Masters Degrees (Horticultural Science)

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Some ecophysiological aspects of cashew (Anacardium occidentale L) with emphasis on possible flower manipulation in Maputaland.
(1994) Roe, Denis John.; Wolstenholme, B. Nigel.
There has been interest in developing a cashew industry in Maputaland, the far north-eastern corner of Natal/KwaZulu. Flowering and fruit development coincide with a rainy period, with accompanying serious flower diseases (Oidium anacardii and Colletotrichum gloeosporioides). Glasshouse studies were carried out at Pietermaritzburg, concurrently with field trials in Maputaland, in an attempt to manipulate flowering and growth of cashew trees. Two glasshouse trial were carried out. A factorial design with treatments 0, 3, 6 and 9 weeks of low temperatures (24°C day/9°C nights)(factor A) and 0, 3, 6 and 9 weeks of water deficit (Factor B) was used, with both factors in all combinations. During the second season the durations were increased to 0, 4, 8 and 12 weeks for both factors. No flowering occurred in this trial. Tree growth was not affected significantly by drought and/or cold duration. Temperature appeared to be the dominant factor at low temperatures, stomatal conductance and transpiration being suppressed by cold regardless of soil water potential. At more optimum temperatures for growth, stomatal conductance was dependent on soil water potential (r² = 0.756). Starch levels in the roots, dry matter production in the leaves, roots and stems, as well as leaf area were decreased significantly (P≤0.01) with increasing low temperature duration. Another glasshouse trial to test the effects of foliar urea at concentrations of 0, 1, 2, 4 and 8 g urea 100 l⁻¹, applied once, twice or thrice at fortnightly intervals was undertaken. The treatments were applied in late autumn/early winter of 1990 and 1991. Tree growth and flowering were monitored, and starch and leaf NH₃/NH₄⁺ analyses carried out. The highest urea concentration (8%) resulted in leaf scorch and abscission, extremely low stem diameter growth rates, and was too high for glasshouse trees. The starch contents of the 8% urea treatment were depleted significantly (P≤0.01) more than the other concentrations. The other urea treatments resulted in vigorous growth and high dry matter production. There were no significant effects of the number of sprays on cashew growth. Only seven trees flowered, and therefore no definite conclusions could be drawn regarding urea effects on flowering. Most hermaphrodite flowers (max. 76.8% hermaphrodite) opened soon after first anthesis of a panicle, and all terminal flowers of panicle branches were hermaphrodite. Flowers generally opened basipetally in a panicle, starting with hermaphrodite flowers and with progressively more male flowers. Urea sprays resulted in NH₃/NH₄⁺ build-up in the leaves, concentrations in flowering trees ranging from 100 to 700 μg g⁻¹ DM for approximately a month. A field trial at was carried out at Makatini Research Station to determine the effects of timing of a two month winter drought period on flowering and growth. An observational trial to determine the effects of girdling on growth and flowering was incorporated in the border rows of the irrigation trial. The trial tested five treatments (no irrigation during May and June, June and July, July and August, August and September, and a control treatment which received irrigation throughout Winter). Mean monthly temperatures were below 20°C, and mean minimum temperatures below 15°C for the 5 winter months during treatment application. There were no significant differences in tree growth, flowering, flushing, or yields between drought stressed treatments and control, indicating that, under the conditions at Makatini, autumn and winter temperature was the overriding factor controlling initial flower induction. Flowering occurred from early October (when mean temperatures exceeded 23 to 24°C) to late April (7 months - a prolonged flowering period), when mean monthly temperatures dropped below 23 to 24°C. Girdling of cashew trees in March and May, using girdle widths of 1, 5 and 10 mm was not successful in improving flowering and yields under the conditions of the trial. A field trial was carried out at Mosi Estate in Maputaland to test the following chemicals as tree and/or flower manipulators: foliar applied ethephon (50,100,200,500,2000 mg l⁻¹), KNO₃ (1 %, 2%, 4%), urea (1 %, 2%, 4%) and paciobutrazol (500, 1000, 2000 mg l⁻¹). A phenological model for cashew in Maputaland showed a dormant period during winter, followed by a generative flush, from which panicles and flowers were produced (peak November-January). The harvest period peaked in February and March. A strong post-harvest flush preceded the winter dormant period. Trunk starch levels were at their highest after the dormant winter period, and at their lowest following the harvest. Ethephon at high concentrations (500 and 2000 mg l⁻¹) resulted in excessive leaf drop, disturbed the root shoot balance and normal phenological patterns, and gave poor yields. The best ethephon concentrations were 100 to 200 mg l⁻¹. KNO₃had no significant effect on tree growth, flushing, flowering or yields when compared to control trees. Urea at 2% concentration gave a significant increase (P≤0.05) in flushing and simultaneous decrease in flowering. Paclobutrazol at 500 to 2000 mg l⁻¹ resulted in significantly lower growth rates, and early panicle production. The mean yields of all paclobutrazol treated treatments were higher than controls, despite a hail storm which damaged the flowers. From results of this trial, the use of these chemicals to improve yields and manipulate flowering may not be economically justified. The most promising chemical for further research was paclobutrazol.
Some aspects of cold storage of 'Fuerte' avocados (Persea americana Mill.) grown in the Natal midlands.
(1995) Donkin, Derek John.; Wolstenholme, B. Nigel.; Cutting, Jonathan Garth Melville.
The South African avocado industry is largely export orientated and export by sea to European markets necessitates cold storage for up to 4 weeks at temperatures around 5.5°C. Avocado fruit is subject to chilling injury which is manifested as mesocarp discolouration, and pitting and blackening of the rind. Of the South African cultivars exported, 'Fuerte' is the most susceptible to chilling injury, and accounts for > 50 % of avocado exports. A number of temperature regimes where temperature was reduced in a step-wise fashion from 8.5 or 7.5°C to 4.5 or 5.5°C during 3 to 5 weeks of storage were tested weekly throughout the 1993 and 1994 'Fuerte' harvesting seasons in the Natal Midlands (a cool mesic subtropical area), in attempt to find cold storage temperature regimes which would minimise chilling injury. No definite trends with regard to certain temperature regimes resulting in fruit with less chilling injury were evident. Overall, stepped down temperature regimes produced fruit of quality no better than storage for 5.5°C for 4 weeks. There was no significant difference in concentration of total phenolics in 'Fuerte' fruit mesocarp throughout the 1994 harvesting season (P < 0.05). Levels of ethylene evolution during 4 weeks of storage at 7.5 and 5.5°C ranged from 0 to 5 µl.kg(-l).h(-l), and peaked at 109 and 75 µl.kg(-l).h(-1) in fruit stored at 7.5 and 5.5°C respectively at room temperature on removal from cold storage. Rapid moisture removal from 'Fuerte' fruit after harvest and before cold storage by placing the fruit in glass jars to which a suction of -75 kPa was applied, resulted in increased susceptibility to external chilling injury, the severity of which was proportional to the amount of moisture removed from the fruit. Pre-storage heat treatments with a view to decreasing sensitivity of fruit to cold storage were carried out on 'Fuerte' fruit. Dry heat and warm water baths at temperatures of 36 to 40°C caused rind blackening of varying severity, depending on temperature and duration. Vapour heat treatments at temperatures of 36 to 48°C for 10 min to 48 h also caused rind blackening, with the exception of 10 min at 48°C and 1.5 and 3 h at 40°C which produced fruit of higher overall quality after 4 weeks of cold storage at 3.5°C than fruit not heat treated. These treatments however, could not be repeated in 1994 to confirm the results obtained as the harvesting season was over by the time the trial was completed.
