A preliminary study on the effects of elevated CO2 on aphid resistance of Tugela Dn and the population dynamics of the Russian wheat aphid (Homoptera: Aphididae), Diuraphis noxia
- Authors: Mundondo, Daphine
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Biochemistry)
- Identifier: vital:11402 , http://hdl.handle.net/10353/d1020244
- Description: Food security is of major importance due to the increasing world population with 8.9 billion people expected by 2050 (Cohen, 2003). Diuraphis noxia (RWA), have caused aggravating, massive losses to wheat farmers in many areas of the world. If unchecked, RWA are able to destroy plants resulting in major economic impacts (Botha, 2013). Due to ineffective use of other control methods, the Small Grains Institute in Bethlehem, South Africa, have therefore developed resistant cultivars to the known RWA subtypes over the past decades through intensive breeding programmes (Tolmay et al., 2006). Climate change has however become a major factor threatening food security especially with the observed increase in CO2 from less than 300 ppm in pre-industrial period to the current 385 ppm and is predicted to reach 550 ppm by 2050 (IPCC, 2007; Meehl et al., 2007). Elevated CO2 concentration may affect individual species of a community hence the need to understand the wheat-aphid interactions. In this study, population growth rates and virulence of RWA SA1 at ambient (385 ppm) and elevated (450 ppm) CO2 concentration were evaluated on two wheat cultivars: Tugela Dn (resistant) and Scheepers (susceptible). Fluorescence microscopy techniques using aniline blue were used to investigate feeding related damage caused by RWA SA1 through an examination of callose deposition at the two CO2 concentration. A two-dimensional gel electrophoresis method was developed in order to determine the effect of RWA SA1 on the wheat cultivars proteome at the two CO2 concentration. Differentially expressed proteins that were up or down regulated more than two fold were identified using PDQuestTM Basic 2D Gel analysis software. Populations of RWA SA1 increased significantly on the two wheat cultivars at both CO2 concentration. Although the population growth rate for RWA SA1 on both cultivars was generally exponential at all treatments, growth at elevated CO2 concentration was noticeably faster with populations increasing 3 fold in 14 days as compared to the 2 times at ambient CO2 concentration. Hence, both cultivars provided a better quality host for RWA SA1 at 450 ppm than 385 ppm. There was no significant difference between RWA SA1 population on Tugela Dn and on Scheepers at elevated CO2 concentration on day 14 after infestation which means there was a change in the resistance mechanism in Tugela Dn at this condition. Approximately 70% of the total leaf showed chlorosis by 21 days of aphid infestation for both cultivars although the susceptible cultivar was more vulnerable. There was low callose deposition in the controls (uninfested plants) but heavy callose in infested plants due to aphid feeding. A proteomics approach was used as a pilot study to investigate whether it would be possible to identify the changes in the resistance mechanism during aphid infestation under elevated CO2 levels. The major changes in the proteome of the control group (uninfested Tugela Dn at ambient versus elevated CO2 concentration) occurred in the early events (day 1-7) in the molecular weight range of approximately 25 kDa to 55 kDa are mainly within the basic to neutral pH range. This was suggested to be a result of mechanisms to adjust to the CO2 concentration. Elevated CO2 results in instant higher photosynthetic rates and C:N ratios as well as changes in expression levels of SA-dependant defense genes (Lindroth 1995; Hughes and Bazzaz, 2001; Sun et al., 2013). Because most of these changes are directly regulated by proteins, it is expected that the most differential protein expression will occur immediately after the atmospheric changes (early events) as was shown in the study. Infested plants under elevated and ambient conditions showed that the stress conditions gave rise to differentially regulated proteins within the wheat proteome. Most changes occurred elevated CO2 levels. It can be suggested that the changes were a result of differentially regulated plant defence proteins which fall in this range (25 kDa - 80 kDa) such as peroxidases, chitinases and β-1.3-glucanases as well as protein kinases, heat-shock proteins and photosynthetic proteins. These results indicate that there has been changes in the resistance due to elevated CO2 because of the evident changes in the proteome. If so, then the results will be similar to those documented by Louw (2007) where up-regulation was due to putative storage proteins, proteins involved in photosynthesis, heat shock proteins and defense proteins. Of course, the pI value and molecular mass of the proteins and the identification of the proteins in these spots, must be determined in future work to specifically identify whether these suggestions are authentic. However, Louw (2007) also reports that the susceptible Betta wheat cultivar, displayed a defence response similar to the HR although it was unable to up-regulate specific defensive proteins against RWA infestation but proteins for broad resistance. Although the changes in the proteins in infested Tugela Dn under elevated CO2 concentration were not accurately identified, the defense mechanism is similar to that portrayed by the susceptible Betta wheat cultivar which shows that the resistance mechanism had been overcome. Because this was a pilot study and preliminary results were obtained due to limited funding and time constraints, suggestions were made on how to further develop the method to obtain statistically significant results.
