No description available.

Economic losses caused by the two spotted spider mite (Tetranychus urticae Koch) in the agricultural industry prompted the initiation of this project to evaluate the potential of native and exotic Beauveria bassiana isolates as biocontrol agents against this pest. Before the selection of a potential mycopesticide for use at a commercial scale, several crucial criteria must be taken into consideration. The application of some of these criteria have been the focus of this study and include: production of virulent B. bassiana inoculum, an evaluation of the virulence of the fungus against T. urticae, monitoring of the fungal infection cycle in T. urticae and establishing a phylogenetic evaluation of B. bassiana isolates using rDNA sequence analysis. A two-stage in vitro diphasic fermentation process produced B. bassiana inoculum. In the first submerged phase the impact of nutrient treatments (carbon and nitrogen) at different concentrations (3% and 4%) in a 1:1 ratio was investigated for mycelium dry mass production and spore yield. The 4% nutrient concentration yielded a higher mycelium dry mass yield compared to the 3% and was therefore used in the second semi-solid phase to stimulate aerial conidia formation in response to low nutrient stress. The fungal structures produced during the first phase of the diphasic fermentation process were submerged conidia recognized as small, spherical structures with a smooth form. In comparison, inoculum of the second semi-solid phase produced aerial conidia with small, spherical, rough surfaces and a brittle appearance assumed to be related to nutrient deprivation. Nutritional parameters exploited in this study favoured conidia production for use as a potential mycopesticide. An in vitro bioassay compared the infectivity of exotic and native isolates of B. bassiana against T. urticae adults. All the isolates were pathogenic with mite mortality increasing over time. Differences in the virulence of the B. bassiana isolates were demonstrated suggesting host-specificity. With respect to the native isolates B. bassiana (PPRI 04305) was more virulent than the B. bassiana sensu latu isolates (PPRI 04304 and PPRI 04306). The differences in the virulence of the native isolates are reflections of genetic differences demonstrated in the phylogenetic analyses in this study. The results of the preliminary bioassay study suggest that B. bassiana has the potential as a biocontrol agent of T. urticae. Microscopy was used to morphologically visualise the post infection cycle of a native B. bassiana isolate (PPRI 04305) in the two-spotted spider mite. The infection cycle observed in the current study is in agreement with those described in a number of agricultural pests. However, aspects not observed before with T. urticae infection included limited hyphal growth on the cuticle surface before penetration, per os mode of entry, cuticular melanization, lateral hyphal development under the cuticle and aerial hyphal emergence through the setal annulum on the dorsal surface of the cadaver. These observations will stimulate further research in the development of B. bassiana as a mycoacaricide. rDNA analysis of the ITS1-5.8S-ITS2 regions of different Beauveria species was assessed for strain genotyping and population studies. Fitch parsimony and neighbour joining analyses displayed species differentiation and confirmed that B. bassiana was not a monophyletic group but a species complex. Distinct clades in the phylogenetic analyses in the current study were matched to four species of Beauveria: B. bassiana, B. cf. bassiana, Beauveria brongniartii and Beauveria caledonica species. Two South African isolates PPRI 04304 and PPRI 04306 morphologically assigned to B. bassiana, are assumed to be either B. caledonica or a close relative of B. caledonica based on the rDNA analysis. However, due to the lack of confirmation of the change of species identification of these native isolates, they are regarded as B. bassiana sensu latu. Results from this study demonstrated the importance of rDNA analysis in biocontrol studies for population studies and species differentiation. The material in this dissertation highlighted some important characteristics relevant for the biocontrol of T. urticae by B. bassiana. Aerial conidia produced by the cost-effective diphasic fermentation process were virulent against T. urticae and demonstrated high percentage mortalities. B. bassiana was shown to be a generalist pathogen with strain-dependent differences in nutrient preferences and virulence against the mite. Differences in the infectivity of the native isolates B. bassiana (PPRI 04305) and B. bassiana sensu latu (PPRI 04304 and PPRI 04306) were reflections of the genotypic separation of the isolates demonstrated by rDNA analysis. The results obtained from this research project are promising for the ongoing research and development of Beauveria isolates as efficient mycoacaricides against T. urticae for the South African agricultural market.

Thesis (M.S.) in Entomology--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 46-52).

No description available.

