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).

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

No description available.

Background. Fungal endophytes inhabit symptomless, living tissues of all major plant lineages to form one of earth's most prevalent groups of symbionts. Many reproduce from senesced and/or decomposing leaves and can produce extracellular leaf degrading enzymes, blurring the line between symbiotrophy and saprotrophy. To better understand the endophyte saprotroph continuum we compared fungal communities and functional traits of focal strains isolated from living leaves to those isolated from leaves after senescence and decomposition, with a focus on foliage of woody plants in five biogeographic provinces ranging from tundra to subtropical scrub forest. Methods. We cultured fungi from the interior of surface-sterilized leaves that were living at the time. of sampling (i.e., dophytes), leaves that were dead and were retained in plant canopies (dead leaf fungi,eDn LF), and fallen. leaves (leaf litter.fungi,LLF) from 3-4 species of woody plants in each of five sites in. North America. Our sampling encompassed 18 plant species. representing. two families of Pinophyta.and five families of Angiospermae. Diversity and composition of fungal communities within and among leaf life stages, hosts, and sites were compared using ITS-partial L SU rDNA data. We evaluated substrate use and enzyme activity by a subset of fungi isolated'onlyfrom living tissues vs. fungi isolated only from non-living leaves. Results Across the diverse biomes and plant taxa surveyed here, culturable fungi living leays were isolated less frequently and were less diverse than those isolated from non-living leaves. Fungal communities in living leaves also differed detectably in composition from communities in dead leaves and leaf litter within focal sites and host taxa, regardless of differential weighting of rare and abundant fungi. All focal isolates grew on cellulose, lignin, and pectin as sole carbon sources, but none displayed igninolytic or pectinolytic activity in vitro. Cellulolytic activity differed among fungal classes. Within Dothideomycetes, activity differed significantly between fungi from living vs. non-living leaves, but such differences were not observed in Sordariomycetes. Discussion. Although some fungi with endophytic life stages clearly persist for periods of time in leaves after senescence and incorporation into leaf litter, our sampling across diverse biomes and host lineages detected consistent differences between fungal assemblages in living vs. non-living leaves, reflecting incursion by fungi from the leaf exterior after leaf death and as leaves begin to decompose. However, fungi found only in living leaves do not differ consistently in cellulolytic activity from those fungi detected thus far only in dead leaves. Future analyses should consider Basidiornycota in addition to the Ascomycota fungi evaluated here, and should explore more dimensions of functional traits and persistence to further define the endophytism-to-saprotrophy continuum.

Orientadora: Dulce Helena Siqueira Silva / Banca: Cintia Duarte de Freitas Milagre / Banca: Mariana Helena Chaves / Resumo: Sabe-se que os fungos exercem importantes papéis no cotidiano, sendo utilizados na produção de alimentos fermentados e de enzimas de interesse industrial, em processos de biodegradação e tratamento biológico de efluentes, além de auxiliar na agricultura como parte do corpo de decompositores, e ainda na defesa e crescimento de plantas em que vivem em simbiose. Adicionalmente, nos últimos anos, as pesquisas com fungos e outros micro-organismos têm-se intensificado pelo surgimento de evidências crescentes de seu potencial como fonte de substâncias bioativas para o desenvolvimento de agentes terapêuticos, como as penicilinas e cefalosporinas - antibióticos, a mevastatina e lovastatina - redutores de colesterol, ciclosporina e rapamicina-imunossupressores, entre outros. Muitos fungos endofíticos possuem potencial farmacológico, demonstrando atividades como citotóxica, antibacteriana, anticolinesterásica, antifúngica, antiplasmódica, entre outras. Além de indicarem ser fonte de uma grande variedade de novos metabólitos secundários, decorrente de sua quimiodiversidade marcante. Este contexto levou à investigação de uma linhagem fúngica isolada da alga marinha Asparagopsis taxiformis (Delile) Trevisan, identificada como Microascus intricatus. O cultivo desta linhagem em meio PDB por 28 dias, 65 frascos de Erlenmeyer forneceu o extrato AT-07, que foi submetido a partição com acetato de etila. As frações AT-07 F3, AT-07 F4 e AT-07 F6 foram submetidas a procedimentos cromatográficos e l... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Fungi play important roles in our daily life as in the production of fermented food and enzymes for industrial applications, biodegradation processes and biological treatment of effluents, in addition to its roles in agriculture, enhancing decomposition, and defense and growth of plants living in symbiosis.Research involving fungi and other microorganisms has been intensified in the last decades owing to growing evidence of their potential as important sources of novel bioactive compounds for the development of therapeutic agents as penicillins, cephalosporins (antibiotics), mevastatin and lovastatin (cholesterol lowering agents), cyclosporine and rapamycin (immunosuppressors), among others.Several endophytic fungal strains exhibit pharmacological potential as cytotoxic, antibacterial, anticholinesterase antifungal, antiplasmodial activities, which has been markedly associated to the huge chemodiversity of their secondary metabolites.Such context prompted us to investigate one fungal strain isolated from marine red alga Asparagopsis taxiformis (Delile) Trevisan, which has been identified as Microascus intricatus.Cultivation of the fungal strain in PDB media for 28 days, Erlenmeyr flasks yielded extract AT-07 partition with etoac extract which was submitted to chromatographic procedures and led to the isolation of natural products belonging to diketopiperazines classes and one isoflavone.The isolated compounds were identified as cyclo-(Pro-Tir), cyclo-(ProPhe), cyclo-(Phe-Phe)... (Complete abstract click electronic access below) / Mestre

Thesis (Ph.D.) -- Flinders University, Dept. of Medical Biotechnology. / Typescript (bound). Includes bibliographical references (leaves 256 - 283). Also available online.

Thesis (M.Sc.)--York University, 2006. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 76-81). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19648

Thesis (M.S.)--University of Tennessee, Knoxville, 2004. / Title from title page screen (viewed Oct. 04, 2004). Thesis advisor: F. Neal Schrick. Document formatted into pages (xiii,105 p. : ill.). Vita. Includes bibliographical references (p. 86-104).

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 95 p. : ill. Includes abstract. Includes bibliographical references (p. 68-76).