Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Os fungos micorrízicos arbusculares (FMA) têm papel fundamental na absorção de nutrientes, sobrevivência vegetal e na estruturação dos solos. Recentemente uma série de pesquisadores verificou que plantas associadas com FMA também podem se associar com os fungos de micélio escuro (DSE do inglês, dark septate endophytes). Embora de estudo recente, já se observou que os endófitos de micélio escuro igualmente podem promover o crescimento de plantas em diversos ambientes. O objetivo desse trabalho é realizar um levantamento de espécies de FMA e DSE em áreas de Mata Atlântica em um gradiente altitudinal, podendo advir respostas de relevância ecológica maior, como a influência da planta hospedeira, dos parâmetros do solo, da sazonalidade e da altitude sobre a ocorrência e diversidade desses fungos. Espera-se também esclarecer melhor a lacuna existente no conhecimento dos benefícios dos DSE para as plantas e dar o primeiro passo para a compreenção da interação dos FMA com os DSE. Avaliaram-se os atributos químicos, físicos e microbiológicos do solo e, entre estes, a ocorrência e diversidade dos FMA e DSE na raiz e solo rizosférico de diferentes espécies arbóreas da Mata Atlântica do Parque Estadual da Serra do Mar, Estado de São Paulo, Brasil, em um gradiente altitudinal: 80m, 600m e 1000m. As coletas de solo e raízes foram realizadas em quatro estações. Os dados foram submetidos à análise de variância ANOVA, teste LSD, análise canônica discriminante (ACD) e análise de redundância (RDA). Uma vez que muitas espécies de DSE são conhecidas por serem patogênicas sobre certas plantas, os isolados de DSE foram avaliados quanto à sua eventual patogenicidade. Os isolados não patogênicos foram selecionados para um bio-teste, sozinhos ou em combinação com um FMA em plantas de arroz. Foram identificadas no solo rizosférico 58 espécies de FMA e os gêneros Acaulospora e Glomus foram dominantes, enquanto que nas raízes, apenas 14 grupos de FMA foram encontrados e todos apresentaram elevada similaridade com a família Glomeraceae. Foram encontrados 251 isolados de DSE que se agruparam em 35 UTO. A maioria dos isolados de DSE foram patogênicos para as plantas de arroz. A época de amostragem teve efeito sobre a colonização radicular e diversidade dos FMA. A altitude foi importante em selecionar espécies de FMA e também agiu sobre o número de esporos e colonização por DSE e FMA. A maioria dos FMA e DSE ocorreu de forma generalizada nas diferentes espécies hospedeiras, apesar de existirem algumas espécies fúngicas com preferências para certas árvores. Os atributos do solo tiveram forte influência sobre a colonização pelos FMA, enquanto que para os DSE as diferenças na colonização foram pouco infuenciadas pelos parâmetros do solo. No entanto, as propriedades do solo foram responsáveis por dirigir a ocorrência de certas espécies de FMA e DSE. A interação entre FMA e DSE e os seus benefícios para as plantas hospedeiras ainda necessita de maiores estudos principalmente com relação a compreenção das condições fornecidas em experimentos que favoreçam ambas as associações. / Arbuscular mycorrhizal fungi (AMF) play a fundamental role in the absorption of nutrients, plant survival and soil structure. Recently a number of researchers found that plants associated with AMF may also be associated with dark mycelium fungi. In a recent study, it was observed that the dark septate endophytes (DSE), usually Ascomycetes, can promote the growth of plants in different environments. The aim of this study was to survey the diversity of AMF and DSE in Atlantic Forest areas in altitudinal gradients, which result in responses of greater ecological relevance, as the influence of the host plant, soil attributes, seasonality and altitude on occurrence and diversity of these fungi. We also expect to clarify the gap in the knowledge of the benefits of DSE for plants and take the first step towards the comprehension of the interaction of AMF and DSE. We evaluated the chemical, physical and microbiological attributes, and among these, the occurrence and diversity of AMF and DSE in the root and rhizospheric soil of different tree species of the Atlantic Forest of Serra do Mar State Park, State of Sao Paulo, Brazil, along an altitudinal gradient: 80m, 600m and 1000m. Samplings of the soil and roots were performed in four seasons. The data were submitted to ANOVA, LSD test, canonical discriminant analysis (CDA) and redundancy discriminant analysis (RDA). Since many species of DSE are known to be pathogenic on certain plants, DSE fungal isolates were evaluated for their eventual pathogenic activity. The isolates non-pathogenic were used in a bio-test to either alone or in combination with the AMF in rice plants. In the rhizosphere 58 AMF species were identified. The genera Acaulospora and Glomus were predominant. However, in the roots, only 14 AMF sequences were found and all had high similarity to the family Glomeraceae. In an analysis of the DNA ITS sequences of the 251 DSE isolates we found that they clustered into 35 UTOs. Most DSE found were considered pathogenic for rice. The season had no effect on root colonization and AMF diversity. Altitude was important in selecting AMF species and also acted on the number of spores and colonization by AMF and DSE. Most of the AMF and DSE were generalists, without a specificity for host plants, although there are some fungal species with preferences for certain trees. The soil properties had a strong influence on colonization by AMF while, for the DSE, differences in colonization do not seem to be related to soil attributes. However, soil attributes were responsible for directing the diversity of AMF and also of DSE species. The interaction between AMF and DSE and their benefits to the host plants require further studies to comprehend the conditions that favor both associations.

