Investigating the role of mycorrhizal fungi and associated bacteria in promoting growth of citrus seedlings
- Authors: Sitole, Phumeza
- Date: 2014
- Subjects: Mycorrhizal fungi , Citrus -- South Africa , Citrus -- Diseases and pests -- Biological control -- South Africa , Fungi as biological pest control agents , Bacteria , Phytophthora , Pythium , Indoleacetic acid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4111 , http://hdl.handle.net/10962/d1013033
- Description: South Africa is the world's second largest exporter of fresh citrus and is ranked 14th in citrus production. Fungal pathogens such as Phytophthora and Pythium cause economic losses as a result of root rot and brown rot. Mycorrhizal fungi are specialized members of the fungal community forming a mutualistic relationship with plant roots. Mycorrhizal fungal structures are known to associate with other soil microorganisms and these may contribute to improved plant growth. A diverse group of bacteria that interact with the mycorrhizal fungi are known as Mycorrhizal Helper Bacteria (MHB). The aim of this study was to investigate the role of arbuscular mycorrhiza and associated bacteria isolated from spores and determine whether they had any plant growth promoting potential. A total of 19 bacteria were isolated from arbuscular mycorrhizal spores and were molecularly identified as belonging to several Bacillus, Micrococcus, Onchrobactrum and Staphylococcus sp. All bacterial isolates were tested for plant growth promotion abilities. One Bacillus isolate was able to solubilise phosphate. Four isolates Micrococcus sp, Micrococcus leteus, Ochrobacterum sp and Ochrobacterum antropi were able to produce Indole Acetic Acid and three isolates showed potential to reduce growth of Phytophthora nicotianae, P. citrocola and P. citrophthora in in vitro plate cultures. Further tests using culture supernatants of the Bacillus sp, Micrococcus sp and Bacillus cereus confirmed their ability to inhibit or reduce growth of the three Phytophthora species in a 96 well bioassay. Bacillus sp and Bacillus cereus were able to inhibit Phytophthora spp by 95 to 100 % and Micrococcus spp was able to decrease pathogen growth by 60 to 94 %. These bacterial isolates were further evaluated for plant growth promoting abilities on citrus rough lemon seedlings alone or in combination with arbuscular mycorrhizal inoculum. Bacterial and mycorrhizal inoculants influence the increase in shoot and root biomass. Bacillus cereus in combination with mycorrhizal inoculum significantly increased seedling shoot to root ratio while root biomass was significantly increased with mycorrhizal inoculation. Due to the short duration of the trial mycorrhizal colonisation could not be assessed. It is evident that selected combinations of bacteria and mycorrhizal fungi could promote citrus seedling growth and potentially improve seedling health. Further studies under nursery conditions are recommended.
- Full Text:
- Date Issued: 2014
- Authors: Sitole, Phumeza
- Date: 2014
- Subjects: Mycorrhizal fungi , Citrus -- South Africa , Citrus -- Diseases and pests -- Biological control -- South Africa , Fungi as biological pest control agents , Bacteria , Phytophthora , Pythium , Indoleacetic acid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4111 , http://hdl.handle.net/10962/d1013033
- Description: South Africa is the world's second largest exporter of fresh citrus and is ranked 14th in citrus production. Fungal pathogens such as Phytophthora and Pythium cause economic losses as a result of root rot and brown rot. Mycorrhizal fungi are specialized members of the fungal community forming a mutualistic relationship with plant roots. Mycorrhizal fungal structures are known to associate with other soil microorganisms and these may contribute to improved plant growth. A diverse group of bacteria that interact with the mycorrhizal fungi are known as Mycorrhizal Helper Bacteria (MHB). The aim of this study was to investigate the role of arbuscular mycorrhiza and associated bacteria isolated from spores and determine whether they had any plant growth promoting potential. A total of 19 bacteria were isolated from arbuscular mycorrhizal spores and were molecularly identified as belonging to several Bacillus, Micrococcus, Onchrobactrum and Staphylococcus sp. All bacterial isolates were tested for plant growth promotion abilities. One Bacillus isolate was able to solubilise phosphate. Four isolates Micrococcus sp, Micrococcus leteus, Ochrobacterum sp and Ochrobacterum antropi were able to produce Indole Acetic Acid and three isolates showed potential to reduce growth of Phytophthora nicotianae, P. citrocola and P. citrophthora in in vitro plate cultures. Further tests using culture supernatants of the Bacillus sp, Micrococcus sp and Bacillus cereus confirmed their ability to inhibit or reduce growth of the three Phytophthora species in a 96 well bioassay. Bacillus sp and Bacillus cereus were able to inhibit Phytophthora spp by 95 to 100 % and Micrococcus spp was able to decrease pathogen growth by 60 to 94 %. These bacterial isolates were further evaluated for plant growth promoting abilities on citrus rough lemon seedlings alone or in combination with arbuscular mycorrhizal inoculum. Bacterial and mycorrhizal inoculants influence the increase in shoot and root biomass. Bacillus cereus in combination with mycorrhizal inoculum significantly increased seedling shoot to root ratio while root biomass was significantly increased with mycorrhizal inoculation. Due to the short duration of the trial mycorrhizal colonisation could not be assessed. It is evident that selected combinations of bacteria and mycorrhizal fungi could promote citrus seedling growth and potentially improve seedling health. Further studies under nursery conditions are recommended.
