O Brasil, maior produtor mundial de cana-de-açúcar, produzirá cerca de 642 milhões de toneladas em 9 milhões de hectares plantados da cultura na safra 2014/2015. A cana-de-açúcar, assim como a maioria das culturas semi-perenes, naturalmente perde produtividade ao longo dos cortes e o setor canavieiro se preocupa com a longevidade dos canaviais, que é limitado, entre outros fatores, por doenças bióticas. O raquitismo das soqueiras (Ratoon Stunting Disease - RSD) é considerada a doença mais importante da cultura por causar significativas perdas em produtividade. O agente causal do RSD é a bactéria Leifsonia xyli subsp. xyli (Lxx); o gênero é cosmopolita e apresenta inúmeras espécies. No entanto, a subespécie Lxx tem como único hospedeiro natural conhecido a cana-de-açúcar. O estudo de hospedeiros alternativos deste patógeno reveste-se de importância pela possibilidade de outras espécies servirem como fonte de inóculo para a cana-de-açúcar e também pela possibilidade da descoberta de um hospedeiro experimental que permita o estudo do RSD em condições experimentais mais favoráveis do que a cana-de-açúcar. O presente trabalho realizou um levantamento de possíveis hospedeiros alternativos de Lxx cultivados a partir de sementes ou coletados em áreas de cultivo de cana-de-açúcar empregando pares de primers desenvolvidos especificamente para a bactéria. O trabalho também objetivou analisar o desenvolvimento de três genótipos de sorgo após inoculações artificiais com Lxx. A bactéria não foi detectada em todos os vinte e sete hospedeiros analisados, sendo vinte e duas espécies de gramíneas, confirmando que seu único hospedeiro é a cana-de-açúcar. Por outro lado, Lxx infectou as três espécies de sorgo e causou significativa redução tanto em altura como em diâmetro das plantas comparado a plantas não infectadas. Conclui-se, portanto, que Lxx não coloniza naturalmente várias gramíneas, no entanto diferentes genótipos de sorgo podem ser usados como hospedeiros experimentais para estudos de RSD. / Brazil is the main world producer of sugarcane, with a predicted production of 642 million tons in approximately 9 million hectares in the 2014/2015 harvest. As most semi-perennial crops, its productivity is reduced along successive cropping (ratoons). Thus, increasing the longevity of sugarcane crops, which is limited by biotic diseases, is an important goal for Brazil´s sugar industry. Ratoon stunting disease (RSD) is considered the most important disease of sugarcane because it causes significant losses in productivity. RSD is caused by the bacteria Leifsonia xyli subsp. xyli (Lxx), a cosmopolitan genus with numerous species. However, to date sugarcane is the only known natural host of this pathogen. Identifying alternative hosts of Lxx is important not only because they might represent an additional source of inoculum but also because some might represent a better working model to the study of RSD than sugarcane. This study carried out a PCR-based screening of potential Lxx hosts with primers developed to specifically detect Lxx, using as source seeds or plant specimens collected in sugarcane fields. The effect of artificial inoculations of Lxx on the growth of three sorghum cultivars was also analyzed. Lxx was not detected in all twenty-seven alternative hosts tested, out of which twenty represented grass species, thus confirming the specificity of the Lxx-sugarcane relationship. In addition, Lxx infected the three sorghum genotypes and significantly reduced their height and diameter when compared to non-infected plants. It is concluded that Lxx does not infect other grass species; however sorghum genotypes can be used as experimental hosts in the study of RSD.