Os fungos micorrízicos arbusculares (FMA) têm papel fundamental na absorção de nutrientes, sobrevivência vegetal e na estruturação dos solos. Recentemente uma série de pesquisadores verificou que plantas associadas com FMA também podem se associar com os fungos de micélio escuro (DSE do inglês, dark septate endophytes). Embora de estudo recente, já se observou que os endófitos de micélio escuro igualmente podem promover o crescimento de plantas em diversos ambientes. O objetivo desse trabalho é realizar um levantamento de espécies de FMA e DSE em áreas de Mata Atlântica em um gradiente altitudinal, podendo advir respostas de relevância ecológica maior, como a influência da planta hospedeira, dos parâmetros do solo, da sazonalidade e da altitude sobre a ocorrência e diversidade desses fungos. Espera-se também esclarecer melhor a lacuna existente no conhecimento dos benefícios dos DSE para as plantas e dar o primeiro passo para a compreenção da interação dos FMA com os DSE. Avaliaram-se os atributos químicos, físicos e microbiológicos do solo e, entre estes, a ocorrência e diversidade dos FMA e DSE na raiz e solo rizosférico de diferentes espécies arbóreas da Mata Atlântica do Parque Estadual da Serra do Mar, Estado de São Paulo, Brasil, em um gradiente altitudinal: 80m, 600m e 1000m. As coletas de solo e raízes foram realizadas em quatro estações. Os dados foram submetidos à análise de variância ANOVA, teste LSD, análise canônica discriminante (ACD) e análise de redundância (RDA). Uma vez que muitas espécies de DSE são conhecidas por serem patogênicas sobre certas plantas, os isolados de DSE foram avaliados quanto à sua eventual patogenicidade. Os isolados não patogênicos foram selecionados para um bio-teste, sozinhos ou em combinação com um FMA em plantas de arroz. Foram identificadas no solo rizosférico 58 espécies de FMA e os gêneros Acaulospora e Glomus foram dominantes, enquanto que nas raízes, apenas 14 grupos de FMA foram encontrados e todos apresentaram elevada similaridade com a família Glomeraceae. Foram encontrados 251 isolados de DSE que se agruparam em 35 UTO. A maioria dos isolados de DSE foram patogênicos para as plantas de arroz. A época de amostragem teve efeito sobre a colonização radicular e diversidade dos FMA. A altitude foi importante em selecionar espécies de FMA e também agiu sobre o número de esporos e colonização por DSE e FMA. A maioria dos FMA e DSE ocorreu de forma generalizada nas diferentes espécies hospedeiras, apesar de existirem algumas espécies fúngicas com preferências para certas árvores. Os atributos do solo tiveram forte influência sobre a colonização pelos FMA, enquanto que para os DSE as diferenças na colonização foram pouco infuenciadas pelos parâmetros do solo. No entanto, as propriedades do solo foram responsáveis por dirigir a ocorrência de certas espécies de FMA e DSE. A interação entre FMA e DSE e os seus benefícios para as plantas hospedeiras ainda necessita de maiores estudos principalmente com relação a compreenção das condições fornecidas em experimentos que favoreçam ambas as associações. / Arbuscular mycorrhizal fungi (AMF) play a fundamental role in the absorption of nutrients, plant survival and soil structure. Recently a number of researchers found that plants associated with AMF may also be associated with dark mycelium fungi. In a recent study, it was observed that the dark septate endophytes (DSE), usually Ascomycetes, can promote the growth of plants in different environments. The aim of this study was to survey the diversity of AMF and DSE in Atlantic Forest areas in altitudinal gradients, which result in responses of greater ecological relevance, as the influence of the host plant, soil attributes, seasonality and altitude on occurrence and diversity of these fungi. We also expect to clarify the gap in the knowledge of the benefits of DSE for plants and take the first step towards the comprehension of the interaction of AMF and DSE. We evaluated the chemical, physical and microbiological attributes, and among these, the occurrence and diversity of AMF and DSE in the root and rhizospheric soil of different tree species of the Atlantic Forest of Serra do Mar State Park, State of Sao Paulo, Brazil, along an altitudinal gradient: 80m, 600m and 1000m. Samplings of the soil and roots were performed in four seasons. The data were submitted to ANOVA, LSD test, canonical discriminant analysis (CDA) and redundancy discriminant analysis (RDA). Since many species of DSE are known to be pathogenic on certain plants, DSE fungal isolates were evaluated for their eventual pathogenic activity. The isolates non-pathogenic were used in a bio-test to either alone or in combination with the AMF in rice plants. In the rhizosphere 58 AMF species were identified. The genera Acaulospora and Glomus were predominant. However, in the roots, only 14 AMF sequences were found and all had high similarity to the family Glomeraceae. In an analysis of the DNA ITS sequences of the 251 DSE isolates we found that they clustered into 35 UTOs. Most DSE found were considered pathogenic for rice. The season had no effect on root colonization and AMF diversity. Altitude was important in selecting AMF species and also acted on the number of spores and colonization by AMF and DSE. Most of the AMF and DSE were generalists, without a specificity for host plants, although there are some fungal species with preferences for certain trees. The soil properties had a strong influence on colonization by AMF while, for the DSE, differences in colonization do not seem to be related to soil attributes. However, soil attributes were responsible for directing the diversity of AMF and also of DSE species. The interaction between AMF and DSE and their benefits to the host plants require further studies to comprehend the conditions that favor both associations.