Doctor of Philosophy / Department of Biology / Kristin Michel / Malaria remains a major human vector-borne disease, greatly contributing to global human morbidity and mortality. Control of mosquito vectors that transmit malaria continues to be dependent on the widespread application of chemical insecticides through indoor residual spraying and insecticide treated bed nets. However, resistance to these insecticides is spreading within many mosquito populations, adding an ever-increasing urgency to the development of alternative vector control measures. The mosquito immune system is a potential novel target for such alternative measures, as the immune response initiated in these insects during infection with vector-borne disease agents is a key determinant of vector competence and, thus, contributes to a species’ vectorial capacity. These immune responses, additionally, interact with and respond to parasitic or symbiotic biocontrol agents employed to kill or manipulate infection outcome with vector-borne disease agents. Entomopathogenic fungi, including Beauveria bassiana, have been considered as an alternative vector control measure, functioning as biopesticides. The Toll pathway is a key antifungal immune pathway in insects that impacts an insect’s ability to survive fungal infections. A better understanding of Toll signaling immune function and evolution in anophelines, both vector and nonvector, can thus help to improve future biocontrol methods of important vector mosquitoes like Anopheles gambiae. In this dissertation, I report the use of B. bassiana strain I93-825 in An. gambiae to analyze the impact of Toll pathway modulation on mosquito survival. Mosquito survivorship was strongly affected by B. bassiana exposure dose by several measured parameters including median survival, longevity, and hazard. Modulation of Toll signaling, by way of knockdown by RNA interference, revealed a dose-dependent trade-off between immune activation state and survivorship in An. gambiae. To better determine the full Toll immune signaling repertoire in mosquitoes, I annotated and describe the evolutionary history of intracellular Toll pathway members and Toll-like receptors (TLRs) within 21 mosquito genomes. The intracellular signaling pathway is conserved with 1:1 orthology, and evolutionary rates across different intracellular pathway members vary widely as compared to the conserved protein core of these mosquito species. In contrast, TLRs evolved largely by duplication events within certain anopheline lineages, most dramatically in the An. gambiae complex, where six TOLL1/5 paralogs likely possess different ligand binding specificities. Thus, these TLRs should be prioritized for experimental analyses of TLR immune function in An. gambiae. Taken together, the work in this dissertation identifies Toll pathway modulation as a potential resistance mechanism that could impact malaria biocontrol strategies and provides a foundation for future detailed studies of Toll pathway function in important mosquito vector species.

Submitted by FERNANDA DA SILVA VON PORSTER (fdsvporster@univates.br) on 2017-06-22T18:56:45Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) 2016LiseteAparecidaSilvaKlein.pdf: 1141562 bytes, checksum: 5b220c02ace2690bb07ba88bb7aeebe6 (MD5) / Approved for entry into archive by Ana Paula Lisboa Monteiro (monteiro@univates.br) on 2017-06-26T18:50:11Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) 2016LiseteAparecidaSilvaKlein.pdf: 1141562 bytes, checksum: 5b220c02ace2690bb07ba88bb7aeebe6 (MD5) / Made available in DSpace on 2017-06-26T18:50:11Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) 2016LiseteAparecidaSilvaKlein.pdf: 1141562 bytes, checksum: 5b220c02ace2690bb07ba88bb7aeebe6 (MD5) Previous issue date: 2017-06 / O controle biológico é considerado uma ferramenta natural e alternativa ecológica para superar os problemas causados pela utilização de métodos químicos no controle de pragas. Além disso, os biocontroladores apresentam inúmeras vantagens quando comparados aos seus análogos químicos, principalmente quanto ao impacto ambiental, custo, manuseio, especificidade e desenvolvimento de resistência. Entre os diversos microrganismos utilizados no controle biológico, os fungos se destacam e, entre estes, o fungo filamentoso e patógeno de artrópodes Beauveria bassiana está entre os mais estudados e aplicados. Neste estudo, utilizando proteômica e ferramentas de bioinformática, foram identificadas um total de 256 proteínas. Proteínas envolvidas em diferentes processos importantes para o biocontrole como degradação da cutícula (proteases, lipases), defesa/antioxidantes (catalases, oxidoredutases) e efetoras (glicosil hidrolases) foram observadas. A maioria destas proteínas parecem ser secretadas, seja por rotas clássicas como não clássicas. A identificação dos mecanismos moleculares de infecção do fungo em pragas específicas possibilita o entendimento mais refinado do biocontrole e, consequentemente, no desenvolvimento de estratégias para otimizar este processo. A identificação de proteínas em um sistema que mimetiza as condições de infecção possibilita a busca orientada de microrganismos mais eficientes com maior virulência e especificidade no controle biológico do artrópode R. microplus. / The biological control is considered a natural and ecological alternative tool to overcome the problems caused by the use of chemical methods in pest control. In addition, the biocontrol presents several advantages when compared to its chemical analogues, regarding to environmental impact, cost, handling, specificity and resistance development. Among microorganisms used in biological control, fungi stand out and, the filamentous fungus and arthropod pathogen Beauveria bassiana. This fungus is one of the most studied and applied worldwide. In this study, using proteomics and bioinformatics approaches, a total of 256 proteins were identified. Proteins involved in different important processes for the biocontroling, including degradation of the cuticle (proteases, lipase), defense/antioxidants (catalases, oxidoreductases) and effectors (glycoside hydrolases) were observed. The identification of the molecular mechanisms involved in the fungal infection on specific pests provides understanding of biocontrol and consequently helping to develop strategies to optimize this process. The identification of proteins in a model that mimics the infection condition enables the oriented search for more efficient micro-organisms with greater virulence and specificity in the biological control of R. microplus tick.

