published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

Thesis (M.S.)--University of Tennessee, Knoxville, 2008. / Title from title page screen (viewed on Mar. 20, 2009). Thesis advisor: John C. Waller. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 130-141). Also available via World Wide Web.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 100-117).

Thesis (PhD.(Plant Pathology))--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Fungal endophytes live inside plants without causing apparent symptoms of infection. All plant species surveyed thus far, including liverworts, mosses, seedless vascular plants, conifers, and angiosperms, harbor one or more endophytic fungi. Fungal endophytes can be divided into four groups including class 1, class 2, class 3 and class 4 endophytic fungi according to host range, colonization pattern, transmission, and ecological function. Class 2 fungal endophytes benefit their host by increasing environmental stress tolerance (i.e. water, temperature, salt) in a habitat-specific manner. In my study, class 2 fungal endophytes were studied from weedy plants growing in an environmentally stressed area: mine tailings from the Athabasca oil sands. This area is a vast hydrocarbon reserve in western Canada that supplies 10% of Canadian oil needs. Hydrocarbons are extracted from tar sands with hot water, alkali, and solvents. The tailing sands can later be remediated (by adding organic material and fertilizer) to establish new plant communities. Prior to remediation, tailing sands have extremely low content of organic carbon and available minerals, and are hydrophobic compared to unimpacted and remediated soils. Nevertheless, <i>Taraxacum</i> (dandelion) and <i>Sonchus</i> (sow-thistle) can colonize extracted tailing sands even prior to remediation. Preliminary results show that pioneer plants have similar fungal abundance as plants of unextracted treatments. Fungal endophytes were isolated from surface sterilized <i>Taraxacum</i> and <i>Sonchus</i> that had been growing upon unimpacted, remediated and extracted soil. Fungi isolated in this way included <i>Alternaria, Tricoderma, Fusarium</i> and an unidentified <i>Perithecial Ascomycote</i>. These endophytic fungi were used to inoculate tomato plants in a greenhouse trial to determine whether they confer stress tolerance to host plants, especially for drought and low mineral nutrition. Before exposing the tomato plants to environmental stresses, the specific endophytic fungal strains applied were successfully recovered from tomato plants originally inoculated with the same endophytic fungi. Although the other endophytic fungi turned out to be harmful to the tomato plants in the test, a <i>Trichoderma spp.</i> strain isolated from samples of extracted treatment appears to confer tolerance of tailing sands to the tomato plants. This <i>Trichoderma spp.</i> strain which we can call <i>TSTh20-1</i> was molecularly identified as <i>Trichoderma harzianum</i>. Despite an identification to species, all strains of <i>T. harzianum</i> are not necessarily identical regarding strain-specific attributes. Using similar techniques described here, it is possible to isolate and potentially use beneficial class 2 endophytic fungal strains for the remediation process in the Athabasca oil sands or to assist plant growth in other high stress environments.

Fungal endophytes live inside plants without causing apparent symptoms of infection. All plant species surveyed thus far, including liverworts, mosses, seedless vascular plants, conifers, and angiosperms, harbor one or more endophytic fungi. Fungal endophytes can be divided into four groups including class 1, class 2, class 3 and class 4 endophytic fungi according to host range, colonization pattern, transmission, and ecological function. Class 2 fungal endophytes benefit their host by increasing environmental stress tolerance (i.e. water, temperature, salt) in a habitat-specific manner. In my study, class 2 fungal endophytes were studied from weedy plants growing in an environmentally stressed area: mine tailings from the Athabasca oil sands. This area is a vast hydrocarbon reserve in western Canada that supplies 10% of Canadian oil needs. Hydrocarbons are extracted from tar sands with hot water, alkali, and solvents. The tailing sands can later be remediated (by adding organic material and fertilizer) to establish new plant communities. Prior to remediation, tailing sands have extremely low content of organic carbon and available minerals, and are hydrophobic compared to unimpacted and remediated soils. Nevertheless, <i>Taraxacum</i> (dandelion) and <i>Sonchus</i> (sow-thistle) can colonize extracted tailing sands even prior to remediation. Preliminary results show that pioneer plants have similar fungal abundance as plants of unextracted treatments. Fungal endophytes were isolated from surface sterilized <i>Taraxacum</i> and <i>Sonchus</i> that had been growing upon unimpacted, remediated and extracted soil. Fungi isolated in this way included <i>Alternaria, Tricoderma, Fusarium</i> and an unidentified <i>Perithecial Ascomycote</i>. These endophytic fungi were used to inoculate tomato plants in a greenhouse trial to determine whether they confer stress tolerance to host plants, especially for drought and low mineral nutrition. Before exposing the tomato plants to environmental stresses, the specific endophytic fungal strains applied were successfully recovered from tomato plants originally inoculated with the same endophytic fungi. Although the other endophytic fungi turned out to be harmful to the tomato plants in the test, a <i>Trichoderma spp.</i> strain isolated from samples of extracted treatment appears to confer tolerance of tailing sands to the tomato plants. This <i>Trichoderma spp.</i> strain which we can call <i>TSTh20-1</i> was molecularly identified as <i>Trichoderma harzianum</i>. Despite an identification to species, all strains of <i>T. harzianum</i> are not necessarily identical regarding strain-specific attributes. Using similar techniques described here, it is possible to isolate and potentially use beneficial class 2 endophytic fungal strains for the remediation process in the Athabasca oil sands or to assist plant growth in other high stress environments.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains viii, 62 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical reference.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 179-212) Also available in print.