Master of Science / Department of Agronomy / Allan K. Fritz / Reducing plant disease pressure in wheat (Triticum aestivum L.) is an important management goal for producers. Over the last 10 years, steadily increasing adoption of no-till management has resulted in both over wintering as well as increased inocula levels for many diseases associated with straw residue. Reduced rates of fungicide, applied at early stages of plant development were investigated to measure their effect on reducing inocula density, controlling disease pressure and ultimately increasing grain yield in both no-till and conventionally planted wheat in Kansas from 2004-2008. Different cultivars were chosen based upon their resistance or susceptibility to specific diseases. The main diseases of interest were leaf rust (Puccinia triticina), speckled leaf blotch (Septoria triticii), tan spot (Pyrenophora tritici-repentis), and powdery mildew (Blumeria graminis (DC.) E.O. Speer f.sp. tritici). Two different studies were conducted. In 2004-2007, studies focused on the impact of spraying 133g/ha, half the normal rate, of propiconazole at Feekes 4.0. Disease levels and grain yields were evaluated. In 2008, four fungicide treatments and six cultivars were evaluated at 6 locations. Grain yield, measurements of green leaf duration, and grain yield components were also evaluated. No statistical differences were found in the 2004-2006 studies, but trends were apparent with grain yield increasing by 10.9%. The 2006-2007 growing season was a failure due to a late spring freeze. In the 2007-2008 growing season, statistically different grain yields were observed among some cultivars at two locations. At Partridge, KS and Salina, KS, Jagalene treated with an early-season application of propiconazole yielded significantly more than the untreated check, providing 11.4% and 9.5% increases, respectively. Early fungicide treatments also increased green leaf duration and reduced disease pressure. Further, larger scale studies need to be conducted to more accurate quantify the benefits of early applications of fungicides.

No description available.

Call number: LD2668 .T4 1950 P5 / Master of Science

Bibliography: leaves 186-210. / v, 210 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Environmental Science and Management, 1998

Thesis (Ph. D.)--University of Adelaide, Dept. of Soil Science, 1995? / Copies of author's previously published articles inserted. Includes bibliographical references (leaves 184-197).

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis--Wisconsin. / Vita. Bibliography; leaves 120-130.

Foot rot disease of wheat is caused by the pathogens Fusarium cuImorum, F.avenaceum and Microdochium nivale. Symptoms of foot rot are a general browning of the stem base and leaf sheath. There is a discrepancy between the ability of fungicides to control these pathogens in vivo and in vitro, and no relationship between disease symptom severity and yield loss has been established in wheat. The identification of the causal agents of foot rot disease is not possible from examination of disease symptoms alone. This work showed that the azole fungicides flusilazole and prochloraz inhibited the germination of conidia and mycelial growth of F. culmonon, F. avenaceum and M. nivale in vitro to a varying extent. However, no consistent control of these pathogens in wheat was observed in the field using the same fungicides. Further studies employing a semicontrolled outdoor experiment showed a relationship between density and timing of inoculum application, disease symptom severity and yield loss in wheat artificially inoculated with F. culmorum and M. nivale. Molecular marker systems were used to address the problem of pathogen detection and identification. A Random Amplified Polymorphic DNA (RAPD) assay was developed to differentiate F.culmorum, F.avenaceum and two types of M.nivale (M.nivale var.nivale and M. nivale var .majus) in vitro. Selected RAPD products were cloned and sequenced and species specific primers constructed from this sequence infonnation. These primers were used in the polymerase chain reaction (peR) and were shown to detect the pathogens in host tissue. This technique was adapted by addition of a competitor fragment to the peR reaction resulting in a quantifiable competitive peR assay. Using this method the fungal biomass of each pathogen present in the host tissue could be estimated. The development of these techniques for the identification, detection and quantification of F. cuimorum, F.avenaceum, M.nivale var.nivale and M.nivale var.majus in plant tissue will allow more extensive studies of the epidemiology of these species, the competition between species and the effect of fungicides on these pathogens can be carried out.

