Thesis (M.S.)--Mississippi State University. Department of Entomology and Plant Pathology. / Title from title screen. Includes bibliographical references.

A series of pot trials were undertaken to test the growth of indigenous grasses (Themeda triandra and Cynodon dactylon) on mine capping soil, treated with various soil ameliorants. The capping soils were obtained from open cast coal mines (Optimum Mine and Syferfontein Mine) in the Mpumalanga Highveld, south of Witbank. However, because mine soil was not available at the commencement of the project, the initial pot trial used soil from the Umlazi Landfill in Durban. The trials were the Umlazi Landfill Trial, Microbe Trial, Legume Trial and Fly Ash Trial. For the Umlazi Landfill Trial, landfill top and subsoil was used along with fertilizer, sewage sludge, K-humate, lime and microbes. The soil ameliorant treatments for the Microbe trial were Trichoderma harzianum (Eco'T), Bacillus subtilis Strain 69 (B69) and Bacillus subtilis Strain 77 (B77), for the Legume Trial, Medicago sativa, phosphorus and/or potassium were applied. For the Fly Ash Trial, lime and fly ash were introduced. From the Landfill trial it was shown that fertilizer and sewage sludge significantly increased the above ground, below ground and total biomass of T. triandra, further, there were no significant treatment differences between fertilizer and sludge. The lime treatment for this trial, surprisingly, significantly reduced below ground biomass but the application of microbes (B69 and BcoT) alleviated this negative effect. However, in the Microbe Trial the microbes (BcoT, B69 and B77) had a negative or no effect on the biomass of T. triandra and C. dactylon. In the Legume Trial it was shown that the above ground biomass of T. triandra was significantly reduced when grown with M. sativa. The Fly Ash Trial revealed that the lime and fly ash treatments had no effect on the biomass of M. sativa and T. triandra, and they did not maintain a reduction in soil acidity. The results therefore indicated that either organic fertilizer or sewage sludge could be used to significantly improve the growth of T. triandra. It was also suggested that lime not be applied to soils with an acid saturation of approximately 1%, as this could retard plant growth. The application of microbes and the growth of a legume with grass, although both have been recorded to have beneficial effects in aiding plant growth, in the short-term however, the application of T. harzianum, B. subtilis Strain 69 and 77 applied to the soil while growing T.triandra and C. dactylon and the growth of M. sativa with T. triandra is not recommended. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Fundamental processes underpinning the biotransformation of coal by fungal biocatalysts have been intensively investigated, however, limited large-scale industrial applications using such systems have been reported. The un-anticipated sporadic growth of Cynodon dactylon on the surface of un-rehabilitated discard coal dumps has been noted and this was found to be coupled with the breakdown of coal into a humic soil-like material in the top 1.5 metres of the dumps. Extensive fungal growth was observed to be associated with the Cynodon dactylon root system and examination of plant roots indicated the presence of mycorrhizal fungi. Analysis of the Cynodon dactylon plant roots around which coal biotransformation was occurring confirmed the presence of arbuscular mycorrhizal colonisation with the species Glomus clarum, Paraglomus occultum, Gigaspora gigantea and Glomus mosseae identified to be associated with the plants. Further molecular characterisation of non-mycorrhizal rhizospheric fungi showed the presence of fungal species with coal-degrading capabilities that most likely played a role in the coal biotransformation observed. The discard coal dump environment was simulated in pot and column studies and coal biotransformation was reproduced, with this process enhanced by the addition of mycorrhizal and non-mycorrhizal rhizospheric fungal inocula to the environment. Mycorrhizal and non-mycorrhizal species in the inoculum were re-isolated from the simulated environment fulfilling a number of Koch’s postulates and indicating a causal role in the biotransformation of coal. An inversion of conventional mycorrhizal colonisation was demonstrated in this system with reduction in extraradicular presence and an increase in intracellular colonisation compared to soil controls. A descriptive model was formulated suggesting a two-part fungal system involving organic carbon and nutrient exchange between the plant, mycorrhizal fungi and non-mycorrhizal coal-degrading rhizospheric fungi ultimately resulting in the biotransformation of coal. The biotransformation observed was comparable to reports of “rock-eating fungi”. Results suggest that the biological degradation of coal in situ with the production of a soil-like substrate could provide a feasible method of discard coal dump rehabilitation as well as provide a humic-rich substrate that can be utilised in further industrial applications.