- Full Text:
- Date Issued: 2014
Thermoluminescence characteristics of synthetic quartz
- Authors: Niyonzima, Pontien
- Date: 2014
- Subjects: Thermoluminescence , Quartz , Emission spectroscopy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5538 , http://hdl.handle.net/10962/d1013190
- Description: Quartz is one of the most abundant natural minerals in the crust of the earth. Due to its dosimetric luminescence properties, it is employed in retrospective dosimetry, archaeological and geological dating. The intensity and the structure of the TL glow curves of quartz are strongly dependent upon the origin, impurity content, formation condition and pre-irradiation heat treatment. The aim of this project is to study the mechanisms of thermoluminescence (TL), Phototranssferred thermoluminescence (PTTL) and radioluminescence (RL) in synthetic quartz and to discuss the results in terms of physical characteristics of point defects involved. Thermoluminescence measurements were made on a sample of synthetic quartz in its as-received state (unannealed) synthetic quartz annealed at 500˚C for 10 minutes. The unannealed sample shows six TL glow peaks located at 94, 116, 176, 212, 280 and 348˚C at a heating rate of 5˚Cs⁻¹. The annealed sample shows seven TL peaks at 115, 148, 214, 246, 300, 348 and 412˚C at a heating rate of 5˚Cs⁻¹. The intensity of peak I, at 94 and 115˚C for the unannealed and annealed samples respectively, increases with irradiation. Peak I has an activation energy of approximately 0.90 eV and a frequency factor of the order of 10¹¹ s⁻¹. The order of kinetics is between 0.9 and 1.2. The unannealed synthetic quartz shows phototransferred thermoluminescence (PTTL) at the position of peak I after removal of the first three peaks followed by illumination. The PTTL intensities show peak shaped behaviour when plotted against illumination time. The PTTL showed a quadratic increase with dose. The material exhibits fading of PTTL intensity with delay time. Radioluminescence was measured on synthetic quartz unannealed and annealed annealed at 500, 600, 700, 800, 900 and 1000˚C for 10 to 60 min. The emission spectra of synthetic quartz show seven emission bands. The effect of irradiation on the RL spectra is to increase the intensity of all emission bands for samples annealed at temperatures less than or equal to 700˚C. The effect of annealing time is to increase the RL amplitude for the samples annealed at temperatures greater than 700˚C. The annealing temperature increases the RL amplitude of all emission bands of the spectrum for all samples.
- Full Text:
- Date Issued: 2014
- Authors: Niyonzima, Pontien
- Date: 2014
- Subjects: Thermoluminescence , Quartz , Emission spectroscopy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5538 , http://hdl.handle.net/10962/d1013190
- Description: Quartz is one of the most abundant natural minerals in the crust of the earth. Due to its dosimetric luminescence properties, it is employed in retrospective dosimetry, archaeological and geological dating. The intensity and the structure of the TL glow curves of quartz are strongly dependent upon the origin, impurity content, formation condition and pre-irradiation heat treatment. The aim of this project is to study the mechanisms of thermoluminescence (TL), Phototranssferred thermoluminescence (PTTL) and radioluminescence (RL) in synthetic quartz and to discuss the results in terms of physical characteristics of point defects involved. Thermoluminescence measurements were made on a sample of synthetic quartz in its as-received state (unannealed) synthetic quartz annealed at 500˚C for 10 minutes. The unannealed sample shows six TL glow peaks located at 94, 116, 176, 212, 280 and 348˚C at a heating rate of 5˚Cs⁻¹. The annealed sample shows seven TL peaks at 115, 148, 214, 246, 300, 348 and 412˚C at a heating rate of 5˚Cs⁻¹. The intensity of peak I, at 94 and 115˚C for the unannealed and annealed samples respectively, increases with irradiation. Peak I has an activation energy of approximately 0.90 eV and a frequency factor of the order of 10¹¹ s⁻¹. The order of kinetics is between 0.9 and 1.2. The unannealed synthetic quartz shows phototransferred thermoluminescence (PTTL) at the position of peak I after removal of the first three peaks followed by illumination. The PTTL intensities show peak shaped behaviour when plotted against illumination time. The PTTL showed a quadratic increase with dose. The material exhibits fading of PTTL intensity with delay time. Radioluminescence was measured on synthetic quartz unannealed and annealed annealed at 500, 600, 700, 800, 900 and 1000˚C for 10 to 60 min. The emission spectra of synthetic quartz show seven emission bands. The effect of irradiation on the RL spectra is to increase the intensity of all emission bands for samples annealed at temperatures less than or equal to 700˚C. The effect of annealing time is to increase the RL amplitude for the samples annealed at temperatures greater than 700˚C. The annealing temperature increases the RL amplitude of all emission bands of the spectrum for all samples.