Les insecticides chimiques sont de plus en plus considérés comme des moyens de derniers recours pour lutter contre les populations de ravageurs, car ils augmentent considérablement les coûts de production et que leur usage abusif peut entraîner des effets néfastes sur la santé humaine, animale et environnementale. Dans ce contexte, la recherche de méthode alternative de lutte prend toute son importance afin de remplacer leur emploi par des outils à risque réduit. A l'instar de plusieurs autres insectes, certaines populations de la punaise terne, Lygus lineolaris (Palisot de Beauvois) (Hémiptères: Miridés), qui est un ravageur cosmopolite, phytophage et d'importance économique en Amérique du Nord, sont résistantes à plusieurs pesticides chimiques actuellement homologués. Les microorganismes entomopathogènes occupent une place importante parmi les méthodes alternatives de lutte contre les insectes ravageurs. Le champignon Beauveria bassiana (Balsamo) Veuillemin, est un agent entomopathogène naturellement présent dans les écosystèmes. II offre un potentiel très intéressant pour contrôler les populations de la punaise terne. L'objectif général de cette étude était de mesurer l'impact de l'emploi des préparations insecticides à base de B. bassiana sur les populations de la punaise terne dans les vignobles. La première étape de notre démarche visait à déterminer, à l'aide d'épreuves biologique, la pathogénicité et la virulence (CL₅₀ et TL₅₀) des isolats INRS-CFL et INRS-1P de B. bassiana sur les populations adultes et nymphales de la punaise terne. Les résultats ont montré une susceptibilité des nymphes et des adultes de L. lineolaris soumis aux préparations à base de B. bassiana. La seconde étape de notre démarche, a consisté en l'étude comparative de l'effet de l'application de ces deux isolats de B. bassiana et de l'insecticide chimique cyhalothrin-λ (Matador®) sur les populations des adultes de la punaise terne dans les vignobles. Les résultats ont montré que les mortalités provoquées par B. bassiona étaient comparables à celles obtenues avec le cyhalothrin-λ. Ces résultats suggèrent l'utilisation d'une formulation à base de l'isolat lNRS-CFL de B. bassiana contre les populations adultes de la punaise terne avec une concentration de 5 x 10¹³ conidies/ ha. Nos résultats démontrent aussi que l'activité insecticide des conidies des isolats INRS-IP et INRS-CFL de B. bassiana est maintenue jusqu'a six jours suivant l'application. Des applications multiples sur une base hebdomadaire sont donc requises tout au long de la durée de floraison de la vigne si l'on désire maintenir une activité insecticide permettant de contrôler les populations de la punaise terne. En complément de l'objectif précédent, la troisième étape devait permettre de suivre la persistance des conidies de B. bassiana sur les feuilles de la vigne. La persistance des conidies semble être le facteur déterminant l'activité insecticide des préparations à base de B. bassiana. Ainsi, nos résultats montrent que les conidies des isolats INRS-IP et INRS-CFL de B. bassiana sont présentes durant six jours suite à leur application sur les feuilles des plants de la vigne. Ces résultats mettent en évidence la nécessité d'élaborer une formulation permettant d'accroître la persistance des conidies sur le feuillage augmentant ainsi l'efficacité des applications. La dernière étape avait comme objectif de déterminer l'effet des applications multiples de B. bassiana sur la survie des populations nymphales de L. lineolaris. Le suivi des populations nymphales de la punaise terne par la technique de frappe montre qu'il y a une diminution significative du nombre de nymphes vivantes en fonction du temps. Nos résultats au laboratoire et en champ de la vigne démontrent le fort potentiel de l'agent entomopathogène B. bassiana contre les populations de la punaise terne. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : La punaise terne, Beauveria bassiana, Épreuves biologique, Cyhalothrin-λ, Pathogénicité, Virulence, Activité insecticide, Persistence.