Os fungicidas são normalmente utilizados para o controle de doenças causadas por fungos fitopatogênicos em diversas culturas, incluindo frutas. Estes compostos, especialmente os descritos com atividade em múltiplos alvos, podem afetar organismos não alvos como leveduras, levando elas à morte por diferentes vias. O objetivo deste trabalho foi determinar o mecanismo de ação e de morte de três diferentes fungicidas utilizados na viticultura (mancozeb, captan e dithianon) sobre Saccharomyces cerevisiae. Os resultados mostraram que leveduras expostas ao mancozeb (100 µM, 6 h) levam a uma drástica redução da viabilidade, mas sem modificações na integridade da membrana celular. As células tratadas com mancozeb apresentaram marcadores apoptóticos como aumento na concentração intracelular de espécies reativas de oxigênio (ROS), hiperpolarização da membrana mitocondrial e externalização de fosfatidilserina, indicando que a morte celular de S. cerevisiae ocasionada por mancozeb é apoptótica e conforme observado pelo comportamento de linhagens mutantes, segue a via metacaspase dependente. Aproximadamente 80% das leveduras tratadas com captan (20 µM, 6 h) apresentaram disfunções na membrana citoplasmática, e a drástica redução na concentração de grupos tiólicos proteicos e não proteicos. Além disso, as células que mantiveram sua integridade de membrana após a exposição ao captan, exibiram externalização de fosfatidilserina e acumulação de ROS. Mutantes com deleção em YCA1 apresentaram resistência parcial ao captan, indicando a ativação da cascata apoptótica metacaspase dependente. Em fermentações vínicas o captan (2,5 µM) atrasa o início da fermentação de maneira dose dependente, devido à drástica redução na viabilidade celular. Porém, em dosagens subletais, as células remanescentes se adaptam ao fungicida e completam a fermentação sem alterações evidentes nas características físico-químicas do produto final. Da mesma forma, leveduras tratadas com dithianon (2 µM; 3 h) mostraram aumento no número de células com permeabilização da membrana citoplasmática, aumento de ROS e redução na quantidade de tióis, mas sem sinais de apoptose. De forma geral, os resultados indicam que o mancozeb induz apoptose em S. cerevisiae via metacaspase dependente, enquanto o captan leva a morte por necrose e apoptose e o dithianon mata as células por necrose. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2017-05-19T12:14:24Z No. of bitstreams: 1 Dissertacao Fernando Joel Scariot.pdf: 2337872 bytes, checksum: 6074c8b470cfba3f134e8417172b84df (MD5) / Made available in DSpace on 2017-05-19T12:14:24Z (GMT). No. of bitstreams: 1 Dissertacao Fernando Joel Scariot.pdf: 2337872 bytes, checksum: 6074c8b470cfba3f134e8417172b84df (MD5) Previous issue date: 2017-05-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Fungicides are currently used to control fungal phytopathogenic diseases in many crops, including fruits. These compounds, especially those described as multisite activity fungicides, can affect non-target organisms like yeasts leading to their cell death by different pathways. The objective of this work was determining the mechanism of action and death of three fungicides used in viticulture (captan, dithianon and mancozeb) on Saccharomyces cerevisiae. The results showed that yeast exposition to the mancozeb (100 µM, 6 h) lead to a drastic reduction of cell viability, but no modification of cell membrane integrity. Mancozeb treated cells shown apoptotic markers as increase of intracellular reactive oxygen species (ROS), mitochondrial membrane hyperpolarization, and phosphatidylserine externalization, indicating that mancozeb induced cell death in S. cerevisiae is apoptotic and as shown by mutants strains, follow metacaspase-dependent pathway. Almost 80% of captan treated yeasts (20 µM, 6 h) showed citoplasmatic membrane dysfunction, and a drastic reduction on both non-proteic and proteic thiol concentrations. Moreover, the cells that retain their membrane integrity after exposure to the captan exhibited phosphatidylserine externalization and ROS accumulation, indicating apoptosis. YCA1 deletion mutant exhibited partial resistance to captan, suggesting a metacaspase dependent apoptotic cascade. In wine fermentations captan (2,5 µM) delays the beginning of alcoholic fermentations in a dose dependent manner, associated with a drastic reduction on yeast viability. However, in sub-lethal dosages, the reminiscent viable cells adapted to the fungicide, grow and complete fermentation with non-evident modifications on the physicochemical characteristics of the final product. Similarly, yeast cells treated with dithianon (2 µM; 3 h) showed cell membrane permeabilization, ROS increase, and decrease of cellular thiol compounds, but no signs of apoptosis. In general, the results indicated that mancozeb induces metacaspase dependent apoptotic cell death in S. cerevisiae, where captan leads to a dual necrotic and apoptotic cell death, and dithianon kills cells by necrosis.

Orientador: Maria Lucia Ribeiro / Banca: Gilberto Casadei de Baptista / Banca: Rosalinda Carmela Montone / Banca: Ângela Regina Araújo / Banca: Alberto José Cavalheiro / Resumo: Fungicidas, como pirimetanil, fluquinconazol e procloraz, e acaricidas, como clofentezina e cihexatina, são aplicados tanto no período de pré-colheita, como para preservar a qualidade e as características de cor e sabor das frutas durante a armazenagem, o transporte e a comercialização (procloraz). Contudo, devido à persistência dos seus resíduos nas frutas, monitoramentos devem ser realizados, empregando-se técnicas analíticas sensíveis, para avaliar se os resíduos de tais pesticidas atendem aos limites estabelecidos pelas legislações dos países exportadores e importadores. Um número reduzido de métodos para análise de resíduos dos fungicidas pirimetanil, procloraz e fluquinconazol e dos acaricidas cihexatina e clofentezina, usados no controle de doenças e pragas em culturas de frutas, estão descritos na literatura. Aliando este dado à importância econômica da produção de frutas em nosso país, foram desenvolvidos e/ou adaptados métodos eficientes, rápidos e simples para a determinação destes fungicidas e acaricidas na casca e na polpa de mamão (papaia), manga e laranja e no fruto inteiro de morango e uva. As metodologias são baseadas em extração líquido-líquido e análise individual por cromatografia a gás com detecção por captura de elétrons para procloraz e cihexatina e detecção termiônica...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Fungicides, as pyrimethanil, prochloraz and fluquinconazole, besides acaricides, as clofentezine and cyhexatin, have been used to preserve the quality of perishable fruits during their production, storage and commercialization. Also, these fungicides and acaricides are employed in the pre-harvest period. However, the presence of pesticide residues in fruits representes a serious problem, once the pesticides could become a risk to human consumption. So, the development of analytical methods looking for a rapid screening can ensure that the pesticide concentrations are below of the maximum residue limits allowed by the regulatory agencies. In the literature, some methods for the determination of pyrimethanil, prochloraz, clofentezine and cyhexatin in fruit matrices have been described. Respecting fluquinconazole, there is only a German review. Considering the subjects mentioned and that Brazil plays an important role in the worldwide production of fresh fruit, the purpose of this work was to develop simple and efficient methods for the determination of these fungicides and acaricides in peel and pulp of papaya, mango and orange, besides in grape and strawberry (entire fruit). The methodologies are based on liquid-liquid extraction. The analyses were performed by means of gas chromatography with thermionic specific detection for pyrimethanil and electron-capture detection for prochloraz and cyhexatin. In addition, pyrimethanil, prochloraz, fluquinconazole and clofentezine were analyzed employing a liquid...(Complete abstract, click electronic access below) / Doutor