- Full Text:
- Date Issued: 2014
A review of archean orogenic gold deposits in greenstone belts and the Slave Province : exploration in the Yellowknife domain, NWT, Canada
- Authors: Branson, Thomas Keegan
- Date: 2014
- Subjects: Gold ores -- Northwest Territories -- Yellowknife , Gold ores -- Geology , Gold mines and mining -- Northwest Territories -- Yellowknife , Greenstone belts -- Northwest Territories -- Yellowknife , Orogenic belts -- Northwest Territories -- Yellowknife , Prospecting -- Northwest Territories -- Yellowknife , Mining geology , Slave Province (N.W.T. and Nunavut)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5055 , http://hdl.handle.net/10962/d1012142 , Gold ores -- Northwest Territories -- Yellowknife , Gold ores -- Geology , Gold mines and mining -- Northwest Territories -- Yellowknife , Greenstone belts -- Northwest Territories -- Yellowknife , Orogenic belts -- Northwest Territories -- Yellowknife , Prospecting -- Northwest Territories -- Yellowknife , Mining geology , Slave Province (N.W.T. and Nunavut)
- Description: A review of Archean granite-greenstone terranes, orogenic gold deposits, the Slave Province and modern exploration tools, techniques and methods was conducted to identify prospective areas in the Yellowknife domain for hosting orogenic gold deposits and illustrate the best exploration methods for delineating this deposit type. This study identifies Archean granite-greenstone terranes as economically important hosts to quartz-carbonate vein-hosted orogenic gold deposits. These deposits occur at convergent plate margins, but can also be related to local extensional tectonics within a convergent setting. Heat generated from tectonic processes can trigger hydrothermal fluid movement along first-order faults and shear zones. Precipitation of gold-bearing quartz-carbonate veins from the hydrothermal fluids occurs in second- and third-order faults and shear zones related to the first-order structures. This study also identifies the Archean Slave Province in northern Canada as a well-endowed craton with numerous orogenic gold deposits, diamondiferous kimberlites, VMS deposits and several other mineralization styles. In particular, three greenstone belts (Yellowknife, Cameron River and Beaulieu River) associated with likely first-order structures are comprised of prospective rocks for hosting orogenic gold and VMS mineralization. The Yellowknife greenstone belt hosts the past-producing and former world-class Con and Giant orogenic gold deposits, but has been little explored with modern exploration techniques. The Cameron River and Beaulieu River greenstone belts host numerous base and precious metal VMS and BIF-hosted orogenic gold prospects and deposits, indicating mineralization is present. There is considerable potential for significant discoveries to be made using modern exploration techniques in the greenstone belts; however, exploration in the region has been hindered over the past decade by ongoing political negotiations. Once the political negotiations are finalized, application of modern exploration methods and techniques in the prospective greenstone belts should be carried out. Regional scale methodologies should be applied to generate targets using predictive modelling, implicit 3D modelling, 3D geochemistry and exploration targeting so decisions defining a businesses strategy for ground acquisition of high priority targets are made using quantitative analysis. Once ground is acquired, field-based exploration for orogenic gold and VMS deposits should include geological mapping with a focus on structural geology, geochemical sampling and airborne magnetic, radiometric and EM geophysical surveys. Prior to reconnaissance drilling, integration of all data layers and interpretation within a common 3D earth model should be conducted. Following successful reconnaissance drilling, definition drilling along strike and down dip of intersected mineralization, combined with borehole geophysics, should be carried out to delineate the extent of mineralization.
