Landmines pose a significant risk to the health and livelihood of millions of people in war-torn countries. From a humanitarian point of view, these hidden dangers must be detected and removed. Several detection methods exist, including ground-penetrating radar, sniffer dogs and rats. It is a tedious process and can take months to clear only a single minefield. This study investigates whether TNT from leaking landmines can be detected using hyperspectral remote sensing of plant foliage, with the aim of being an area reduction aid. Increasing concentrations of TNT was administered to a study sample of five species of trees, five species of grasses and four species of shrubs, and leaf-clip readings were taken at regular intervals with a field spectrometer. Statistical correlation testing of seven plant health indices (red-edge position, first derivative reflectance, normalised difference water index, moisture stress index, water band index, photochemical reflectance index and nitrogen index) was done on the results of the readings. TNT has a mixed effect on the health of the tested plants, with some species displaying adverse effects of TNT on their health, while others proved to be healthier or more resilient against the effects. Results also varied in magnitude. Even in a single species, differing concentrations TNT lead to varying results. The various indices delivered varying results, with some indices delivering inconclusive results. Positive results were yielded from the REP analysis, indicating this as a possible index to use in landmine detection. / Dissertation (MSc)--University of Pretoria, 2017. / Geography, Geoinformatics and Meteorology / MSc / Unrestricted

Beef production is known to be the most important livestock related activity in Namibia (Just over 2 million cattle in Namibia in 2009) with the majority of weaners being exported to the South African feedlot industry. Extensive beef production requires a sound knowledge of management practices, genetics and nutrition. The nutritional requirements of cattle remain one of the most important factors for maximizing return and profitability of the farming enterprise. The purpose of this study was to quantify the nutritive value of two veld types in the north western part of Namibia. The thorn bush savanna was assigned as treatment K whilst the mopane savanna was assigned as treatment M. For the oesophageally collected samples there were differences between the two years (2007 and 2008) for all the parameters as well as differences between the two veld types (treatments) and periods. Crude protein (CP) had a large seasonal variation in both treatments, with treatment K having higher CP concentrations for the majority of the trial period compared to treatment M. Phosphorous (P) also tended to show seasonal variation with higher concentrations during the wet season. The CP requirements for a 400kg cow were not met during the time when the cow is expected to be pregnant, however during lactation and early gestation the CP requirements of a 400kg cow are met from the intake of forage alone. The P requirements of a 400kg cow were met during the majority of the year except during the last trimester of gestation where the forage alone is not able to supply the P requirements of a 400kg cow. Treatment K had higher concentrations of calcium (Ca), zinc (Zn) and copper(Cu) compared to treatment M, whilst Treatment M had a higher concentration of manganese (Mn) during the majority of the trial period. The Mn concentration of the forage was shown to be adequate during most parts of the year and was able to supply the Mn requirements of a 400kg cow during gestation and lactation for both treatments. However, Cu, Zn and Mg were deficient especially during the winter months and intake from forage alone was not able to supply the Cu, Zn and Mg requirements for a 400kg cow during both gestation and lactation. The Ca concentration of both treatments was high, and caution should be taken to ensure that the high intake levels of Ca through feed and water do not cause mineral imbalances. The in vitro digestible organic matter (IVDOM) concentrations increased from the winter to the summer months. The neutral detergent fibre (NDF) and acid detergent lignin (ADL) concentrations varied between treatments as well as throughout the trial period. The rumen cannulated animals showed differences between years, treatments and periods for total volatile fatty acid (VFA) concentration and rumen NH3-N. The rumen ammonia-N concentrations increased during the periods of higher rainfall whilst the total VFA concentration showed no distinct seasonal pattern. The faecal CP results indicated that protein supplementation is necessary especially during periods of lower rainfall. whilst the faecal P results fell within the normal range. The relationship between faecal CP and diet CP concentration was not so strong and faecal CP concentration should be used with caution to predict the CP concentration of the forage. The relationship between faecal P and diet P concentration was also not strong when both treatments and years were combined which confirms that such relationships need to be tested under specific conditions. / Dissertation (MSc (Agric))--University of Pretoria, 2018. / Animal and Wildlife Sciences / MSc (Agric) / Unrestricted