A prediction model to determine the cross-pollination ability of Citrus spp.
(1995) Barry, Graham H.; Wolstenholme, B. Nigel.; De Lange, Hannes.
Due to a greater emphasis having been placed on seedlessness by citrus consumers, a need developed in the southern African citrus industry to avoid unwanted cross-pollination and hence seediness. There was a paucity of knowledge upon which to base sound decisions in order to ensure optimal orchard layout to achieve the objective of the production of seedless or "commercially seedless" fruit. In vitro pollen viability of all locally available citrus cultivars/selections was determined and pollen of cultivars with strong and weak pollination potential were used for in vivo pollen tube growth and seed content studies of 'Nules Clementine' mandarin and 'Delta Valencia' orange. Data from the in vitro assays were rated and categorized into 'pollen germination potential categories', while the relationship between these categories and seed content of 'Nules Clementine' was determined by regression analysis. The development of the 'pollen germination potential categories' provides an additional facet to the evaluation and development of new citrus cultivars, providing a means to determine the pollination potential at an early stage of that cultivar's development. Citrus cultivars with a pollen germination percentage exceeding 2 % are likely to set too many seeds for the export of 'Nules Clementine' mandarins according to South African export requirements. In addition to the two previously known pollen sterile cultivars, viz. 'Navel' orange and 'Satsuma' mandarin, 'Star Ruby' grapefruit and 'Delta Valencia' orange have been identified in this study as pollen sterile cultivars that can be used as buffers to avoid cross-pollination between two pollen fertile cultivars. Furthermore, 'Delta Valencia' is also ovule sterile. An initial model is presented whereby the seed content of cross-pollinated 'Nules Clementine' fruit can be predicted (r2 = 0.9192) by determining the in vitro pollen viability of the cross-pollinating cultivar/selection and be calculated as follows: 2.619 x pollen germination category of compatible cultivars - 2.449.
Nutrition of containerised pine (Pinus patula Schlecht. et Cham.) seedlings grown in pine bark.
(1996) Jarvel, Leanne.; Smith, Irwin Elcoate.; Wolstenholme, B. Nigel.
Increasing demands for timber and timber products have resulted in the rapid expansion of containerised forestry seedling production. The lack of available information on pine seedling fertilization has forced nurserymen to use overseas recommendations which are based on peat and vermiculite as growing media, and not composted pine bark. Six fertilization trials were conducted in plastic enclosed "tunnels" to provide fertilization recommendations and optimum foliar nutrient concentrations for P. patula seedlings grown in composted pine bark. It was concluded that pre-enrichment of the pine bark should include micronutrients, preferably in the form of Micromax®, a soluble micronutrient fertilizer, at 1000 g.m(-3). Pre-enrichment with lime was unnecessary for pine bark media since pine bark contains sufficient Ca and Mg. At an unlimed pH of 4.5, the availability of micronutrients was adequate for pine seedling growth. The addition of an N-P-K fertilizer and scheduling of nutrients, to correlate with seedling growth stage, are essential for maximum pine seedling production. Slow release forms (SRF) of N-P-K fertilizers were not beneficial, although their use may be warranted when the cost of SRF is similar to that of conventional fertilizers. Nitrogen in the form of NH(4+)-N at 80 mg.l(-1) was shown to produce the best quality P. patula seedlings. The addition of Si, in the form of pre-enriched silicate slags and si nutrient solutions, reputed to improve growth by decreasing cuticular water loss and increasing plant rigidity, provided no added advantage to pine seedling growth under the trial conditions. It was concluded that individual nurseries should formulate a nutritional programme for their own situation, based on these guidelines. Care should be taken when extrapolating these results to other substrates and it is recommended that the medium be analysed before a nutritional programme is decided on.
Bowen ratio and surface temperature techniques for measuring evaporation from cabbages.
(1997) Lukangu, Gastao.; Savage, Michael John.; Johnston, M. A.
