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.

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (leaves 76-89).

Thesis (Ph. D.)--University of Kentucky, 2004. / Title from document title page (viewed Sept. 14, 2004). Document formatted into pages; contains ix, 97 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 86-96).

Orientador: Ângela Regina Araújo / Banca: Dulce Helena Siqueira Silva / Banca: Lourdes Campaner dos Santos / Banca: Hosana Maria Debonsi / Banca: Dionéia Camilo Rodrigues de Oliveira / Resumo: Este trabalho descreve a triagem de 21 fungos endofíticos associados a espécies vegetais de Cerrado e Mata Atlântica. Os extratos brutos fornecidos por estes fungos foram avaliados quimicamente (CLAE e RMN1H) e submetidos a bioensaios para avaliação da potencialidade antifúngica, antioxidante e anticolinesterásica, onde se mostraram promissores. Após esta triagem, os fungos Xylaria sp. E Colletotrichum crassipes, associados a Casearia sylvestris, foram selecionados para o estudo químico/biológico. Estes fungos foram cultivados nos meios líquido (MDB) e sólido (milho) para obtenção dos extratos brutos. O extrato bruto de Xylaria sp. em milho foi submetido a fracionamento cromatográfico e levou ao isolamento da griseofulvina, 7-desclorogriseofulvina e citocalasina B, enquanto que o extrato obtido do meio líquido conduziu ao isolamento da citocalasina D, citocalasina C e 5-carbóxi-6-hidroxi-3-metil-3,4- diidroisocumarina. Após fracionamento do extrato bruto do endófito C. crassipes no meio líquido MDB foram isoladas 8 substâncias da classe de dicetopiperazinas, N-(2-feniletil)acetamida, tirosol e as substâncias inéditas 1-hidroxi-1-feniletil-tirosol e (6-metil-3- (feniletóxi)-1,4-dioxan-2-il)metanol. Algumas substâncias puras foram submetidas à bioensaios e apresentaram potencial bioatividade frente aos fungos fitopatogênicos Cladosporium cladosporioides e C. sphaerospermum e nos ensaios antioxidante e anticolinesterásico. As citocalasinas D e B isoladas durante este trabalho e outras 5 citocalasinas isoladas anteriormente foram submetidas à avaliação da citotoxicidade utilizando linhagens de células de adenocarcinoma murino e se mostraram muito ativas. Os fungos endofíticos Xylaria sp. e C. crassipes foram utilizados em biotransformação do substrato 4-etilciclohexanona. Este experimento foi realizado através do cultivo ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work describes the screening of 21 endophytic fungi from plant species from Cerrado and Atlantic Forest. The crude extracts produced by these fungi after fermentation in potato dextrose broth (PDB) were evaluated by HPLC, 1HNMR and potential biological activities: antifungal, antioxidant and anticholinesterasic. After screening, the extracts of Xylaria sp. and Colletotrichum crassipes, isolated from Casearia sylvestris, were selected, based on the chemical/biological results. These endophytic fungi were cultivated in PDB and corn for crude extract preparation. The crude corn extract of Xylaria sp. led to isolation of griseofulvin, 7- dechlorogriseofulvin and cytochalasin B while the crude PDB extract led to isolation of cytochalasin C, cytochalasin D and 5-carboxy-6- hidroxy-3-methyl-3,4-dihydroisocoumarin. The crude PDB extract of Colletotrichum crassipes led to isolation of eight diketopiperazines, N-(2-phenylethyl)acetamide, tyrosol, 1-hidroxy-1- phenylethyl-tyrosol and (6-methyl-3-(phenethyloxy)-1,4-dioxan-2- yl)methanol. The some of them pure compounds showed potential antifungal activity against Cladosporium cladosporioides and C. sphaeropermum, antioxidant and anticholinesterasic activities. The Cytochalasins D and B, isolated in this work, and other five cytochalasins produced by Xylaria sp.1 showed potential activity for cytotoxic activity against adenocarcinomatous murine cells. The fungi Xylaria sp. and C. crassipes were evaluated as biocatalysts for biotransformation of 4-ethylcyclohexanone. Four biotransformation products were isolated. Their structures were established by spectroscopic methods, including the application of bidimensional NMR techniques and comparison with published data. / Doutor

>Magister Scientiae - MSc / The term endophyte is used to define all microorganisms that, during a part of their life cycle, colonize the internal tissues of a plant host. Many endophytes have been found to promote plant growth by acting either as biocontrol agents, biofertilizers or phytohormone producers. This study aimed to characterise the endophytic microbial community diversity associated with sorghum farmed in South Africa. Members of any common endophytic bacterial species identified during the study might in future studies be developed to improve sorghum production. Sorghum tissues (roots, shoots, stems) were sampled in three South African provinces (Free State, Limpopo and North West), each site being characterised by the use of different agricultural practices. Denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) analyses were used to characterise the endophytic bacterial communities. The analysis clearly demonstrated that the endophytic bacterial community structure in the three sorghum tissue types differed, suggesting that endophyte colonization is tissue-specific. The endophytic bacterial community structure is quite similar in each tissue when comparing the populations present in the sampling sites. In the sorghum endophytic microbial communities, common bacterial species were identified using molecular tools: The cyanobacterium Synechococcus and Staphylococcus saprophyticus were identified in the root samples. Pantoea sp., Erwinia sp., Enterobacter sp. and Klebsiella sp. were found in all shoot samples. Nocardia fluminea, Bacillus cereus and Microbacterium sp. were isolated as common shoot endophytic bacteria. This study defines, for the first time, the endophytic bacterial species associated with South African sorghum plants. These common endophytic bacterial species can be used to enhance the yield of sorghum crops.

Radopholus similis is one of the key pests of banana in the East African Highlands and in the world. Although control of this pest has mainly relied on the use of clean planting material, re-infestation of plants in the field remains a critical concern. Alternative management options such as the use of fungal endophytes may be used to provide protection and extend plant life. In this study, a total of 35 endophytic Fusarium isolates were screened for the production of secondary metabolites antagonistic to R. similis in culture. Undiluted and diluted culture filtrates were tested against motile stages of R. similis and eggs. Tests were conducted using culture filtrates of the fungal isolates grown in banana corm broth. All isolates tested demonstrated some level of in vitro antagonistic activity on the mobility of R. similis mixed stages (males, females and juveniles). The percentage of immobilized nematodes increased with increase in the length of exposure time to culture filtrates. After 24 hrs exposure, up to 100% of nematodes were immobilized compared to 26.5% in control treatments. Mortality of mixed stages of R. similis exposed to culture filtrates for 24 hrs, followed by rinsing with sterile distilled water, demonstrated that the effects of culture filtrate treatment were irreversible, as nematodes did not recover and were considered dead. Nematode mortality rates after 24-hr exposure periods ranged from 76.4% to 100.0%. The effects of culture filtrates on R. similis motile stages increased with increasing culture filtrate concentration. Culture filtrates also demonstrated inhibitory effects on hatching of R. similis eggs. Radopholus similis males were more sensitive to culture filtrate treatment than females. The results obtained demonstrate the potential for using endophytic Fusarium isolates as biological control agents against R. similis and/or toxic derivatives as potential nematicides against the nematode. / Thesis (PhD (Plant Pathology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

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