The study investigated Eastern and Western tourists’ luxury value perceptions regarding exotic leather products, the e-luxe value perceptions that drive their preference for specific attributes of an exotic leather product’s social media presence and the influence this has on their purchasing intent. A survey was conducted that focused on American and Chinese luxury consumers and was facilitated by an international independent company, Qualtrics. Qualtrics assisted with collecting the data by means of a non-probability convenient sampling method. Online questionnaires were distributed to consumers on their data basis and 1043 usable questionnaires were collected, of which 525 were from Chinese respondents (translated to Cantonese and Mandarin) and 518 were from American respondents. The statistical analysis that was conducted consisted of descriptive statistics, factor analysis, Levene’s test of equality of variance and Pearson’s Correlation Coefficient. The demographic and consumer behaviour findings assisted in better understanding the Eastern and Western tourist. The study’s findings showed that almost all of the respondents were aware that South Africa is known for its exotic crocodile and ostrich leather. Most of the respondents fell in the millennial age group. The most common type of purchase made by Americans were accessories for themselves, while the Chinese rather purchased souvenirs on their trips. Chinese respondents mostly used Blogs, while Americans preferred to use Facebook, to gain information. This study also showed that the luxury value perceptions might be different between cultural groups. Both the groups conceptualised their luxury value perceptions completely different to what previous literature states. Two luxury value perceptions could be identified for the American respondents, namely “Me” value and Financial value, while there were three luxury value perceptions for the Chinese respondents, namely “Pleasure” value, Social value and Financial value. This difference in the luxury value perceptions was also evident in the respondent’s e-luxe value perceptions. The self-developed scale based on the values of e-luxe model showed that both groups also conceptualised their e-luxe values differently. The two e-luxe value perceptions identified for the Americans were “American Experience” e-luxe value and “Perceived Me” e-luxe value. The two e-luxe values that could be identified for the Chinese respondents were “Chinese Experience” and “Price”. The study also found that both the groups expressed very strong purchasing intentions for exotic leather products with no significant difference between the two groups. The results also showed significantly strong positive correlations between American respondents’ “Me” and Chinese respondents’ “Pleasure” luxury value perceptions, and their purchasing intent. Significantly strong positive correlations were also seen between American respondents’ “American Experience” and Chinese respondents’ “Chinese Experience” luxury value perceptions, and their purchasing intent. This serves as a guide to South African and international retailers and marketers to position their exotic leather products in such a way that it communicates important luxury values to international tourists and thereby influences their purchasing intent in a positive way. / Dissertation (MConsumer Science)--University of Pretoria, 2017. / Consumer Science / MConsumer Science / Unrestricted