Good irrigation water management requires accurate, automated, non-destructive and simple techniques to measure crop water consumption. The actual evaporation from a cabbage crop was measured using the Bowen ratio energy balance technique (BREB), the surface temperature technique and the Penman-monteith method. All models used the shortened energy balance equation to estimate latent heat in which the advected energy is assumed to be negligible. Four irrigations were applied and 17 rainfall events were recorded during the experiment. The soil at the experimental field was a clay loam. An attempt to detect and reduce measurement error that could result from using inaccurate sensors was performed by calibrating the sensors. Data from inaccurate sensors were not used to compute the latent heat. Error and sensitivity analyse were performed, and the integrity of the weather data using the estimates of weather data from an appropriate model were checked. In addition, a comparative study showed that, for daily totals, there was a very small error in the latent heat calculations when fixed "constants" (density of air, specific heat capacity of air, psychrometric constant, slope of the saturation water vapour pressure vs temperature relationship and specific heat capacity of soil) were used instead of calculated ones. The Bowen ratio (β), a fundamental input of the BREB technique, was estimated accepting the Similarity Principle and excluding nighttime data. However, an error in β was also observed during the daytime measurement of the profiles entities because the sensors were wet and the stability condition was different from neutral conditions under which the Similarity Principle could not be observed. Negative values of β were observed when there were strong winds advecting sensible heat into the field under study. Data were rejected during mornings, and during strong advection periods. Data were also rejected when the sensors were wet because of rain or irrigation. In this experiment, only 35 % of data were valid for determining latent and sensible heat estimated using the BREB technique. Comparative analysis showed that the BREB technique overestimated the latent heat by 17 % compared to the Penman-Monteith method. However, both the Penman-Monteith method and BREB technique could not be trusted because of the presence of advection, a component of the energy balance equation normally assumed to be negligible. Either the surface to air temperature differential or the aerodynamic resistance, or both, were the source of overestimation of latent heat using the surface temperature technique. The surface to air temperature differential was large in magnitude when there were high wind speeds and drier conditions in the upwind field . It was small with lighter wind speeds and wetter surface conditions. An error of less than 5 % was attributed to the use of fixed air density and specific heat capacity and acceptance of 2 % and 20 % error in measuring the net irradiance and soil heat flux density, respectively. A comparative study showed that the surface temperature latent heat was overestimated in relation to the Penman-Monteith and BREB latent heat. Generally, the technique has been reported to overestimate evaporation, although to a lesser extent than the 57 % error reported in this experiment when compared to the BREB technique. An analysis of the energy balance closure, taking the Penman-Monteith and BREB as standards, suggested that the surface temperature technique overestimated the consumption of sensible heat from the air. This observation was also confirmed when the eddy correlation technique was used to compare sensible heat estimated using the surface temperature technique. The effect of placement height of air temperature sensors suggested that the consumption of sensible heat would be overestimated if the sensor was placed far from the crop surface. This overestimation in consumption of sensible heat resulted in an overestimation of latent heat. Irrigation water management was analysed using the crop water stress index (CWSI). The CWSI was calculated using the actual to potential evaporation ratio estimated using the Penman-Monteith method and the surface temperature techniques. The estimated and measured actual surface to air temperature differential, and the estimated potential and non-transpiring surface to air temperature differential were also used to estimate the CWSI using the Penman-Monteith method, the surface temperature technique and empirical method. The estimates of the CWSI using these techniques were inaccurate because of the poor correlation between the surface to air temperature differential and the water vapour pressure deficit (or water vapour pressure deficit and net irradiance). However, use of the CWSI estimated using the actual to potential evaporation ratio (CWSI = 1 - λ(a)/ λE(p) compared well to the standard CWSI determined using the Penman-Monteith approach. The actual canopy resistance was estimated using an empirical equation based on the potential canopy resistance, solar irradiance, soil water content and the shelter factor. A value of 50 s m(-1) was estimated for potential (minimum) canopy resistance of the cabbage crop. The soil water content was poorly correlated to CWSI, while the canopy resistance was well correlated. Comparative analysis showed that the estimated soil water content using the soil water balance equation was underestimated in relation to the soil water content measured using the ThetaProbe (frequency domain reflectometry technique) when the evaporation component was overestimated, and vice versa. Soil water content was underestimated throughout the experiment when evaporation from the surface temperature technique was used. There was an underestimation of soil water content in the early stages and overestimation in later stages of the experiment when the BREB and Penman-Monteith evaporation were used. Use of the estimated soil water content using the soil water balance with the overestimated evaporation would result in an early date of irrigation application, an unnecessarily large irrigation amount and frequent irrigations. More research is needed to find the cause of overestimation of evaporation using the surface temperature technique. The robustness of the equipment allowed a long period of measurement without frequent maintenance, as was required when using the BREB technique. The technique can monitor evaporation and irrigation management aspects at a regional scale. A combination of the Penman-Monteith, surface temperature and empirical method can assist the estimation of the crop water requirement by determining the CWSI. Future research would focus on quantification of sensible and latent heat advection, and analysis of additional resistances to water vapour flow from the surface to the atmosphere. The equipment for the BREB should be refined so that it measures actual latent heat under adverse weather conditions for a protracted period. A precise use of the soil water balance equation for water management should take into consideration runoff, vertical flow of soil water through a profile, intercepted water on plant surfaces and an accurately determined evaporation.
Banana (Musa AAA; Cavendish sub-group) cultivar/density trials in three bioclimatic groups on the north coast of KwaZulu-Natal.
(1997) Lagerwall, Gary Brian.; Wolstenholme, B. Nigel.
The North Coast of KwaZulu-Natal is a relatively new banana production area, for which there is an absence of local norms, specifically for choice of cultivar and population density. Three cooperative split-plot banana cultivar/density trials were established in December 1991, January 1992 and February 1992 on farms at Eshowe, Nkwaleni and Mposa, respectively. These sites represent Phillips' (1973) Bioclimatic Groups 2,10 and 1 respectively, and have widely divergent climatic potential, ranging from cool, to warm, to hot subtropical. Each randomised trial block, 0.92 ha in extent, comprised five replications of five cultivar main plots, each of which was split into three density sub-plots. The five cultivars planted represent those registered at the time of planting, viz. 'Dwarf Cavendish', 'Williams', 'Grand Nain', 'Valery' and 'Chinese Cavendish'. Sub-plots were planted at 1 666, 2 105 and 2 500 plants ha(-1) and tissue culture plants were used to establish all three trials. The field trials were evaluated over three full cropping cycles and culminated in October 1996. Morphological differences such as pseudostem height and circumference, leaf length and width, number of functional leaves at flowering and harvest, as well as phenological differences such as monthly leaf emergence rates, emergence-to-harvest intervals and harvest cycles, were evaluated. The yield component data comprised measurements of bunch mass, number of hands per bunch and number, length and mass of fingers on the third hand. Productivity was expressed as tonnes per hectare per annum (t ha(-1) an(-1). Each cultivar and density treatment was evaluated independently. However, it was the evaluation of the cultivar/density interaction which formed the basis of the recommendations for the three different Bioclimatic Groups. At the relatively cool Eshowe site, 'Williams' proved to be the most productive cultivar (471 ha(-1) an(-1) over all densities. The highest production (49.8 t ha(-1) an(-1) was achieved from a density of 2 500 plants ha(-1), but due to lower costs per hectare, the intermediate density of 2 105 plants ha(-1) generated the highest gross margin. When the cultivar/density interaction was evaluated, the combination producing the highest gross margin was 'Williams' at 2 105 plants ha(-1). This substantiated the independent evaluations and is consequently the recommended combination for Bioclimatic Group 2. However, the faster cycling of 'Chinese Cavendish' could conceivably result in this cultivar outperforming 'Williams' in future ratoons. At the warmer Nkwaleni site, 'Grand Nain' (57.8 t ha(-1) an(-1) proved to be the most productive cultivar. The density of 2 500 plants ha(-1) was the most productive (64 t ha(-1) an(-1) and also generated the highest gross margin. However, the cultivar/density interaction indicated that 'Williams' at 2 500 plants ha(-1), was the highest producing combination yielding the highest gross margin, and is consequently the recommended combination for Bioclimatic Group 10. At the hot Mposa site, 'Chinese Cavendish' (54.21 ha(-1) an(-1) proved to be the most productive cultivar. The density of 2 500 plants ha(-1) outproduced (57.4 t ha(-1) an(-1) the lower densities and also generated the highest economic returns. However, when the cultivar/density interaction was evaluated, 'Chinese Cavendish' at the lower density of 2 105 plants ha(-1) realised the highest gross margin and is consequently the recommended combination for Bioclimatic Group 1.