Cette thèse s'articule autour de l'optimisation électro-optique des OLEDs (Organic Light Emitting Device) via le développement de méthodes et d'outils de simulation. La modélisation électrique des OLEDs est complexe et sujette à recherche. Au début de la thèse, aucune simulation électrique des OLEDs de l'état de l'art n'avait été présentée jusqu'alors. Le développement d'une simulation, fondée sur des données expérimentales, contribuerait à l'établissement d'une modélisation prédictive, pour une meilleure compréhension et une R&D plus efficace. Dans un premier temps, une méthode d'extraction des paramètres de transport des matériaux utilisés est développée par fit (reconstitution des résultats expérimentaux par simulation) via la fabrication de dispositifs spécifiques. Lesdites valeurs, extraites et comparées selon deux modèles de mobilité, ont assurées la constitution d'une base de données. L'emploi de celle-ci a permis la réalisation de la simulation, complète et à plusieurs températures, du comportement électrique d'une OLED entière. L'étude minutieuse des profils intrinsèques simulés a servi à relever une accumulation de charges à l'interface de recombinaison, néfaste à l'évolution dans le temps des performances du dispositif. Dans un second temps, nous nous sommes proposé de solutionner le problème par la création d'un mélange bipolaire, afin d'élargir le profil de recombinaison. Après optimisation du mélange au sein de l'OLED, une augmentation de durée de vie à mi luminance de ca. +30% a été mise en évidence, de même qu'une stabilisation en tension du point de couleur. Pour approfondir la compréhension des mécanismes en jeu, la caractérisation TOF-SIMS d'empilements organiques a fait l'objet d'études. Les premiers résultats, très encourageants, ont permis la reconstitution entière du profil chimique de l'empilement OLED. Une deuxième série de résultats a démontré la possibilité de détecter les molécules organiques telles qu'évaporées, qui donnera accès à des informations plus poussées sur la dégradation des matériaux. Enfin, une cathode alternative en WO3/Ag/WO3 (WAW) a été optimisée par simulation dans le but de démontrer l'importance de l'augmentation du coefficient d'extraction de lumière. La réalisation des dispositifs a permis de démontrer une hausse de la luminance et de l'efficacité de 40% due à la cathode, en accord avec la simulation. Le transfert du point de procédé sur une machine de catégorie industrielle a résulté en la fabrication de dispositifs OLED avec cathode WAW présentant une augmentation de la durée de vie à mi luminance de +75% par rapport à la référence. / The work presented here revolves around electrical and optical optimization of OLEDs (Organic Light Emitting Device) through the development of simulation methods and tools. The electrical modeling of OLED is a complex field, belonging to R&D. At the beginning of this work, no state of the art OLED electrical simulation has been presented yet. The development of simulation, based on experimental data, would contribute to the establishment of predictive simulation, allowing a better understanding and faster R&D cycles. Firstly, an extraction method for organic semiconductors' transport parameters has been developed by fit procedure (reconstitution of experimental results with simulation). The extracted values, compared between the two mobility models, were used to compile a database. These sets allowed the realization of the simulation at various temperatures of the electrical behavior of a complete OLED stack. The careful analysis of the simulated intrinsic profiles gave an insight on charge accumulation at the recombination interface, harmful for the lifetime performance of the device. Secondly, we proposed to solve the problem with a bipolar blend to enlarge the recombination profile. After optimization of the blend inside the OLED, an increase of the lifetime of ca. +30% has been highlighted, as well as the stabilization of the color point dependency to voltage. To further understand the mechanisms related to the insertion of this layer, TOF-SIMS characterization of organic layers was studied. Very promising early results allowed the profiling of a full OLED stack, and determination of each layer. A second wave of results, bound to Ar beam analysis, demonstrated the possibility to detect undamaged molecule signatures, giving access to far more degradation related information than before. Finally, an alternative cathode made of WO3/Ag/WO3 (WAW) has been optimized for white OLED microdisplays to enhance the light outcoupling coefficient. The fabrication of the devices demonstrated a +40% increase in luminance and current efficiency, in perfect agreement with simulation. The transfer of the process onto an industrial class deposition cluster tool resulted in the fabrication of OLEDs with WAW cathodes demonstrating a +75% increase of the lifetime at half luminance.

Background: Engaging in sharing economy practices has in recent years increased in popularity. Hence, renting a private home instead of traditional accommodation options are becoming more common among travellers. Previous research has focused on the demand side of renting accommodations. The suppliers' perspective has also been developed and researched regarding their intentions to continue renting out their properties. However, non-experienced hosts have previously been neglected in academic research. Therefore, this thesis focuses on non-experienced hosts and their thoughts regarding opening their home and their intention to engage in sharing economy practices.  Purpose: The purpose of this study is to explore how the different factors guide Swedish ‘småhus’ owners' intention to rent out their primary residence.  Method: To explore the purpose of this thesis, a qualitative research design was chosen. The empirical data was gathered through fifteen semi-structured interviews sampled through non-probability judgemental sampling. An abductive research approach was chosen to analyse and interpret the data using thematic analysis.  Conclusion: This study found that participants' intentions to act as hosts were guided by attitude, subjective norms and perceived behavioural control presented through the theory of planned behaviour. Participants further showed that trust, concerns, control, privacy, economics, environment, security, and people were themes that affected some- or all ‘småhus’ owners' intentions in this research. Furthermore, this study found that economic benefit acts as the largest motivator to act as hosts, especially where an economic need exists. However, trust was deemed necessary to enable most participants to consider the idea of opening up their private homes.