The state of the current national agricultural capital input account is arguably misleading in measuring capital input use in South Africa. This is attributable to the problems associated with measurement of capital inputs, as well as changes in methodologies of different sources of capital data. This study questions the current state of national capital input accounts, with specific reference to machinery and implements, and a specific focus on tractors. It corrects the input series by revising the value of tractor sales and the machinery and implements series component of the capital input account for the South African agricultural sector, using more robust assumptions and underlying data as far as possible. This study shows that the current South African national capital input account is understated and resultantly has knock-on effects on service flows and agricultural productivity estimates for South Africa. Amongst other measurement problems in the capital formation series of South Africa, is the failure to incorporate quality adjustments in the valuation of capital. This measurement problem has been shown to lead to undercounting and effectively flawed productivity estimates. This study analyses the impact of incorporating quality changes in valuing tractors and using disaggregated data as far as possible. As such, this study focuses on tractor use in South Africa and analyses the tractor input by disaggregating the tractor categories and attributes. The tractor attributes and other drivers, such as net farming income and area planted in hectares, are used to trace the evolution of tractorisation in South Africa. As such, this study shows how tractorisation has changed over time and incorporates these quality changes by disaggregation, using underlying price and quality data for tractors in different classes and types. The assumptions used in past analyses have resulted in a failure to explain the evolution that has taken place in input use in the face of tractorisation innovation. The current Abstract estimates of the tractor price index are not cointegrated with the rand dollar exchange rate and net farm income, which is not in line with economic theory. In addition, current tractor trends fail to reflect the macro-economic trends that have taken place in South African agriculture. As such, the corrected capital input series will contribute to the understanding of economic trends in tractorisation and contribute to the labour debate in South Africa at an aggregate level. Thus, besides having a direct impact on service flow estimates and ultimately productivity analysis, this study has other agricultural policy impacts, such as on trade, mechanisation policy, and R&D policy, as well as on tax policies in the sector. For machinery manufacturers, this study is important in that it provides sound estimates of the relationship between tractor prices and other variables, which are useful for making informed business decisions. This study illustrates the effects of flawed measurement of inputs that impacts policy analysis and recommendations. / Thesis (PhD)--University of Pretoria, 2018. / Agricultural Economics, Extension and Rural Development / PhD / Unrestricted

objective of the study is to investigate the economic important performance traits of beef cattle bulls in a production environment. Performance data was collected, from 2001 to 2012 on 1318 bulls comprising of four breeds [Beefmaster (n = 447), Bonsmara (n = 342), Braford (n = 202) and Nguni (n=327)], from the Eastern Free State Veld Bull Club (EFSVC). Bulls were evaluated on performance traits at the farm Paardenplaats over a period of between 155 to 227 days. Bulls arrived in the first week of September. The composite breeds started and finished the performance evaluation period heavier (P < 0.05) than the Nguni (NG) bulls each year throughout the study period. While the Beefmaster (BM) bulls showed higher (P < 0.05) initial live weight (ILW) and final live weight (FLW) than both the Braford (BF) and Bonsmara (BO) bulls in some of the years during the study period. The BM (723 g/day ± 5.4) and BF (724 g/day ± 8.0) bulls had higher (P < 0.05) average daily gain (ADG) than the BO (699 g/day ± 6.1) bulls. All three composite breeds had higher (P < 0.05) ADG than the NG (633 g/day ± 6.9) bulls. However the NG (8.94 ± 0.071) bulls were more efficient (P < 0.05) in terms of Kleiber ratio (KR) compared to the BO (8.36 ± 0.062), BF (8.35 ± 0.082) and BM (8.22 ± 0.055) bulls. The BM (33.51 cm ± 0.125) bulls had larger (P < 0.05) scrotal circumference (SC) than the BO (32.79 cm ± 0.146) bulls. While the BM, BO and BF (33.19 cm ± 0.189) bulls had larger (P < 0.05) SC than the NG (30.30 cm ± 0.170) bulls. In addition the NG (10.38 % ±0.059) bulls had larger (P < 0.05) SC as a percentage of FLW than the BO (9.09 % ± 0.051), BF (8.70 % ± 0.066) and BM (8.63 % ± 0.044) bulls. The NG (138.31 cm2 ± 1.832) bulls had a smaller (P < 0.05) pelvic score (PS) than the BF (160.20 cm2 ± 1.694), BO (161.30 cm2 ± 1.376) and BM (164.16 cm2 ± 1.256) bulls. However, the NG (49.62 % ± 0.592) bulls had higher (P < 0.05) PS as a percentage of FLW than the BO (45.52 % ± 0.444) bulls, while both these breeds had higher (P < 0.05) values compared to the BM (43.43 % ± 0.406) and BF (42.77 % ± 0.547) bulls. The composite breeds had higher (P < 0.05) body condition