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Identification of agricultural and industrial pollutants in the Kat River, Eastern Cape and their effect on agricultural products found along the river banks
- Authors: Mutingwende, Nhamo
- Date: 2015
- Subjects: Environmental toxicology , Rivers -- Environmental aspects -- South Africa , Water -- Pollution -- Toxicology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc (Biochemistry)
- Identifier: vital:11291 , http://hdl.handle.net/10353/d1020242 , Environmental toxicology , Rivers -- Environmental aspects -- South Africa , Water -- Pollution -- Toxicology -- South Africa
- Description: There is growing concern that commonly used Pharmaceuticals and Personal Care Products (PPCPs) and pesticides are entering and contaminating drinking water supplies. The use of targeted quantitation of PPCP has been well established but there is an emerging trend to also screen for and identify unexpected environmental pollutants. Chemicals like pesticides hormones and antibiotics are especially of interest because of proven endocrine disrupting effects and a possible development of bacterial resistance. Powerful screening methods are required to detect and quantify the presence of these compounds in our environment. PPCP encompass a wide range of pollutants, including Endocrine Disrupting Compounds (EDC), pesticides, hormones, antibiotics, drugs of abuse, x-ray contrast agents and drinking water disinfection by-products to name a few. In order to properly assess the effects of these compounds on our environment, it is necessary to accurately monitor their presence. The diversity of chemical properties of these compounds makes method development challenging. LC/MS/MS is able to analyse polar, semi-volatile, and thermally labile compounds covering a wide molecular weight range. The new AB SCIEX TripleTOF™5600 LC/MS/MS was used to profile environmental samples for unexpected pollutants, to identify and characterise the chemical composition and structure of the pollutants, and to quantify (based on intensity) the concentration in collected water samples. Liquid Chromatography coupled to tandem Mass Spectrometry (LCMS/ MS) is able to analyse polar, semi-volatile, and thermally labile compounds covering a wide molecular weight range, such as pesticides, antibiotics, drugs of abuse, x-ray contrast agents, drinking water disinfection by-products etc. More recently there is a growing interest from environmental researchers to also screen for and identify non-targeted compounds in environmental samples, including metabolites and degradates, but also completely unexpected pollutants. The new AB SCIEX TripleTOF™5600 LC/MS/MS system is capable of performing highly sensitive and fast MS scanning experiments to search for unknown molecular ions while also performing selective and characteristic MS/MS scanning for further compound identification and, therefore, is the instrument of choice for this challenging task. General unknown screening workflows do not use a target analyte list and compound detection is not based on any prior knowledge, including retention times and information on possible molecular and fragment ions. Therefore, acquired chromatograms are very rich in information and can easily contain thousands of ions from both any compounds present in the sample as well as from the sample matrix itself. Thus, powerful software tools are needed to explore such data to identify the unexpected compound. Water samples were collected both upstream and downstream of two WWTPs (Seymour and Fort Beaufort) and were directly injected on the AB SCIEX TripleTOF™5600 LC/MS/MS after being filtered. 15 sample points along the Kat River, ranging from a point as close to the source as possible to a point just before it joins the Great Fish River were used. The samples collected from the source were used as the control in each of the experiments, the assumption being the closer you get to the source, the less contaminated the water would be for the analysis of pesticides. Points were selected where the Kat River crosses the R67 or on farms where the river was accessible using farm roads. Samples were collected from October 2013 to November 2014.The Peak view software and Analyst software were used in the analysis of PPCPs. The XIC Manager allows you to manage large lists of compounds and perform automatic extracted ion chromatogram (XIC) calculations and review results operations. The results were displayed in the chromatogram pane and the XIC table (see results). The results reported here in this thesis indicate that there is contamination in the Kat River water due to both pesticides and PPCPs. The results also indicate that the food products are also contaminated and hence both the Kat River agricultural produce and its water need to be closely monitored for both pesticide and PPCPs contaminants. Further studies to investigate the quantitative levels of pesticides and PPCPs in the Kat river water to determine if the concentration levels of the detected pesticides are below the reported Maximum Residues Limits will be explored in the future.