University, Diss., 2003--Heidelberg.

Mycoviruses are viruses that infect and replicate in fungal cells, but unlike most known viruses of plants and animals, they exceptionally produce deleterious effects on their host. Nonetheless, the last discoveries showed that some mycoviruses can decrease the virulence of their phytopathogenic fungal hosts, making them very attractive for their possible use as biological control agents. Most mycoviruses have dsRNA genomes and are widespread in all major taxa of fungi. Beauveria bassiana is one of the most studied species of entomopathogenic fungi; it has a cosmopolitan distribution and is used as biocontroller against invertebrates in agriculture. In the present work, a collection of 137 isolates of B. bassiana obtained at different locations and from different habitats in the Czech Republic was analysed. These isolates were analysed for the presence of dsRNA elements indicative of viral infections. The results revealed a high prevalence of viral infections in Czech B. bassiana isolates, with 22.6% of the isolates containing dsRNA elements with viral characteristics. Obtained dsRNA electropherotypes showed that virus diversity in infected isolates was high and that mixed virus infections occurred among them. Based on the characteristics of the electrophoretic band patterns, it could be hypothesized that B. bassiana isolates collected in the Czech Republic could harbour members of the viral families Totiviridae, Partitiviridae, Chrysoviridae and Hypoviridae.

Made available in DSpace on 2016-08-29T15:36:36Z (GMT). No. of bitstreams: 1 tese_7162_Flavio Neves Celestino.pdf: 2148761 bytes, checksum: a2d59f2bbb6a591a5c583d3df71f8441 (MD5) Previous issue date: 2014-11-28 / A broca-do-café, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae), tem sido a grande responsável por perdas causadas à cafeicultura. Desta forma, tem-se buscado alternativas para o controle dessa praga, tais como os inseticidas botânicos e o fungo entomopatogênico Beauveria bassiana (Bals.) Vuillemin (Ascomycota: Hypocreales). Assim, esse trabalho teve como objetivos: (1) avaliar técnicas de criação da broca-do-café; (2) avaliar a utilização de inseticidas botânicos, óleos minerais e o inseticida contedo azadiractina (ICA); e (3) verificar a compatibilidade in vivo entre o óleo de mamona e o fungo B. bassiana, visando ao manejo de H. hampei. A partir dos resultados, verificou-se que a melhor técnica para criação da broca-do-café é em café robusta em coco, sem a necessidade de qualquer processo de assepsia, podendo ser armazenado em freezer a -20 ºC para ser utilizado durante a entressafra. Com base nos estudos de atividade inseticida, o ICA (3,0% v v-1) e o óleo de mamona (3,0% v v-1) causaram 40,8 e 53,7% de mortalidade da broca-do-café, respectivamente. O extrato da torta da semente de mamona não apresentou toxicidade sobre H. hampei. O óleo de mamona causou a mortalidade da broca-do-café, sendo provavelmente devido ao bloqueio dos espiráculos, impedindo a respiração desse inseto. Óleo de mamona apresentou efeito antagônico sobre B. bassiana reduzindo a mortalidade da broca-do-café. Houve redução da mortalidade de H. hampei causada pela interação entre B. bassiana e o óleo de mamona em função do aumento da concentração do óleo de mamona. Para concentrações mais elevadas de B. bassiana observou-se menor interferência do óleo de mamona. Mediante os resultados encontrados, o manejo de H. hampei pode ser realizado utilizando-se a associação entre o óleo de mamona e o fungo B. bassina, desde que se observe a viabilidade econômica e a concentração de ambos.