scores (BCS) at the start of the performance evaluation than the NG bulls, with no difference (P > 0.05) at the end of a specific year. The NG bulls had a lower (P < 0.05) hair coat score (HCS) than the composite breeds. Variation for both muscle score (MS) and temperament score (TS) was observed between the breeds. Auction prices were only available from year 6 until year 12. Over the performance evaluation period a linear increase in the weaner price was observed as the price for yellow maize increased (P < 0.05; R2 = 0.52), and as the weaner price increased there was a linear increase in the price obtained for the BF bulls on the auction (P < 0.05; R2 = 0.73). However, no regression (P > 0.05) fitted the data between the prices received for the BF bulls on the auction and the yellow maize price. In year 9 a linear (P < 0.05; R2 = 0.45) and quadratic (P < 0.05; R2 = 0.57) regression fitted the data between ADG and the auction prices received for the BF bulls. A quadratic regression (P < 0.01; R2 = 0.97) fitted the data between the auction prices received for the BO bulls and the KR values for the BO bulls in year 9. In year 11 a linear regression (P < 0.05; R2 = 0.24) fitted the data between the auction prices received for the BM bulls and their KR values in year 11. In year 6 the auction prices received for the BO bulls increased linear (P < 0.05; R2 = 0.27) as their MS increased and in year 9 a quadratic regression (P < 0.01; R2 = 0.99) fitted the data for these two parameters. In year 7 a linear (P < 0.01; R2 = 0.50) and quadratic (P < 0.01; R2 = 0.56) regression fitted the data between the auction prices received for the BM bulls and their MS. In year 10 a linear (P < 0.01; R2 = 0.39) and quadratic (P < 0.01; R2 = 0.44) regression fitted the data between the auction prices received for the BM bulls and their SC. The auction prices received for the BO bulls increased linear (P < 0.05; R2 = 0.35) as their SC increased in year 11. This study is evidence that there exist variation within breed as well as between breeds. Therefore, commercial farmers should pay attention to these production parameters when selecting a sire in order to improve the genetic potential of their herd. / Dissertation (MSc (Agric))--University of Pretoria, 2017. / Animal and Wildlife Sciences / MSc (Agric) / Unrestricted

The aims of this research thesis are to synthesise VO2, V2O5 and V6O13 nanostructures and apply the materials on sensor electrodes for gas and humidity sensing. These materials were synthesised and optimised using chemical vapour deposition (CVD), microwave assisted and pulse laser deposition (PLD) techniques. Analyses with thermogravimetric (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), Raman and Fourier transform infrared (FTIR) spectroscopy showed VOx phases order as NH4VO3 ? VO2 + V2O5 (150 – 200 °C) ? V6O13 (300 °C) ? V2O5 (above 350 °C). This is when the precursor NH4VO3 was annealed in CVD between 100 – 350 °C in H2 atmosphere for 2 hrs. Adsorption analysis of VOx nanostructures showed a profile of Brunauer-Emmett-Teller (BET) surface areas which increased with the annealing temperature until 300 °C after which the transition occurred. Humidity (%) sensing response of VOx showed high response for V6O13 and V2O5 phase whereas, the Langmuir isotherm plot in the form of the response per BET surface area with respect to different levels of relative humidity showed high response for VO2. Phase evolution diagram based on these properties has been proposed. Thermal CVD annealing of NH4VO3 at 500 °C in N2 atmosphere for 2, 12 and 24 hours produced monoclinic V6O13 (at 2 hrs) and ?-orthorhombic V2O5 (at 12 and 24 hrs) nanorod structures using the above characterization techniques. Gas sensing application of these structures revealed that the H2S gas is selective in adsorption to V6O13 phase with 132 % response magnitude at 350 °C and 60 ppm, this response is 647.2 % higher than that of NH3, CH4, NO2, H2 and CO. The response and recovery times are 32 and 129 s respectively which is remarkably short compared with the data in literatures. This V6O13 sensor was ranked with its V2O5 counterpart and still found to be 238.5 % higher for H2S gas. Density functional theory (DFT) through ab initio molecular dynamics of (110) facet of monoclinic V6O13 and ?