Cultivation of Napier grass, Pennisetum purpureum, the most important livestock crop in East Africa is severely constrained by Napier Grass Stunt (NGS) disease. The disease spreads via an insect vector or vegetative propagation of infected plant material and is caused by a phytoplasma. This necessitates the development of an integrated management approach for the disease. Therefore, objectives of this study were to assess the incidence of the disease and its severity, to identify its wild hosts and farmers‟ knowledge on these hosts, to assess the threat of NGS disease to cultivated grasses and to establish the role of wild inoculum sources in its spread. The study showed NGS incidence ranging from 33% in Uganda to 95% in Kenya with 49% of the farmers interviewed, being able to discern NGS disease by its symptoms. Most farmers cited roguing and use of alternative fodder grasses as control measures, making these strategies the likely components of an integrated management approach for the disease. Responders named Sedge grass (Cyperus spp.) and Star grass (Cynodon dactylon) as the likely hosts of diseases caused by phytoplasma. Phytoplasmas were detected in leaves of 11 of 33 wild grass species collected using polymerase chain reaction (PCR) based on the highly conserved phytoplasma-specific 16S ribosomal DNA fragment. Sequence determination of amplified PCR fragments revealed the presence of NGS-related phytoplasmas in 11 grass species, Bermuda grass white leaf (BGWL) phytoplasmas in three and goosegrass white leaf (GGWL) in two wild grass species, showing that the geographical distribution and diversity of phytoplasmas and their grass hosts are greater than previously thought. The relationships between NGS and Hyparrhenia grass white leaf (HGWL) phytoplasmas were determined using sequences based on secA gene and immunodominant protein (imp). Results showed a very low genetic diversity between NGS and HGWL and produced a phylogenetic tree congruent to that produced by the 16S, affirming the inclusion of HGWL in the 16SrXI group. NGS phytoplasma was transmissible to food crops through Maiestas banda Kramer (Hemiptera: Cicadellidae) under screen-house conditions. With 56.3%, Saccharum officinarum showed the highest infection level followed by Eleusine coracana with 50%, Sorghum bicolor with 43.8%, Oryza sativa with 31.3% and Zea mays with 18.8%. All the phytoplasma-infected plants were asymptomatic except S. officinarum plants, which showed mild to moderate symptoms consisting of foliar yellow leaves and bright white or yellow midribs. This hints that besides wild hosts, food crops may also serve as alternative source of inoculum enabling a complex NGS disease cycle, which may add to challenges in the development of the disease control strategies. However, failure by M. banda to transmit HGWL and BGWL phytoplasmas back to Napier grass is an indication that it could be the exclusive vector of NGS. Therefore, there is need to initiate transmission trials using planthoppers and leafhoppers occurring on HGWL and BGWL phytoplasma-infected grasses to determine whether insect vectors capable of transmitting phytoplasmas from native grasses to Napier grass, are present in the region. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Cultivation of Napier grass, Pennisetum purpureum, the most important livestock crop in East Africa is severely constrained by Napier Grass Stunt (NGS) disease. The disease spreads via an insect vector or vegetative propagation of infected plant material and is caused by a phytoplasma. This necessitates the development of an integrated management approach for the disease. Therefore, objectives of this study were to assess the incidence of the disease and its severity, to identify its wild hosts and farmers‟ knowledge on these hosts, to assess the threat of NGS disease to cultivated grasses and to establish the role of wild inoculum sources in its spread. The study showed NGS incidence ranging from 33% in Uganda to 95% in Kenya with 49% of the farmers interviewed, being able to discern NGS disease by its symptoms. Most farmers cited roguing and use of alternative fodder grasses as control measures, making these strategies the likely components of an integrated management approach for the disease. Responders named Sedge grass (Cyperus spp.) and Star grass (Cynodon dactylon) as the likely hosts of diseases caused by phytoplasma. Phytoplasmas were detected in leaves of 11 of 33 wild grass species collected using polymerase chain reaction (PCR) based on the highly conserved phytoplasma-specific 