean air temperature of 14.7 cc. The EH intervals measured between September and December flowering varied from 125 days to 112 days respectively before harvest yet the April to May flowering had an EH duration of186 to 195 days respectively. The strong seasonal influence on phenological responses is further confirmed by these EH trends. Reductions in LAI observed with time were principally due to leaf senescence. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Graduation date: 1948