- orthorhombic V2O5 also showed high H2S adsorption energy for V6O13 than V2O5 with a profile which simulate the experimental findings. Low temperature microwave assisted synthesis of VOx from NH4VO3 without post-annealing treatment demonstrated small size homogeneous crystallite with high BET surface area and high adsorption and desorption pores. These properties translated to sub-ppm room temperature sensing of the flammable CH4 and odorant NH3 and toxic NO2 with high sensitivity. The VO2 (B) phase produced via the same microwave process applied for humidity sensing in the lateral gate metal oxide semiconductor field effect transistor (MOSFET) configuration for 0, 5, 8, 10, 12 and 15 V gate voltages. An optimum percentage humidity response observed at 5 V showed response and recovery times in the order of 60 – 70 s which is remarkably shorter than the ? 300 s response of the non-gated VO2 humidity sensor reported in this thesis. Statistical information extracted from the non-linear S-curve Hill Dose rate showed that the VO2 (B) sensor is very resilient to relative humidity by showing the humidity level of more than 100% where the response of the sensor could be reduced to 50%. In-situ Raman spectroscopy sensing of NH3 gas at the surface of PLD deposited V2O5 thin film was presented. The film crystal structure, depth profile and oxidation state was studied by cross section scanning electron microscope (SEM), time of flight secondary ion mass spectroscopy (TOF-SIMS), XPS and group theoretical analysis. Recoverable red shift of 194 cm-1 and blue shift of 996 cm-1phonons upon the interaction with the NH3 gas at 25 and 100 °C was observed. Decrease in the Raman scattered photons of the 145 cm-1 phonon was also observed for different levels of NH3 exposure. The responses of these phonon properties in NH3 environment compared to the chemoresistive sensing of the film at 40 ppm showed that the in-situ Raman spectroscopy techniques is not only more sensitive but also demonstrated possibility for selective gas detection via blue and red shift of phonon frequencies. / Thesis (PhD)--University of Pretoria, 2017. / Physics / PhD / Unrestricted

This study pursued the following three objectives: (1) to test the presence of Asymmetric Price Transmission (APT) among integrated wholesale maize markets during the post-agricultural market liberalisation period from July 2004 to March 2016; (2) to understand the influence of government interventions on the performance of maize and wheat grain markets; and (3) to examine the effect of domestic supply and demand dynamics on the maize market using a partial equilibrium modelling framework. In pursuit of the first objective, this study estimated an Asymmetric Vector Error Correction Model (AVECM). Findings from the inter-regional maize market integration analysis indicated that all maize market pairs considered in this study were cointegrated with the central Addis Ababa wholesale maize market. Spatial maize market integration has not only improved, but there has been an improved complete pass-through of price signals, with no evidence of positive APT in the regional wholesale maize markets in Ethiopia. Despite the widely held belief by consumers and government that traders’ inappropriate price adjustment contributes to the persistence of soaring food prices in Ethiopia, we found no evidence to support this argument. Instead, wholesale maize traders tend to adjust homogenously to increases and decreases in maize price deviations from the central Addis Ababa maize market. Hence, the widely held perception that considers traders as constituting a main contributor to the recent soaring food price situation in Ethiopia is just a misconception. In this study, it is argued that the recent surge in grain prices in Ethiopia has little to do with APT in maize markets. The second objective employed a regime-dependent Vector Error Correction (VECM) model to examine the extent of the integration of Ethiopian wheat and maize markets with the world market and the effect of policy interventions on the spatial integration of food markets. Findings of the cointegration analysis indicate that domestic wheat and maize markets are strongly integrated with the world market during a period in which the government intervenes, as opposed to periods of low intervention. Despite the presence of a long-run relationship and absence of APT, domestic wheat prices are distorted by the government’s secretive and unplanned interventions. Domestic wheat prices have surpassed the ceiling price during periods of heavy government interventions (i.e. since 2008). We argue that the increasing price gap between domestic and world wheat markets since 2008 is due to trade flow restrictions caused by foreign exchange rationing and subsidised wheat distribution. A single commodity partial equilibrium approach was used to investigate the maize price formation and a likely impact of a bumper harvest and drought shocks on the maize market. Findings from the behavioural equations reveal that farmers respond very little to price in planning their maize acreage. Rather, the analysis