Fungi are well-known to produce a tremendous variety of bioactive secondary metabolites which play important roles as pharmaceuticals and agrochemicals. In contrast to random-screening approaches utilized in industry, our research applies ecology-based strategy to the selection of fungi for chemical studies. The research described here involves the chemical investigation of freshwater and fungicolous fungi as producers of novel metabolites with potential practical value. Freshwater fungi, as a distinctive ecological group, have only recently been studied in any depth, and remain underexplored in comparison with other fungal niche groups. Chemical studies of freshwater fungal isolates in our research group have led to the discovery of a variety of new bioactive metabolites, suggesting significant untapped potential among these organisms. Studies in this area described in this thesis led to the discovery of twenty-two new metabolites, many of which display significant antibacterial and/or antifungal activities. Some of these compounds possess novel structural features, such as new ring systems. Mycoparasitic and fungicolous fungi are those that colonize other fungi and could be viewed as potential producers of antifungal agents because of the negative effects they often exert on their hosts. Bioassay-guided fractionation of extracts from cultures of selected mycoparasitic and fungicolous fungal isolates afforded twenty-five new compounds representing diverse structural types. Most of these compounds display biological activity, with some showing antifungal and/or antiinsectan effects. The new secondary metabolites isolated during these studies represent a variety of different biosynthetic classes, including cyclic depsipeptides, nucleosides, polyketides, macrolides, terpenoids, and compounds with mixed biogenetic origin. Their structures were established by analysis of MS and NMR data, chemical degradation or derivatization reactions, and/or X-ray diffraction analysis data. Absolute configuration assignments were achieved by application of different strategies, such as Mosher's method, Marfey's method, or CD spectral analysis. Details of the isolation, structure elucidation, and biological activity of these new compounds are presented in this thesis.

Many years of study have revealed that fungi are excellent sources of novel bioactive secondary metabolites. Some of these secondary metabolites possess therapeutic qualities that improve the quality of life for millions of people. Such metabolites include well known classes such as the penicillins, cephalosporins, and statins, yet many fungi remain underexplored as sources of biologically active metabolites. The research described in this thesis employs an ecology-based approach to targeting fungi for chemical investigation, and describes studies of fungi from two niche groups, fungicolous/mycoparasitic and endophytic fungi, as possible sources of new secondary metabolites with biological activities. In a parallel project, the structures of bioactive compounds isolated from peanut seeds that had been subjected to fungal attack were elucidated in the pursuit of compounds with beneficial bioactivities. Mycoparasitic fungi are those that colonize other fungi by parasitizing the host, often leading to damage to the host fungus. Fungicolous fungi are those that colonize other fungi, but have not been proven to be true mycoparasites. The damage often caused by colonization of host fungi indicates that mycoparasitic and fungicolous fungi can produce antifungal compounds. Chemical investigations of such fungi described in this thesis afforded 37 compounds of various biosynthetic types, seven of which were new. Many of these compounds show antifungal, antimicrobial, and/or cytotoxic effects. Endophytic fungi live asymptomatically within plant tissues and in some cases may provide benefits to the host plant through the production of secondary metabolites. Chemical investigations of corn, wheat, and sorghum endophytes led to the isolation and characterization of 21 compounds, seven of which were new. Many of the endophyte metabolites encountered in this work showed antifungal, antimicrobial, and/or cytotoxic effects. The compounds isolated from peanut seeds were produced in response to fungal attack by an Aspergillus caelatus strain. All of these compounds were stilbene-derived phytoalexins, which are considered to be inducible chemical defenses whose production is elicited or enhanced upon microbial attack. Further studies of these newly identified compounds and their production could lead a a better understanding of how the plant defends itself. Such knowledge could enable researchers to manipulate this mechanism to obtain greater peanut resistance to invasion by pests. Additionally, the health benefits from related stilbene-derived compounds (e.g. resveratrol) from peanuts and other plants have been widely established. Knowledge about the presence of compounds of this type could add to the importance of peanut crop production. The compounds identified in this work were isolated using multiple chromatographic techniques, and the structures were established based on analysis of 1D and 2D NMR data combined with MS, chemical derivatizations, and/or optical measurement data. Absolute configuration assignments were achieved by application of Mosher's Method, CD spectral analysis, and/or chemical derivatizations. Details of the isolation, structure elucidation, and biological activity of these compounds are presented in this thesis.