- Full Text:
- Date Issued: 2014
- Authors: Branson, Thomas Keegan
- Date: 2014
- Subjects: Gold ores -- Northwest Territories -- Yellowknife , Gold ores -- Geology , Gold mines and mining -- Northwest Territories -- Yellowknife , Greenstone belts -- Northwest Territories -- Yellowknife , Orogenic belts -- Northwest Territories -- Yellowknife , Prospecting -- Northwest Territories -- Yellowknife , Mining geology , Slave Province (N.W.T. and Nunavut)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5055 , http://hdl.handle.net/10962/d1012142 , Gold ores -- Northwest Territories -- Yellowknife , Gold ores -- Geology , Gold mines and mining -- Northwest Territories -- Yellowknife , Greenstone belts -- Northwest Territories -- Yellowknife , Orogenic belts -- Northwest Territories -- Yellowknife , Prospecting -- Northwest Territories -- Yellowknife , Mining geology , Slave Province (N.W.T. and Nunavut)
- Description: A review of Archean granite-greenstone terranes, orogenic gold deposits, the Slave Province and modern exploration tools, techniques and methods was conducted to identify prospective areas in the Yellowknife domain for hosting orogenic gold deposits and illustrate the best exploration methods for delineating this deposit type. This study identifies Archean granite-greenstone terranes as economically important hosts to quartz-carbonate vein-hosted orogenic gold deposits. These deposits occur at convergent plate margins, but can also be related to local extensional tectonics within a convergent setting. Heat generated from tectonic processes can trigger hydrothermal fluid movement along first-order faults and shear zones. Precipitation of gold-bearing quartz-carbonate veins from the hydrothermal fluids occurs in second- and third-order faults and shear zones related to the first-order structures. This study also identifies the Archean Slave Province in northern Canada as a well-endowed craton with numerous orogenic gold deposits, diamondiferous kimberlites, VMS deposits and several other mineralization styles. In particular, three greenstone belts (Yellowknife, Cameron River and Beaulieu River) associated with likely first-order structures are comprised of prospective rocks for hosting orogenic gold and VMS mineralization. The Yellowknife greenstone belt hosts the past-producing and former world-class Con and Giant orogenic gold deposits, but has been little explored with modern exploration techniques. The Cameron River and Beaulieu River greenstone belts host numerous base and precious metal VMS and BIF-hosted orogenic gold prospects and deposits, indicating mineralization is present. There is considerable potential for significant discoveries to be made using modern exploration techniques in the greenstone belts; however, exploration in the region has been hindered over the past decade by ongoing political negotiations. Once the political negotiations are finalized, application of modern exploration methods and techniques in the prospective greenstone belts should be carried out. Regional scale methodologies should be applied to generate targets using predictive modelling, implicit 3D modelling, 3D geochemistry and exploration targeting so decisions defining a businesses strategy for ground acquisition of high priority targets are made using quantitative analysis. Once ground is acquired, field-based exploration for orogenic gold and VMS deposits should include geological mapping with a focus on structural geology, geochemical sampling and airborne magnetic, radiometric and EM geophysical surveys. Prior to reconnaissance drilling, integration of all data layers and interpretation within a common 3D earth model should be conducted. Following successful reconnaissance drilling, definition drilling along strike and down dip of intersected mineralization, combined with borehole geophysics, should be carried out to delineate the extent of mineralization.
- Full Text:
- Date Issued: 2014
Changes and continuities in the labour process on commercial farms in post-Apartheid South Africa : studies from Eastern Cape and KwaZulu-Natal Provinces
- Authors: Kheswa, Nomzamo Sybil
- Date: 2014
- Subjects: Agricultural laborers -- South Africa -- Eastern Cape , Agricultural laborers -- South Africa -- KwaZulu-Natal , Agricultural wages -- South Africa -- Eastern Cape , Agricultural wages -- South Africa -- KwaZulu-Natal , Eastern Cape (South Africa) -- Rural conditions , KwaZulu-Natal (South Africa) -- Rural conditions , Agricultural laborers -- South Africa -- Eastern Cape -- Social conditions , Agricultural laborers -- South Africa -- KwaZulu-Natal -- Social conditions , Agricultural laborers -- Legal status, laws, etc. -- South Africa -- Eastern Cape , Agricultural laborers -- Legal status, laws, etc. -- South Africa -- KwaZulu-Natal , Apartheid -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3366 , http://hdl.handle.net/10962/d1011978 , Agricultural laborers -- South Africa -- Eastern Cape , Agricultural laborers -- South Africa -- KwaZulu-Natal , Agricultural wages -- South Africa -- Eastern Cape , Agricultural wages -- South Africa -- KwaZulu-Natal , Eastern Cape (South Africa) -- Rural conditions , KwaZulu-Natal (South Africa) -- Rural conditions , Agricultural laborers -- South Africa -- Eastern Cape -- Social conditions , Agricultural laborers -- South Africa -- KwaZulu-Natal -- Social conditions , Agricultural laborers -- Legal status, laws, etc. -- South Africa -- Eastern Cape , Agricultural laborers -- Legal status, laws, etc. -- South Africa -- KwaZulu-Natal , Apartheid -- South Africa