demonstrated that rainfall and technological progress were relatively more important for higher maize acreage growth. Regarding the supply side shocks (a bumper harvest and drought) on maize prices, we found that a 20 per cent increase in maize yield could reduce nominal maize price by 81 per cent. This implies a decrease in maize price level of 238 per cent (110 USD/t) below the export parity price. This makes maize exports profitable, and shifts the trade regime from autarky to an export parity regime. On the other hand, the effect of drought could increase maize prices by 61 per cent in the short run (within the year). The effect could result in the domestic wholesale maize price moving over the upper threshold import parity price by 46 per cent (126 USD/t). As a result, maize imports would become profitable. / Thesis (PhD)--University of Pretoria, 2017. / Agricultural Economics, Extension and Rural Development / PhD / Unrestricted

Glyphosate was patented as a broad-spectrum, non-selective, systemic herbicide in 1974. In 1996, glyphosate-resistant Lolium rigidum (rigid ryegrass) was reported in Australia. Since then 34 other weeds the world over have evolved resistance to this herbicide. The first case of glyphosate resistance in South Africa was in rigid ryegrass in vineyards. Resistance to glyphosate in Conyza bonariensis (L.) Cronquist (flax-leaf fleabane) was reported in 2003 in the Breede Valley, Western Cape. Glyphosate resistant Conyza canadensis (horseweed fleabane) reportedly becomes sensitive at low temperatures (below 12 oC). If the resistance mechanism is vacuolar sequestration, low temperatures will prevent glyphosate to be translocated into the vacuole. Tank mixtures with foliar manganese and other foliar-applied nutrient elements, in particular cations such as Mn2+, Zn2+, Fe2+, etc, are known to decrease glyphosate efficacy. The aim of the present study is to determine if growth stage has an influence on glyphosate tolerance in C. bonariensis, if highly glyphosate-tolerant C. bonariensis plants become sensitive at low temperatures, and to assess if there is an effect between high manganese levels and response to glyphosate, as well as if mancozeb (fungicide containing Mn and Zn) influences the glyphosate-manganese interaction. C. bonariensis seed was collected at 12 locations. At the four to six leaf stage six dosages of glyphosate was applied: 0, 0.25, 0.5, 1, 2 and 4 times the recommended dosage (2 L ha-1 Roundup Turbo). Fresh mass were measured at 21 days after treatment (DAT). Data was subjected to ANOVA. GR50 and Resistant / Sensitive values were calculated. From the screening experiment two highly tolerant, two tolerant and two susceptible populations were identified. The growth stage experiment was conducted in the exact same manner as the screening experiment, with growth stage as an added factor. Plants were treated with glyphosate at two different growth stages (10 – 12 and 16 – 20 leaves). A second screening experiment with four populations from the same area was performed. Plants from a highly tolerant population were grown in the greenhouse up to the four leaf stage and then moved to the temperature gradient table. Plants were exposed to temperature ranges of 8 - 13 oC, 15 - 20 oC and 22 - 27 oC, respectively. Plants were treated with glyphosate at 0, 0.5, 1, 2 and 4 times the recommended dosage and fresh mass measured at 21 DAT. The manganese experiment had three factors: manganese level, location and glyphosate dosage. Seed from a sensitive and highly tolerant population were planted in a seeding tray. Seedlings were transplanted to a hydroponic system containing three different nutrient solutions with different manganese levels. Plants were treated with glyphosate at the 4-6 leaf stage at 1 and 2 times the recommended dosage. The rest of the materials and methods are the same as for the temperature experiment. The final experiment was performed to examine if mancozeb has an influence on the efficacy of glyphosate when applied to C. bonariensis. Mancozeb was applied before and after glyphosate to susceptible C. bonariensis plants. For two of the populations in the screening experiment all of the replicates survived the recommended dosage, and hence, they were classified as highly tolerant. Two other populations were classified as tolerant and two as sensitive. There is a clear difference in the sensitivity of the various populations to glyphosate as well as populations from the same area. These six populations were further used in the growth stage experiment where the same results were obtained regarding the sensitivity of the populations at the 10 - 12 leaves growth stage. Plants at the 16 – 20 leave growth stage