Soil boron application for the alleviation of boron deficiency of avocado (Persea americana Mill.) in the KwaZulu-Natal Midlands.
(1997) Bard, Zac Jon.; Wolstenholme, B. Nigel.; Cowan, Ashton Keith.
The avocado tree's requirement for additional boron in B deficient soils has traditionally been met solely by foliar sprays in South Africa. Since boron is regarded as poorly phloem translocated in most plants including avocado, foliar applications are unlikely to cater for the requirement of the entire tree. Foliar sprays are made prior to leaf analysis so that artificially high readings are likely. A survey of the boron status of four KwaZulu-Natal avocado orchards showed all soils to be in the deficient range, viz. <1 mg kg(-1). Leaf analysis records on these estates appeared inflated with more than occasional spurious results. Despite marginally adequate leaf boron concentrations, widespread deficiency symptoms were noted in all orchards. For foliar application, leaf analysis of spring flush leaves does not provide a true indication of orchard boron status. Soil applications of borax (11 % B) in the range 0 to 60 g m(-2) (soil canopy area) year(-1) split into three applications, succeeded in increasing orchard B levels to above the recommended optimum of 40 mg kg(-1) without any deleterious effects visible on the feeder roots or tree, except at the highest rates. Initial uptake of soil B was slow, particularly in older orchards and with standard rates as developed in Australia (typically between 5 and 20 g m(-2) year(-1), split into at least 3 applications). Higher application rates (40 and 60 g m(-2) year(-1) showed greater effectiveness at raising leaf boron concentrations, particularly in the second season. Toxicity occurred with 40 and 60 g m(-2) year(-1) rates, 18 months after initial applications were made. High application rates indicated the tolerance of established avocado orchards to very high soil B concentrations. Soil applications increased fruit yield through increased fruit size in younger 'Hass' trees. Older, more deficient orchards did not show increased fruit size within the experimental timespan. Glasshouse trials supported findings in that soil B applications significantly increased leaf B concentrations (P < 0.001) proportional to soil application rate. Recently grafted young potted trees were extremely sensitive to soil boron applications which were not split, with toxicities occurring at low application rates. 'Edranol' seedling, a rootstock of Guatemalan origin was shown to be ca. 40 % more efficient in boron uptake than clonal 'Duke 7', the widely used rootstock in South Africa. Results indicate that boron deficiency is primarily the result of soil deficiency rather than poor rootstock uptake and translocation. On the Inanda soil type used and under the conditions of the experiments, it is suggested that application rates do not exceed 20 g borax m(-2) year(-1) (split into 3 applications) in severely deficient trees (10-30 mg kg(-1) B leaf analysis), and rates of ca. 10 g borax m(-2) year(-1) would be adequate in marginally deficient trees.
Abscisic acid metabolism in a Citrus Sinensis flavedo enzyme system.
(1998) Kalala, Maloji.; Cowan, Ashton Keith.
This research project had its major objective the unequivocal demonstration that the plant growth regulator, abscisic acid could be produced in vitro from labelled precursors. In addition, this project was intended to demonstrate the metabolic relationship between β, β-xanthophyll turnover and ABA biosynthesis. Finally attempts were made to isolate the enzyme responsible for the cleavage of the immediate xanthophyll precursor to ABA, 9'-cis-neoxanthin. This was achieved using a cell-free system developed from Citrus flavedo which demonstrated formation of xanthoxal and abscisic acid from zeaxanthin, antheraxanthin, violaxanthin and neoxanthin. In addition product abscisic acid was shown to incorporate label from mevalonic acid lactone establishing the terpenoid origin of this plant growth regulator. 9'-cis-neoxanthin cleavage enzyme was present in the Citrus cell-free system, partially purified, and separated from lipoxygenase activity and shown to convert 9'-cis-neoxanthin into xanthoxal and related but unidentified neutral products.
Vapour heat treatment of 'Hass' and 'Fuerte' avocado (Persea americana Mill.) fruit for extending storage life.
(1998) Weller, Philip Lawrence.; Wolstenholme, B. Nigel.
In an attempt to extend storage life of 'Hass' and 'Fuerte' avocado {Persea americana Mill.) fruit postharvest vapour heat treatments were used. Vapour heat treatment temperature regimes were 36, 38, 40 and 42°C for either 1, 2, 4 or 8 hours. After vapour heat treatment, fruit were cold stored at 3.5°C, for 5 or 6 weeks each. On removal from cold storage fruit were evaluated for firmness, and ripened at room temperature. Once ripe fruit were evaluated for heat/cold damage, days to ripening, weight loss and physiological disorders. These experiments were conducted during the 1996 and 1997 'Fuerte' and 'Hass' avocado seasons. Electron microscope analysis of vapour heat treated fruit revealed heat damage to the epidermis and fruit organelles of certain treatments. The effect of vapour heat treatment on protein synthesis on 'Fuerte' and 'Hass' avocado was investigated using gel electrophoresis, to determine if presumed heat shock proteins were synthesized under the treatment conditions. The activity of pectin methyl esterase was also investigated on the heat treated 'Fuerte' and 'Hass' avocados, to investigate if heat alters the activity of this enzyme. All experiments showed that vapour heat treatment extended 'Fuerte' and 'Hass' avocado storage and shelf life. Evaluation of the time/temperature combination for vapour heat treatment for each cultivar indicated that extension of shelf life was, in some cases, limited by rind heat damage. For the 1996 season, the best time/temperature combination for 'Fuerte' was at 38°C between 4 to 8 hours, 40°C between 4 to 8 hours and 42°C between 2 to 4 hours. For 'Hass', best results were achieved at 38°C between 4 to 8 hours. For the 1997 season, 'Fuerte's best time/temperature combination were at 36°C for 8 hours, 42°C between 1 to 2 hours and marginal results at 38°C between 4 to 8 hours. For 'Hass' the best time/temperature combination were achieved at 38°C and 40°C for 8 hours. Analysis of fruit flesh protein indicated changes associated with vapour heat treatment, and even induction of new proteins, perhaps heat shock proteins, giving 'Fuerte' and 'Hass' avocados beneficial characteristics such as an extension of shelf life. There was a decline in activity of pectin methyl esterase after vapour heat treatment, which was associated with a longer shelf life.
Biosynthetic origin of abscisic acid in ripening avocado fruit.