La lutte biologique par utilisation de micro-organismes a indéniablement un potentiel de développement considérable. Dans un contexte multidisciplinaire et fondamental de physio-phytopathologie moléculaire et répondant à d’éminents enjeux appliqués et attendus par les acteurs de la profession oléicole et les consommateurs, nous nous sommes projetés dans l’étude des propriétés intrinsèques d’un agent de biocontrôle fongique, Trichoderma harzianum (souche Ths97) contre l’agent de la fusariose Fusarium solani (souche Fso14), qui sévit sévèrement sur une culture pérenne majeure pour la Tunisie, l’oléiculture. Deux axes de recherche ont été menés. Dans le premier axe, nous avons démontré que Ths97 est un agent de biocontrôle efficace contre la virulence de F. solani Fso14. Cette capacité s’accompagne d’une accumulation des défenses chez le partenaire végétal, des accumulations qui sont d’autant plus fortes quand l’agent bénéfique est en présence du pathogène (événements de priming). De même, des tests in vitro montrent que Ths97développe des activités mycoparasites envers F. solani Fso14, en émettant des structures d’infection classiques tels des enroulements et accolements d’hyphes, des appressoria et des papilles. Quant au second axe d’étude, nous avons étudié la superfamille des perméases Major Intrinsic Proteins (MIP) dans le genre Trichoderma. Cette famille multigénique n’a jamais été étudiée chez un agent fongique hyperparasite. Sept membres MIP sont présents chez T. harzianum, et se classent en 3 sous-groupes, les AQP, les AQGP et les XIP. La modélisation des structures tridimensionnelles et les fonctions putatives de transport pour l’eau et quelques polyols ont été étudiées. Enfin, leurs patrons transcriptionnels ont été suivis chez Ths97 in planta en situation d’antagonisme et in vitro en situation de parasitisme vis-à-vis de Fso14, et montrent que 4 MIP sont exprimées et régulées différentiellement selon que Ths97 est au contact de Fso14 ou pas. Nos travaux ont donc mis en lumière que Ths97 doit être considéré comme un agent biofongicide et biostimulateur de défenses végétales, puis que les MIP seraient impliqués dans les relations trophiques que met en place T. harzianum avec son environnement. Ces données devraient intégrer le développement de procédés plus efficaces et/ou plus durables pour la protection des cultures d’oliviers en Tunisie ainsi qu’à travers le monde. / Biological disease control through the use of microorganisms has a great potential for future use in integrated pest management. In a multidisciplinary and fundamental context of molecular physio-phytopathology and to provide solutions for the actors in the olive profession and the consumers, we have been studying the activity of a fungal biocontrol agent, Trichoderma harzianum (strain Ths97) against the olive tree pathogen Fusarium solani (strain Fso14), which causes major problems for olive production in Tunisia and elsewhere. The project consists of two parts. In the first part, we have demonstrated that Ths97 is a biocontrol agent effective against the F. solani Fso14 pathogen. Induction of plant defence responses by Ths97 was shown to be partly responsible for the biocontrol effect. In vitro tests further showed that Ths97 develops mycoparasitic activities towards F. solani Fso14, by forming infection structures such as hyphae windings and wedges, appressoria and papillae. In the second part of the study, we investigated the Major Intrinsic Proteins (MIP) superfamily in the Trichoderma genus. This multigenic family has never been investigated in a hyperparasitic fungal species. Seven MIP members are present in T. harzianum, and are classified into 3 subgroups: AQP, AQGP and XIP. Their three-dimensional structures and their putative involvement in transport of water and certain polyols have been examined. Finally, their transcription profiles were monitored in Ths97 in planta in antagonistic situations and in vitro in a parasitic situation with Fso14 and show that 4 MIP are expressed and regulated differentially during the interaction. Our work has shown that Ths97 must be considered as a biological control agent and biostimulator of plant defences, and that MIPs are involved in the trophic relationships between T. harzianum and the environment. These data contributes to the further development of T. harzianum as an efficient biocontrol agent for sustainable protection of olive trees in Tunisia and around the world.

The thesis is focused on monitoring of natural occurrence of mycoparasitic fungi in arable soils. Study was aimed to isolate those fungi from selected plots with conventional and organic farming systems of the region of South Bohemia. Four isolated method were used for isolation of mycoparasitic fungi from soil.Among all, species of genus of Trichoderma, Trichoderma virens, Clonostachys rosea f. catenulata and Lecanicillium muscarium were the most frequently present and isolated species.The radial growth of strains and their production characteristic was evaluated. The efficacy of Trichoderma strains against phytopathogenic fungi (S. sclerotiorum, Rhizoctonia solani, Botrytis cinerea a Fusarium solani) was evaluated.

No description available.

This M. Sc. thesis is based on using of mycoparasitic fungi Trichoderma virens, Clonostachys rosea f. catenulata in biological control against phytopathogenic fungi Sclerotinia sclerotiorum, Rhizoctonia solani, Botrytis cinerea and Fusarium solani. The efficacy of mycoparasitic fungi against pathogens was evaluated in dual cultural tests. The strains of T. virens and C. rosea f. catenulata isolated from soils in the Czech Republic were tested in the experiment. Reference strain was GL 21 fungus T. virens reisolated from commercially available bio-preparation SoilGard and strain C. rosea f. catenulata reisolated from Prestop Mix. All the strains were tested for biological and production properties. All strains are able to colonize the substrate and to suppress the growth and development of pathogens. Strain GL 21 of T. virens was used for seed coating of variety Scirocco in combination with products Guar gum and Carboxymethyl cellulose, which served as a carrier for stick on conidia. After 3 days, the effect of fungus T. virens was evaluated on energy of germination, development of roots of grain. The grain health was determined after 7 days. The fungus T. virens has a positive effect on the grains germination and grain health. During the vegetation the influence of seed coating by T. virens was observed on growth and development of spring wheat. The parameters such as number of plants per m2, tiller numbers, plants health, stand height, number of grains in the spike and thousand grain weight (TGW) were evaluated. During the vegetation the fungus T. virens has positive effect on the plant height.