are much more tolerant to glyphosate. The second screening experiment showed that C. bonariensis plants from the same area differ in the tolerance towards glyphosate. Highly glyphosate-tolerant plants did not become susceptible at a low temperature. Susceptibillity to glyphosate increased at the higher temperatures. Therefore, vacuolar sequestration is probably not the mechanism of resistance responsible for the high tolerance to glyphosate. There was no replication of manganese treatments in the manganese experiment and therefore differences could not be tested. The unique methodology employed in this experiment is, however, of value. Mancozeb did not have an influence on glyphosate efficacy when applied either before or after glyphosate. If resistance to glyphosate develops in C. bonariensis and in other species on a wider scale than is currently the case in South Africa it will be a big problem for farmers in various cropping systems. Therefore, the label must be followed very strictly to ensure that plants are treated at the correct dosage and growth stage to ensure that populations are not incorrectly referred to as resistant. / Dissertation (MSc (Agric))--University of Pretoria, 2017. / Plant Production and Soil Science / MSc (Agric) / Unrestricted

One of the global and most economically significant viral disease of grape cultivation is grapevine-leafroll disease (GLD). Viruses associated with GLD are known as grapevine leafroll associated viruses (GLRaVs) and numbered in order of discovery, with the most important one being GLRaV-3. Viti- and Foveaviruses are often also often found in mixed infections with GLD, and speculation exists regarding a codependence of transmission of some Vitiviruses with GLRaV-3. As with most grapevine growing countries, many strains of GLRaVs, Viti- and Foveavirus are present in South Africa. A local certification scheme exists with the objective of providing grapevine scion and rootstock material free of these viruses to farmers. Rootstocks show no GLD symptoms thus making visual diagnostics impossible. Furthermore, it is generally accepted that GLRaV-3 is difficult to test for in rootstocks than in scions, possibly due to uneven distribution and low viral titre in rootstocks. It is however also possible that rootstocks select for specific strains of GLRaV-3 which may be less amenable to the detection technique. The difficulty in detection of GLRaV-3 could result in unwitting infection of healthy scion material by infected rootstock material during grafting. To gain greater insight into the detection of GLRaV-3 detection in rootstocks both rootstock and scion tissue were sampled separately from 95 grapevine individuals and tested using a broad spectrum PCR protocol directed at a highly conserved primer binding sequence flanking a highly variable region of the GLRaV-3 helicase gene. Amplicons of scion and rootstocks of 22 vines were subjected to Illumina next generation sequencing to determine the composition of the GLRaV-3 variant population. Poor detection (43% of samples) at low amplicon levels were obtained for GLRaV-3 in primarily R99 rootstock compared to the corresponding scions (GLRaV-3 detected in 93% of the scions samples) and corroborated the perceived poor detection of this virus in at least R99. We also determined that poor detection of GLRaV-3 is not due to the presence of a PCRinhibitory substance in rootstocks as we obtained high levels of amplicons of Vitiand Foveaviruses associated with the rootstocks of GLD infected vines. This was achieved using universal degenerate primer nested RT-PCR combined with Illumina next generation sequencing of the resulting amplicons. Confirmation tests were performed using Vitivirus specific primers to determine the identity of the unidentified Viti- and Foveaviruses found. Direct Sanger sequencing was used on 37 rootstock samples and 20 corresponding scion samples. Viti- and Foveaviruses were significantly less detected (61%) in rootstocks than corresponding scions (82%). The dominant component of the viral population was shown to differ between samples, with Grapevine virus B (GVB) and Grapevine rupestris stem pitting associated virus (GRSPaV) only found dominant in rootstocks. NGS data exhibited that the largest amount of the total reads belonged to GVB (44%), though no pattern could be differentiated between differing rootstocks. This is the most comprehensive study done on the viruses associated with GLD in rootstocks in South Africa, and will contribute to improve the certification scheme. / Dissertation (MSc)--University of Pretoria, 2017. / Microbiology and Plant Pathology / MSc / Unrestricted