(2000) Guillaume Maurel, J. C.; Cowan, Ashton Keith.
Mesocarp of ripening avocado fruit incorporated label from [2-(14)C]mevalonolactone, [1-(14)C] acetic acid, [1-(14)C] glucose and [1 -(14)C] pyruvate into ABA, although incorporation from mevalonolactone was significantly higher. Inhibition of the mevalonate pathway at the HMGR level using mevastatin reduced incorporation from acetate and MVL, while increasing incorporation from pyruvate and glucose. The carotenoid biosynthesis inhibitors AMO 1618 (inhibitor of lycopene cyclase) and fluridone (inhibitor of phytoene desaturase) both decreased incorporation of MVL into ABA, while the plant growth regulators ancymidol (inhibitor of GA synthesis and cytochrome P450) and jasmonic acid (senescence stimulator reducing the carotenoid content of plants) both increased incorporation of MVL into ABA. Tungstate was found to reduce incorporation from all four substrates into ABA, although more significantly from MVL and acetate. Further investigation revealed that the tungstate induced decrease in MVL incorporation into ABA occurred concomitantly with increased label incorporation into XAN. Cobalt, an inhibitor of ACC oxidase and therefore of ethylene production, increased incorporation of MVL into ABA. Nickel had a similar effect. Analysis of the methyl ester of ABA extracted from avocado mesocarp supplied with either [1-(13)C] acetic acid or [1-(13)C] glucose revealed incorporation of label from acetate consistent with formation of ABA via the acetate/mevalonate pathway whereas glucose was incorporated via the triose phosphate pathway of isopentenyl pyrophosphate formation. Methane, positive ion-chemical ionisation-mass spectrometry of the cis, trans and all- trans isomers of ABA indicated more intense labelling of trans, trans-ABA, irrespective of substrate used. These results indicate that trans, trans- and cis, trans-ABA are derived by different pathways and that ABA is formed in avocado by both the mevalonate and non-mevalonate pathways of isopentenyl diphosphate synthesis.
In vitro culture of avocado : a model system for studying the biochemistry of fruit growth.
(2000) Mitchell, Dudley Ian.; Cowan, Ashton Keith.
The avocado (Persea americana Mill.) is considered by many to be a horticultural problem. Cultivars in use today have several drawbacks associated with yield, disease susceptibility and fruit quality. Breeding programs to counter these disadvantages have been met with limited success due mainly to the crop's heterozygosity, outbreeding nature and long juvenile period. Furthermore, genetic information regarding current commercial scions and rootstocks is limited and crosses are made based on parental phenotypic characteristics which are not always additive. It is proposed that the development of a protoplast-to-plant system for avocado would not only provide a means for plant breeders to overcome these problems, but would also present researchers with a useful tool for studying biochemical and physiological mechanisms operating within the plant. An investigation into the development of an in vitro system for use in metabolic studies was carried out. This technology was then used as a model system for studies into the metabolic control of cell growth. An attempt was made at developing a protoplast system from the mesocarp tissue of 'Hass' avocado. It was found that the purity and activity of the cellulase preparation in the protoplast isolation medium was critical. Failure to generate a protoplast system from mesocarp tissue prompted an investigation into the development of cell cultures. Mesocarp, seed and embryo tissue was subjected to various treatments in an attempt to induce callus for use as a source material for cell cultures. Callus derived from nucellar tissue of 'Hass' avocado seed at high concentrations of a-naphthalene acetic acid (NAA)(5 mgL-1 ) and isopentenyladenine (iP)(5 mgL-1 ) in Murashige and Skoog media (MS) proved to be the most amenable to subculture into liquid medium. Cell suspensions initiated from this callus grew fastest in MS media supplemented with NAA (5 mgL-1 ) and iP (1 mgL-1) These cell suspensions were maintained through subculture and were selected for use in metabolic studies. Cytokinin-dependent cell cultures from avocado seed callus were used to study the involvement of isoprenoid products in cell division. Addition of mevastatin, a competitive inhibitor of the key enzyme in the isoprenoid pathway, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), caused a reduction in cell growth at low concentrations (0.01 µM, 0.1 µM and 1 µM) and cessation of growth at higher concentrations (10 µM and 40 µM). Co-treatment with the isoprenoid compounds mevalonic acid lactone (MVL)(6 mM) and farnesyl diphosphate (FDP)(10 µM) completely reversed the effects of mevastatin at the 1 µM and 40 µM levels. The addition of stigmasterol (10 µM) to cell cultures treated with mevastatin (1 µM and 40 µM) resulted in a slight positive growth response indicating partial alleviation of inhibition. However, the response was not significantly different from the control suggesting that sterols played a minor role in cell division. It was concluded that isoprenoid-derived products played a critical role in the regulation of the cell cycle. Furthermore, it was suggested that mevastatin-induced HMGR inhibition gave rise to a response, most likely ABA-mediated, that acted antagonistically to regulatory mechanisms controlled, in part, by isoprenoid compounds.
The biochemical basis of colour as an aesthetic quality in Citrus sinensis.
(2001) Oberholster, Renate.; Cowan, Ashton Keith.
The development of fruit colour in the sweet orange (Citrus sinensis) is a cultivar characteristic affected by climate and environment. Although external colour is not always an indication of internal quality or maturity, it is probably the most important factor determining consumer acceptance. In the present investigation, efforts were made to determine the biochemical basis of colour as an aesthetic quality in C. sinensis 'Navel' and 'Valencia'. Furthermore, the changes in pigment content and composition during the period of colour development were recorded. Finally, in an attempt to manipulate citrus colour, the effect of dehydrating agents (alcohols), plant hormones, micro-nutrients and low temperature on flavedo carotenoid content was determined. Saponification of the two major colour-imparting components resolved by thin layer chromatography, followed by reversed-phase high performance liquid chromatography revealed that the principal colour-imparting pigments in C. sinensis flavedo are the yellow-coloured xanthophyll 9-Z-violaxanthin and the red C(30) apocarotenoid β-citraurin. Both pigments occur in the flavedo in esterified form. Identification of the chromophores was based on co-chromatography and online spectral analysis. The colour quality of mature fruit was dependant on the content and relative amounts of 9-Z-violaxanthin and Pcitraurin. Quantitative results revealed that increased colour intensity of citrus flavedo was associated with a decline in the 9-Z-violaxanthin : β-citraurin ratio from greater than 50 to below 10, and an increase in 9-Z-violaxanthin and β-citraurin content. Measurement of the mass and ratio of these pigments can be used to accurately colour-grade orange fruit for local and export markets. These parameters will also aid in the evaluation of colour manipulatory techniques. Visual colour break in C. sinensis appears to be associated with a minimum in total pigment as well as total carotenoid content. The period prior to colour break is characterised by a reduction in chlorophylls, carotenes and free xanthophylls usually associated with photosynthetic activity. Following colour break, a massive increase in xanthophyll acyl esters (particularly 9-Z-violaxanthin) is observed. Efforts were made to manipulate carotenoid content of citrus flavedo in vivo, with a view to manipulate fruit colour commercially. It was shown that the micro-nutrients tungsten and molybdenum, and the plant hormones abscisic acid and jasmonic acid increased carotenoid content of flavedo discs; whereas the plant hormone gibberellic acid decreased carotenoid levels. The dehydrating agents ethanol and butanol increased carotenoid content in whole fruit flavedo and flavedo discs. Optimum concentrations were shown to be 20-30% (v/v) for ethanol and 5-10% (v/v) for butanol.