Anopheles gambiae sensu lato mosquitoes are among the dominant malaria vectors in sub-Saharan Africa. However, not much is known about the oviposition behaviour of these species necessary for the development of malaria vector control strategies. With the aim of investigating cues associated with selected oviposition sites, artificial oviposition sites- ponds (soil mixed with water) were set-up in an open field at Mbita, Western Kenya in 2012 and 2013. Ponds were allowed to be colonized by wild An. gambiae s.l.. The numbers of Anopheles early instar larvae were counted and used as a proxy for oviposition preference. Water samples were then analysed for physicochemical, bacterial and chemical profiles. The bacterial profiles were analysed using denaturing gradient gel electrophoresis (DGGE) and the chemical profiles with gas chromatography-mass spectrometry (GC-MS). The detection of possible oviposition cues from oviposition substrates requires sensitive analytical methods. Volatiles detection was improved seven times. The detection of bacteria deoxyribonucleic acid (DNA) bands with DGGE was also improved to a minimum DNA concentration of 50 ng/µl. Results showed that ponds were colonized differently. Fresh ponds were preferred over slightly older ponds. Bacterial analysis revealed a low number of bacteria colony forming units (CFU) in preferred ponds. Some volatiles, including: 6,10-dimethyl-5,9-undecadien-2-one (geranylacetone) and 4-ethylbenzaldehyde, were associated with the oviposition preferred pond. In addition, low pH and high turbidity were associated with the ponds selected for oviposition. Finally, fungi isolated from the rhizomes of nut grass yielded a promising array of volatiles of which one is known to attract oviposition site seeking malaria mosquitoes. This finding opens the door for a cost effective and environmental friendly method of using fungi in an “attract and kill” strategy targeting malaria vectors. / Myggor i Anopheles gambiae sensu lato komplexet tillhör de myggor som är bäst på att sprida malaria parasiter i afrika söder om Sahara. Kunskapen om de här myggornas äggläggningsbeteende är begränsad. Den här kunskapen behövs för att kunna utveckla nya och förbättra tillgängliga malaria vektor kontroll metoder. Nya metoder som kan komplettera de som används idag (insecticides treated nets (ITNs) och indoor residual spraying (IRS)) behövs eftersom de metoderna har problem med resistensutveckling. Två studier utfördes på icipe fältstation i Mbita västra Kenya under 2012 och 2013 med målet att identifiera faktorer som påverkar myggornas äggläggningsbeteende. Baljor fyllda med en blandning av jord och vatten (äggläggningssubstrat) användes för att tillverka artificiella äggläggningsplatser som liknar de vattenpölar som de här myggarterna gärna lägger ägg i. Baljorna koloniserades av vilda myggor och antalet mygglarver som detekterades i baljorna jämfördes och användes som en proxy för äggläggningspreferens. Fysikaliska och kemiska parametrar mättes på jordvattenblandningarna i baljorna och prover togs för att analysera bakteriepopulationer med hjälp av denaturing gradient gel electrophoresis (DGGE) och flyktiga ämnen med hjälp av gas-kromatografi kopplat till mass-spektrometri (GC-MS). För att kunna detektera de låga halter av flyktiga ämnen och bakterier som fanns i de här proverna krävdes det känsliga metoder. Antalet flyktiga ämnen som kunde detekteras ökades sju gånger genom att tillsätta NaCl till vattenproverna innan doften insamlades och termisk desorption användes istället för lösningsmedels desorption. För att förbättra detektionsgränsen för bakterier amplifierades bakterie-DNA i två PCR reaktioner som sedan mixades och koncentrerades. Resultaten från fältstudierna med baljorna visade att de koloniserades olika av Anopheles myggorna. Baljor med nyblandat substrat innehöll dubbelt så många mygglarver som baljor med jord-vattensubstrat som åldrats under en längre tid. Lägre mängd bakterier, lägre pH och högre grumlighet var gemensamt för de baljor som myggorna föredrog. De flyktiga ämnen som detekterades i de olika baljor varierade mellan olika försök och inget ämne fanns med i alla upprepningar av ett försök. Trots det detekterades några ämnen oftare i de baljor som myggorna föredrog att lägga ägg jämfört med de med en mindre mängd mygglarver. De inkluderar geranylacetone och 4-ethylbenzaldehyde. Svampar isolerades från rotstockar av gräs som fanns i den jord som användes för att göra äggläggningssubstraten i fältstudierna. De flyktiga ämnen som avgavs från svampkulturerna analyserades. Bland annat så identifierades ett ämne som fungerar som en äggläggningsattrahent för An. gambiae s.l. myggor.Resultaten från den här avhandlingen kommer att kunna användas för att utveckla miljövänliga ”attract and kill” metoder för att kontrollera malaria myggor. / <p>QC 20160211</p>