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Phytochemical analysis and antibacterial properties of aqueous and ethanol extracts of Brachylaena elliptica (Thurb.) dc. and Brachylaena ilicifolia (Lam.) Phill & Schweick
- Authors: Sagbo, Idowu Jonas
- Date: 2015
- Subjects: Medicinal plants , Traditional medicine , Herbs -- Therapeutic use
- Language: English
- Type: Thesis , Masters , MSc (Biochemistry)
- Identifier: vital:11297 , http://hdl.handle.net/10353/d1021289 , Medicinal plants , Traditional medicine , Herbs -- Therapeutic use
- Description: Resistance of human pathogenic bacterial strains results in selective pressure against known antibiotic. However, plant derived compounds that possess antibacterial potential are currently being investigated for treatment of wound infections in diabetic patients as they are inexpensive and non-toxic. Hence, this dissertation was designed to evaluate two medicinal plants (Brachylaena elliptica and Brachylaena ilicifolia) traditionally used in the treatment of various diseases such as diabetes, and its secondary complications in diabetic patients. The in vitro antioxidant activity of both plants were evaluated using DPPH (1, 1-diphenylhydrazl), ferric reducing power, ABTS (2, 2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid), NO (nitric oxide) and H2O2 (hydrogen peroxide) techniques. The antibacterial test and Minimum inhibitory concentration (MIC) was determined by agar dilution method against 5 bacteria strains (Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pyogene, Proteus vulgaris and Proteus mirabilis) infecting wounds in diabetic patients using amoxicillin and ciprofloxacin as positive control. The phytochemical analyses were assessed using standard published methods. Identification of bioactive components in essential oils of both plants were assessed using GCMS. The aqueous and ethanol extracts of both plants were also evaluated to identify bioactive components using LC-MS. The results of the phytochemical analysis revealed the presence of phenols, tannins, flavanoids, flavanols, proanthocyanidins, saponins and alkaloids in both plants. Both plants indicated strong antioxidant activities which might be due to the presence of bioactive compounds. The aqueous and ethanol leaf extracts of both plants demonstrated appreciable broad spectrum activities against these wound pathogens with MIC ranging between 5 and 0.3 mg/ml. The GC-MS analysis of the essential oils of both plants revealed the presence of monoterpenes, oxygenated sesquiterpenes, phenolics and esters. The LC-MS analysis of the aqueous and ethanol leaf extracts of both plants showed that both plants are rich in alkaloids, terpenes, terpenoids, monoterpernoids, and flavanoids. Conclusively, this study has partially justified the ethnomedicinal use of B. elliptica and B.licifolia leaves for the treatment of various diseases, including diabetes and wound infections caused by bacteria in diabetic patients. These may be attributed to the presence of antioxidant compound such as phenols, flavanoids, saponins, tannins, alkaloids and other phytochemical compounds.
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