Optimisation of propagation methods in Prunus persica (L.) Batsch.
(2001) Lebese, Thabiso C.; Bertling, Isa.; Bower, John Patrick.
Propagating methods for peach (Prumis persica L. Batsch.) are currently limited to the use of seeds or cuttings. Most of the rootstocks commonly used for establishing peach trees commercially originate from a narrow genetic base. The most commonly used peach rootstock in South Africa is 'Kakamas', which has disadvantages such as slow growth, and a high susceptibility to certain pests and diseases. 'Kakamas' is classified as a mid to late ripening cultivar, hence, its use as a rootstock is restricted in early ripening cultivars. Optimising peach seedling and cutting production may on the other hand increase more selection material that will increase genetic variability and also serve as the basis for future production and selection of rootstocks for peach nursery establishments. Hence, this study was designed to improves success of peach cutting production by increasing the rooting percentage and the survival rate of cuttings. This was firstly achieved by the application of various concentrations of IBA and several rooting-cofactors. Secondly, rooting success of cuttings taken at different seasons was studied. The response of two cutting positions to various IBA and rooting-cofactor was evaluated. Attempts were also made to overcome the requirement of peaches for a seed stratification period by using plant growth regulators. Studies to optimise the establishment and growth of embryos of early to late ripening cultivars ('Klara', 'Oom Sarel' and' Summer Giant') in vitro were undertaken to overcome the problem of small underdeveloped embryos which are often obtained from early ripening peach cultivars. The early ripening peach cultivars 'DeWet', 'Earlibelle' and 'Florida Prince' were propagated by softwood, semi-hardwood and hardwood cuttings prepared from August 1999 to July 2000. It was found that softwood cuttings prepared in October and November responded well to an IBA application of 1000 mg 1(-1), resulting in 100 % rooting in all three cultivars. In 'Florida Prince' and 'DeWet' the rooting-cofactors chlorogenic acid and phloroglucinol at the concentration of 100ug 1(-1) yielded 77 % and 81 % rooting, respectively while quercitin and rutinin gave only 46 and 44 % rooting for all cultivars. The basal portion of the cutting rooted better than the terminal portion (78 % versus 58 %). Rooting percentage differed in all treatments in response to IBA application and rooting-cofactors 74 % for 'Florida Prince', 62 % for 'DeWet' and 54 % for 'Earlibelle'. The use of IBA and Ca-EDTA proved to be beneficial for rooting of 'Florida Prince' cuttings and resulted in a rooting percentage of 86 % in wounded hardwood cuttings of this cultivar. It was also shown that the simple sugars glucose, fructose and sucrose as well as the sugar alcohols sorbitol and mannitol accumulated at the base of the cutting during adventitious base root formation if the cutting bases were treated with 1000 mg 1(-1) IBA. The concentration of these sugars and sugar alcohols were lower in untreated cuttings compared to IBA treated cuttings during the adventitious root formation process. Studies on the origin of adventitious root formation in stem cuttings of peaches were conducted using light microscopy and transmission electron microscopy. These studies revealed that adventitious roots originate (in peaches) in the vicinity of the vascular bundle tissue and in the cells around them. It was found, however, that adventitious root formation in IBA treated cuttings is associated with the formation of root primordia. These may trigger root initiation and ultimately the development of adventitious roots. In embryo culture studies the highest number of roots and greatest length of roots per embryo as well as the highest number of embryos forming roots was achieved when either the medium of Murashige and Skoog (MS) (1962) or of Steward and Hsu (SH) (1978) were employed. The Woody Plant medium (Lloyd and McCowan, 1978) and the medium after Schenk and Hildebrandt (1972) were found to be less effective when compared to MS and SH media. Addition of GA(3) (0.01 mg 1(-1)), BAP (0.2 mg 1(-1)) or GA(3) (0.01 mg 1(-1))+ BAP (0.2 mg 1(-1))+IBA (0.5 mg 1(-1)) to the media gave the best results with respect to embryos forming roots (86 %), number of roots per embryo (8.0) and total length of roots per embryo (7.57 cm). Furthermore, the following conditions for optimal rooting of peach embryos were established: pH 5.2, 1.5 g 1(-1) agar, 60 g 1(-1) sucrose and 16h light/8h darkness photo period. Further studies on the influence of the stratification temperature on germination of embryos revealed the highest germination percentage after exposure to 40 C ±2 constantly for 30 to 60 days. However, this chilling requirement can be successfully substituted by the addition of GA(3) , kinetin, zeatin, BA and thiourea to the culture media.
Effects of potassium and mulching on Persea americana Mill. cv. Hass pheno/physiology, yield and fruit size.
(2001) Van Niekerk, Warren; Bower, John Patrick.; Johnston, M. A.
No abstract available.
Means of improving colour expression in pepper fruit.
(2003) Mosoeunyane, Molipa.; Bertling, Isa.; Bower, John Patrick.