- Description: This thesis examines the agricultural labour process on commercial farms in post-apartheid South Africa with a particular focus on systems of labour control on these farms. Considerable literature exists about the labour process in capitalist society but the capitalist labour process does not exist in any pure form. Rather, different labour processes exist and the specific form they take depends on spatial and temporal conditions. Additionally, labour processes are often economic sector-specific. Because of variation in capitalist labour processes, differences in systems of labour control (or labour control regimes) also arise. Historically, up until the end of apartheid in 1994, the labour control regime on commercial farms in South Africa was marked by a paternalistic despotism of a racialised kind. This in part reflected the fact that commercial farms were simultaneously sites of both economic production and social reproduction and, further, they were very privatised agrarian spaces largely unregulated (specifically with regard to labour) by the state. Since the end of apartheid, commercial farms have been subjected to multiple pressures. Notably, the South African state has strongly intervened in labour relations on commercial farms, and commercial farms have been subjected to ongoing neo-liberal restructuring. This has led to the prospects of changes in the prevailing labour control system on commercial farms. In this context, the thesis pursues the following key objective: to understand changes and continuities in the labour process on commercial farms – and particularly labour control systems – subsequent to the end of apartheid in South Africa. It does so with reference to four farms in Eastern Cape and KwaZulu-Natal Provinces.
- Full Text:
- Date Issued: 2014
- Authors: Kheswa, Nomzamo Sybil
- Date: 2014
- Subjects: Agricultural laborers -- South Africa -- Eastern Cape , Agricultural laborers -- South Africa -- KwaZulu-Natal , Agricultural wages -- South Africa -- Eastern Cape , Agricultural wages -- South Africa -- KwaZulu-Natal , Eastern Cape (South Africa) -- Rural conditions , KwaZulu-Natal (South Africa) -- Rural conditions , Agricultural laborers -- South Africa -- Eastern Cape -- Social conditions , Agricultural laborers -- South Africa -- KwaZulu-Natal -- Social conditions , Agricultural laborers -- Legal status, laws, etc. -- South Africa -- Eastern Cape , Agricultural laborers -- Legal status, laws, etc. -- South Africa -- KwaZulu-Natal , Apartheid -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3366 , http://hdl.handle.net/10962/d1011978 , Agricultural laborers -- South Africa -- Eastern Cape , Agricultural laborers -- South Africa -- KwaZulu-Natal , Agricultural wages -- South Africa -- Eastern Cape , Agricultural wages -- South Africa -- KwaZulu-Natal , Eastern Cape (South Africa) -- Rural conditions , KwaZulu-Natal (South Africa) -- Rural conditions , Agricultural laborers -- South Africa -- Eastern Cape -- Social conditions , Agricultural laborers -- South Africa -- KwaZulu-Natal -- Social conditions , Agricultural laborers -- Legal status, laws, etc. -- South Africa -- Eastern Cape , Agricultural laborers -- Legal status, laws, etc. -- South Africa -- KwaZulu-Natal , Apartheid -- South Africa
- Description: This thesis examines the agricultural labour process on commercial farms in post-apartheid South Africa with a particular focus on systems of labour control on these farms. Considerable literature exists about the labour process in capitalist society but the capitalist labour process does not exist in any pure form. Rather, different labour processes exist and the specific form they take depends on spatial and temporal conditions. Additionally, labour processes are often economic sector-specific. Because of variation in capitalist labour processes, differences in systems of labour control (or labour control regimes) also arise. Historically, up until the end of apartheid in 1994, the labour control regime on commercial farms in South Africa was marked by a paternalistic despotism of a racialised kind. This in part reflected the fact that commercial farms were simultaneously sites of both economic production and social reproduction and, further, they were very privatised agrarian spaces largely unregulated (specifically with regard to labour) by the state. Since the end of apartheid, commercial farms have been subjected to multiple pressures. Notably, the South African state has strongly intervened in labour relations on commercial farms, and commercial farms have been subjected to ongoing neo-liberal restructuring. This has led to the prospects of changes in the prevailing labour control system on commercial farms. In this context, the thesis pursues the following key objective: to understand changes and continuities in the labour process on commercial farms – and particularly labour control systems – subsequent to the end of apartheid in South Africa. It does so with reference to four farms in Eastern Cape and KwaZulu-Natal Provinces.
- Full Text:
- Date Issued: 2014