Due to tighter financial margins, the need for better knowledge of grade data is required. Geological models allow the user to have a better understanding of the geological environment in which mining is taking place. Three dimensional (3D) geological, ore deposit, and mining models are therefore becoming increasingly important in the mining industry. 3D models are being used more frequently for mineral potential targeting, as well as resource assessment, because good quality geological models allow the user to determine grade domains within mineralized environments. The aim of this thesis is to create a geological model for Leeuwpoort Tin Mine (C-Mine) and test the applicability of this 3D model for exploration purposes. The 3D geological and interpolant models created of Leeuwpoort Mine was used to determine the probability of intersecting a lode of economic interest, if 500 drillholes were randomly drilled in a specific boundary. Resampling was conducted using the Bootstrap method, in order to determine how the probability will change as different borehole sample sizes are used. When conducting a quantitative resource assessment of mineral deposits, grade-tonnage models form a fundamental part in the estimation and prediction process. Grade and tonnage models are used during quantitative resource assessment to predict the values of the known deposits for a specific type, and can also be used to determine the potential value of undiscovered deposits in a specific area. If sufficient geological data is available, the tonnage of mineralized bodies can be calculated and a grade-tonnage model can be created from the 3D geological model. 3D models can be used as a summary and visualization tool for geological environments. The 3D visualization of deposit give a much better representation of the orebody than 2D cross-sections from a few drillholes. The effectiveness of 3D model, as a possible tool for mining, is limited by the quality and quantity of the data. Poor quality data will result in poor quality models, whereas limited data will result in a higher level of uncertainty of the estimates based from these 3D models. However, even limited data can be used to visualize geological environments. In the case of Leeuwpoort Mine, limited structural and lithological information was available to create the 3D models. However, the provided peg index noted the positions of the mine pegs, and consequently indicate where the lodes were mined. In this instance, with limited mine peg data, the lode “volumes” could be reconstructed. The peg index was used to delineate the mining area in order to model the lodes, as well as interpret geological features. Once the lode “volumes” were created in the 3D model, the specific orezone with the geometric relationship between individual lodes of Leeuwpoort Mine could be defined. In addition, the probability of intersecting a certain number of lodes was derived from these modelled surfaces, resulting in the estimation for the predicted probability of success. The 3D geological and interpolant models created of Leeuwpoort Mine were used to determine the probability of intersecting a lode of economic interest, if exploration drilling were to be done. Resampling was conducted using the Bootstrap method, in order to determine how reliable this prediction is as a function of number of boreholes. The results obtained from the Bootstrap analysis indicates that the average probability of intersecting a lode of economic significance, for each of the different sample sizes stays the same. A higher level of confidence in the probability of intersecting a lode can be assumed for areas that have large quantities of drilling. If a geological environment similar to that of Leeuwpoort Mine is considered for an exploration project, the chances of intersecting an economical orebody or lode during exploration is very low. When considering Greenfields exploration (virgin exploration), the chances of intersecting a mineralized body is extremely low, and a lot of money has to be invested to obtain meaningful results. However, if Brownfields exploration (exploration on a known area) takes place, the chances of intersecting a mineralized body is higher, because prior knowledge of the area exists and can be used to make informed decisions on where to drill. Less money needs to be invested for the drilling than for Greenfields exploration. In the case of Leeuwpoort Mine, unfortunately even Brownfields exploration will bear a very limited chance of identifying a mineralized body, which means that in such a scenario, the information about potential success rate of a drilling program is even more important for drilling and financial planning. / Dissertation (MSc)--University of Pretoria, 2017. / Geology / MSc / Unrestricted