Colour is a characteristic that makes fruit appealing to the consumer, hence, is a prime factor when (s)he chooses to buy certain horticultural commodities. If colour is unappealing, consumers tend to ignore other quality characteristics of the fruit. Although colour expression in Capsicum annuum L. is genetically influenced, it is also affected by environmental factors as well as crop management practices. In an attempt to identify which are the dominant red colour-imparting carotenoids in red pepper and how to influence their occurrence, extracts from crude and saponified mature-green, colour-break and red-ripe fruit were purified on TLC silica gel 60 GF(254) plates. TLC R(f) values of the identified intensive red bands from saponified red-ripe extract were compared to those of authentic capsorubin, capsanthin, 13-Z-capsanthin and 9-Z-capsanthin standards. Two dominant red carotenoids were isolated from red-ripe fruit, by separating either crude or saponified extract by TLC. The two bands were then subjected to reversed-phase HPLC analysis. Both bands were characterized by comparison of their absorption spectra to that of authentic capsanthin and capsorubin standards. Red colour imparting compounds of the red pepper cultivar Capistrano surfaced at colour-break stage and their intensity increased with the ripening process. HPLC results show that there was structural modification of ketocarotenoid, mainly capsorubin. Trials were carried out in a plastic tunnel and in a growth room to investigate the impact of various plant management practices (moisture regimes, macronutrient applications, thinning of reproductive structures, subjecting pepper plants to optimal growing temperature) on pepper fruit pigment concentration. This concentration was determined at the mature-green and red-ripe stage. Subjecting pepper plants to optimal growing temperature (23/18°C) from the vegetative stage onwards, providing them with recommended optimal amount of K fertilizer (25.2 Kg ha-1 ) and supplying Mg at supra-optimal level (455 Kg ha-1 ) as well as subjecting them to drought stress starting from 30 or 50 days after transplanting and water logging conditions from 30 days after first petal fall onwards increased pepper fruit carotenoid concentration significantly. On the other hand, other levels of the above-mentioned factors (subjecting pepper plants to the optimum temperature later than the vegetative stage, supplying 'very low', 'low' or 'high' K or, 'very low', 'low' or 'medium' Mg concentrations as well as thinning of reproductive structures of pepper plants early in the fruit developmental stage and subjecting plants to drought from 30 days after first petal fall onwards or to water-logging from 50 days after transplanting or 30 days after first petal fall onwards) resulted in a significant decrease in the carotenoid concentration. Therefore, management practices can be explored to improve red colour formation in red-ripe Capsicum fruit.
Floral induction in Eucalyptus nitens (Deane and Maiden) Maiden in South Africa.
(2003) Gardner, Robin Arthur William.; Bertling, Isa.
Eucalyptus nitens (Deane & Maiden) Maiden is an important, commercial eucalypt planted predominantly for pulpwood in several southern hemisphere countries. In South Africa, the erratic and sparse flowering habit of E. nitens severely impedes genetic improvement and commercial seed production in the species. The comparatively abundant flower bud production at specific high altitude sites in the summer rainfall region suggested that cumulative cold may be implicated in the floral induction process. Series of field trials and semi-controlled environment trials were undertaken between 1996 and 2001 to investigate this. Three chill models were used to investigate whether winter temperature data can be related to E. nitens flower bud production. In the field trials, not only was the relationship between winter chilling and subsequent flower bud crop investigated, but also the relationship between cumulative winter drought conditions and floral bud production. In the trials under semi-controlled environmental conditions, the effect of applied winter chilling on floral bud production and photosynthetic efficiency was investigated. In the field trials, amount of accumulated winter chill, in conjunction with paclobutrazol treatment, was able to explain between 66 and 72 % of the variation in E. nitens flower bud production at four and five years after planting. Very high levels of accumulated winter chill (≥ 88 Chilling Portions (CPs) of the Dynamic Model) stimulated a high percentage of seedlings (25 - 50 %) and grafts (55 -77 %) to produce flower buds. At low to moderate levels of winter chill (41 to 72 CPs), paclobutrazol application increased flower bud production significantly, but at high levels of winter chill (> 76 CPs) paclobutrazol had a negligible effect. Cumulative winter drought did not promote floral bud production. In the semi-controlled environment trials, cold suppressed vegetative growth and induced flowering in pac!obutrazol-treated 18-month old grafted trees. Cold without paclobutrazol did not promote floral bud production. The results suggest that accumulated winter chill units (according to the Dynamic Model) are more effective than accumulated cold hours (hours below 5 degrees C). A high number of cold hours (1366 hours) reduced photosynthetic efficiency, but did not induce flowering. Furthermore, photosynthetic efficiency remained high for the moderate cold treatments which did induce flowering, suggesting that stress is not correlated to flowering in E. nitens. The results of the field and semi-controlled environment trial series suggest that precocity and floral productivity in E. nitens are under strong genetic control. Better accuracy in predicting flower bud crops in E. nitens could probably be achieved by excluding genetic variability and increasing the range of chilling conditions in such trials in future. The results indicate that future research should focus on the identification of optimum chilling (temperature) criteria for floral induction in E. nitens, the use evaporative cooling in seed orchards to reduce warm winter daytime conditions, the possible use of low-chill rootstocks, and the location of orchards as far south as possible in the winter rainfall region to achieve maximal exposure to temperatures which fulfil the chilling requirement of the species.
Postharvest maintenance of the shelf life and quality attributes of banana and papaya.
(2003) Ghebreslassie, Biniam M.; Bower, John Patrick.; Bertling, Isa.
Banana and papaya are two commonly grown fruits of the tropical regions of the world. Like most tropical climacteric fruits, these fruits have a short shelf life and deteriorate rapidly after harvest. This becomes more pronounced in tropical areas where cold chain management practices are poor and the ability environmental control is limited. To extend the shelf life with maintained quality of the fruits and to investigate the effect of various postharvest treatments a study was conducted on banana cv. Williams and on papaya cv. Hortus Gold. The treatments included storage in different packaging materials such as micro perforated polypropylene bags (MPB), Micro perforated polypropylene bags with ethylene absorbent (MPB+K), macro perforated polypropylene bags coated with anti mist coating (PP), fruit waxing, gibberellic acid (GA3) and indole butyric acid (IBA) applications. Comparison was made against untreated fruits. Banana fruits were held at 12, 15 and 22°C, while papaya fruit were held at 5.5, 7, 10 and 22°C. Percentage weight loss (PWL), firmness change, visual colour development and respiration rate were evaluated on a weekly basis during the storage period. Selected quality attributes such as total soluble solids (TSS), pH, total chlorophyll, total carotenoids and organic acids for banana and TSS, pH, titratable acid (TA) and sugar:acid ratio for papaya were analyzed at the end of the storage period. PWL, softening, colour development and respiration rate increased significantly (P
Aspects of improving cold hardiness of tomato (Lycopersicon esculentum) var. Rossol.
(2004) Ghebretinsae, Amanuel Ghebrehiwet.; Bertling, Isa.; Bower, John Patrick.