Four levels of NaNO2 (0 ppm, 50 ppm, 100 ppm, and 156 ppm) were tested for antibotulinal activity in ground pork inoculated with spores of Clostridium botulinum either at the time of formulation or after cooking. Samples formulated with less than 156 ppm sodium nitrite received additional nitrite to adjust the residual nitrite equal to that found after cooking in samples formulated with 156 ppm nitrite. All samples were subjected to abusive storage at 27 C. Inoculating the spores at the time of formulation resulted in a faster rate of swelling. Heating C. botulinum spores for 30 min. at 77 C before addition to cooked meat also resulted in rapid germination. Total botulinal counts were significantly higher (p=0.05) in these samples, compared with similarly treated samples formulated with unheated spores. Samples formulated with 50 ppm initial sodium nitrite and with 78 ppm additional NaNO2 after cooking were the most inhibitory. Initial nitrite concentration was shown to be important for inhibition of C. botulinum growth, probably because of the inhibitory carryover effects of protein-bound nitrite formed during cooing, as well as influencing the concentration of residual nitrite.

Phytophthora pini Leonian, recently re-established from P. citricola I, is a pathogen with a wide range of forest and nursery hosts. It causes foliar infections in horticultural nurseries in Oregon, where recirculating irrigation systems are common. Increased use of recirculating irrigation systems may contribute to disease caused by waterborne plant pathogens. Simulated nursery chamber experiments were utilized to investigate the relationship between Phytophthora pini zoospore inoculum dose and disease on Rhododendron. Disease incidence in this system was unexpectedly low despite high inoculum levels tested, so further experiments under lab conditions were conducted to explore possible causes. Detached leaf assays were conducted to determine how inoculum dose, leaf wounding, and agitation of zoospore inoculum affected foliar infection of Rhododendron. Wounded and nonwounded leaves were dipped into suspensions of zoospores that were either untreated, mechanically agitated by vortexing to cause encystment, or pumped through an irrigation sprayer system. Disease severity (lesion area) and incidence (number of lesions per leaf area) were measured over seven days. At inoculum levels of ���10,000 propagules/mL, motile zoospores infected both wounded and nonwounded leaves. Vortexing or pumping resulted in zoospore encystment, and inoculation with these treatments caused disease almost exclusively on wounded leaves. No disease symptoms were observed following inoculation with any inocula at ��� 2,000 propagules/mL. Scanning electron microscopy of leaves inoculated with encysted propagules showed germinated cysts with hyphae growing over and around stomata without entering leaf tissue until reaching a wound site. Nonwounded leaves inoculated with motile spores showed stomata penetrated by hyphae. These findings indicate the importance of zoospore motility in reaching suitable infection sites, and demonstrate the impact of zoospore encystment on disease development. This has implications for disease management in nurseries where pruning wounds are common and the pumping of infested irrigation water may influence zoospore motility and infectivity. / Graduation date: 2013

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Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

The processes involved in the enhancement of the fluorescence profile of dipicolinic acid (DPA) were measured and analysed, with particular emphasis on their potential application to the rapid identification of suspicious powders. The research was conducted in contribution to the anthrax detector currently under development at this department. Using the enhancement of fluorescence as a method of determining whether a sample contains spores shows great potential because DPA is not found in most powders that do not contain spores. Thus, its detection is a good indication of the presence of spores. The research presented in this thesis primarily focuses on the optimisation of measurement and enhancement techniques. Both DPA and milk powder (containing spores) were used as anthrax simulants. We found that 210 nm light was the optimal wavelength for the enhancement of DPA; however, as most light sources have a higher intensity at longer wavelengths, the use of 270 nm light may be more effective. At low concentrations, there is a linear relationship between detected fluorescence intensity and the quantity of DPA present. A linear response was also found to the enhancement-light exposure time.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Dallas G. Hoover, Dept. of Animal & Food Sciences. Includes bibliographical references.