Tomatoes, particularly those of the determinate type, are one of the most popular vegetables in the East African country Eritrea. The crop is a source of income to small farm operators as well as commercial growers, and plays an important role in the nutritional supply of the population. Nonetheless, tomato production is limited during the cool season resulting - on the one hand - in a reduced nutritional supply during this period and - on the other hand - in an increased economic potential of the crop. Although performance of tomato plants under low temperature conditions is genetically influenced, prevailing temperatures as well as management practices also affect growth and development. In order to understand the long-term effects of a cold spell on tomato plants, experiments were carried out to determine the effect of a cold spell on plant vegetative and reproductive characteristics of determinate type ''Rossol'' tomatoes. Plants were moved for two to five subsequent nights from a tunnel to a cold room (4°C). The fruit set stage of "Rossol" tomatoes was found to be most sensitive to cold temperature, followed by the flowering stage. The juvenile stage was, of all the developmental stages examined, the least sensitive to cold. Furthermore, subjecting tomato plants for five subsequent nights (cumulative 60hrs) to 4°C resulted in a significant retardation of growth and development and in yield reduction. However, tomatoes exposed to a two-night cold spell during either the vegetative or the flowering stage recovered quickly and, ultimately, performed well. Furthermore, trials were carried out under tunnel and field conditions to investigate the impact of potassium application as well as mulching on cold tolerance of "Rossol" tomatoes. Under low temperature conditions, increasing the level of potassium to up to 150% of the recommended level (157.5kg*ha-1 ) resulted in quicker ontogenetic development and increased yields significantly. On the other hand, supplying tomato plants with 50% and 200% of the recommended potassium level reduced growth, delayed development and decreased yield and yield attributes. Using black plastic mulch also increased plant growth and speeded up plant development. Maize stover mulch, however, retarded plant growth and development so that certain stages ofthe phenological cycle were reached later than by non-mulched plants. However, yield and yield attributes increased significantly using stover mulch. Therefore, the management practises potassium fertilization and mulching provide excellent tools to increase the tolerance of tomato plants to low temperature conditions. Furthermore, organic mulches can be used to delay crop development and time maturity to achieve high retail process of the commodity in the cool winter months.
Development of a sulphur free litchi storage protocol using sealed polypropylene bags.
(2006) Archibald, Alison Joy.; Bower, John Patrick.; Bertling, Isa.
The use of sulphur as a method of postharvest disease control and colour retention in litchis is soon to be restricted by the European Union. It is therefore essential that new postharvest treatments and packaging techniques be developed in order to retain internal and external fruit qualities and thus allow for export. Good litchi quality is not only important for the export market but also for use on the local market. In this study, alternative methods for postharvest quality control were investigated with the aim of extending the litchi storage life to 40 days under modified storage. Packaging the fruit in polypropylene bags significantly decreased fruit water loss and resulted in an increase in shelf life, as determined by red colour and overall rind appearance. There was no distinct advantage of amodified atmosphere. The use of a punnet, lined with absorbent sheeting and placed within the sealed polypropylene bag, further improved the shelf life. The absorbent sheeting reduced the amount of free water and resulted in little pathogen infection, while the punnet was effective in protecting the fruit from damage. It was notable that most water loss occurred within the first 10 days of storage and that the majority would actually take place during the cooling phase. A hydrocooling technique was therefore investigated and was found to not significantly decrease water loss, possibly due to not hydrocooling the fruit for a long enough period of time. Temperature management was extremely important for both colour retention and pathogen control. It was found that treatments stored at 5.5QC showed better colour retention after the 40 days storage than the 1QC storage treatment. The higher storage temperature, however, enhances the potential for postharvest diseases. Three compounds, namely ISR 2000, 'Biosave' and F10, were tested for pathogen control. 'Biosave' showed the best results with the most effective concentration being 100 mill water and good pathogen control occurred when storage was at 10 C. Polyphenol oxidase (PPO) activity in the litchi rind was evaluated as it is thought to be closely related to browning of litchi fruit, probably due to the degradation of phenolics by PPO. Brown fruit had a high PPO activity whilst red fruit had much lower activity. It was also shown that PPO activity decrease over storage time, possibly due to product inhibition of the enzyme. The internal quality of the fruit was determined using the T88: acid ratio of the pulp, as it is well correlated to mean eating quality. For fruit to have excellent taste, it must have a T88: acid ratio of between 31:1 and 60:1. All the fruit had a ratio that met this criterion and would therefore ensure good eating quality.
Investigation into the feasibility of a dairy processing enterprise through action research with a group of women from an LRAD project.
(2007) Mans, Susanna Elizabeth.; Hendriks, Sheryl Lee.
Poverty is caused by inadequate income. Effective assistance to small-scale enterprises may benefit the urban and rural poor. Small enterprises have the potential to create employment, reduce poverty and support sustainable livelihoods, as small enterprises satisfy local needs, provide employment opportunities in local areas, increase income, ensure food security and improve health. The Department of Land Affairs has recently introduced policies such the Land Reform Policy to correct the injustices of South Africa’s past. During 2005, the KwaZulu-Natal Department of Agriculture and Environmental Affairs introduced the Agrarian Revolution Programme, in an effort to close the gap between the first and second economy. The Agrarian Revolution and the LRAD programmes encourage agribusinesses through the formation of co-operatives or trusts. The purpose of this study was to investigate the potential of an envisaged processing enterprise with a group of women from an LRAD project, within the Engadini Community Trust. An action research methodology was followed. A training manual was developed and training conducted with the Engadini women’s group through which they prepared a business plan, developed prototype products; conducted market research; estimated prices for the products and developed a marketing plan. The study results indicate that the group would have the technical skills to make a good quality product. The group is likely to face problems ensuring a sustainable supply of raw materials as the current supply of milk would hardly be sufficient to supply the target market sampled during the consumer survey. The success of the dairy processing enterprises depends heavily on the ability of the Engadini Trust to overcome internal social problems. Conflict between the Engadini dairy processing enterprise members and conflict within the larger Engadini Community Trust had a crippling effect on the dairy processing enterprise. The main recommendations for the group are that the group needs to secure a sustainable supply or fresh milk. A dairy processing facility that will meet food safety standards needs to be erected for the enterprise. The location of the dairy processing enterprise needs to be re-considered. To overcome internal conflict within the group, the women’s group needs to gain representation on the Engadini Community Trust’s Executive Committee, to ensure that the dairy processing enterprise interests are considered by the Trust. The main recommendations for small-scale enterprises are that they should ensure to have sustainable supply of good-quality raw materials and a reliable, sustainable market, even if the market is relatively small. Policy recommendations are that Government Departments such as the KwaZulu-Natal Departments of Agriculture and Environmental Affairs and Economic Development should consider adapting policies that will focus on funding individual enterprises, rather than group enterprises. A directorate or sub-directorate dedicated to the development of small and medium sized food processing enterprises should be created. The marketing section of the KwaZulu- Natal Department of Agriculture and Environmental Affairs should provide marketing information for small-scale food processing enterprises available to extension officers and small-scale enterprises.

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