16S ribosomal DNA fragment. Sequence determination of amplified PCR fragments revealed the presence of NGS-related phytoplasmas in 11 grass species, Bermuda grass white leaf (BGWL) phytoplasmas in three and goosegrass white leaf (GGWL) in two wild grass species, showing that the geographical distribution and diversity of phytoplasmas and their grass hosts are greater than previously thought. The relationships between NGS and Hyparrhenia grass white leaf (HGWL) phytoplasmas were determined using sequences based on secA gene and immunodominant protein (imp). Results showed a very low genetic diversity between NGS and HGWL and produced a phylogenetic tree congruent to that produced by the 16S, affirming the inclusion of HGWL in the 16SrXI group. NGS phytoplasma was transmissible to food crops through Maiestas banda Kramer (Hemiptera: Cicadellidae) under screen-house conditions. With 56.3%, Saccharum officinarum showed the highest infection level followed by Eleusine coracana with 50%, Sorghum bicolor with 43.8%, Oryza sativa with 31.3% and Zea mays with 18.8%. All the phytoplasma-infected plants were asymptomatic except S. officinarum plants, which showed mild to moderate symptoms consisting of foliar yellow leaves and bright white or yellow midribs. This hints that besides wild hosts, food crops may also serve as alternative source of inoculum enabling a complex NGS disease cycle, which may add to challenges in the development of the disease control strategies. However, failure by M. banda to transmit HGWL and BGWL phytoplasmas back to Napier grass is an indication that it could be the exclusive vector of NGS. Therefore, there is need to initiate transmission trials using planthoppers and leafhoppers occurring on HGWL and BGWL phytoplasma-infected grasses to determine whether insect vectors capable of transmitting phytoplasmas from native grasses to Napier grass, are present in the region. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Parasitic insects are known for their distinct life strategy: they necessarily kill their hosts in order to complete their life cycle. Eighty percent of parasitoids species belongs to the order Hymenoptera (bees, ants and wasps). Among parasitoid wasps Ichneumonidae stands out with more than 25 thousand species and a great diversity of habits and hosts. Despite the large number of species already described, there is a low representativeness of species in tropical regions, mainly due to the lack of taxonomical studies in those areas. The objective of the present study was to compile the information on the biology of Ichneumonidae through an extensive literature review and to conduct a taxonomic study of the species of Charops Holmgren, 1859 (Campopleginae) occurring in Brazil. It was observed that out of the 950 species of Ichneumonidae registered in Brazil, less than 10% present some host records. These records are mainly concentrated in the south and southeast of the Brazil where the relatively largest number of taxonomists are concentrated. In addition, most of the records relate to hosts of economic importance in corn, soybean and cotton crops. Little is known about the parasitoid / host interaction in natural Brazilian biomes. Also, thirty-three species with dubious occurrence in Brazil were found. Notwithstanding Campopleginae being one of the subfamilies with the highest number of host records, taxonomical studies on it are still scarce in Brazil. An example is the genus Charops, which despite having recorded for Brazil at genus level, has never been studied through a taxonomic point of view. The study of 614 specimens of this genus revealed 9 new species from Brazil, being the first described for South America. Its geographical distribution record is expanded and illustrated in distribution maps. High resolution images and a key for these species are also provided. / Insetos parasitoides são conhecidos pela sua distinta estratégia de vida, na qual para concluir o seu ciclo de vida necessariamente matam os seus hospedeiros. Oitenta por cento das espécies de parasitoides pertencem à ordem Hymenoptera (abelhas, formigas e vespas). Dentre as vespas parasitoides destaca-se a família Ichneumonidae, que possui mais de 25 mil espécies nominais e apresenta grande diversidade de hábitos e hospedeiros. Apesar do grande número de espécies já descritas, existe uma baixa representatividade de espécies conhecidas de regiões tropicais devido, principalmente, à escassez de estudos taxonômicos na região. O presente estudo teve por objetivo compilar as informações sobre a biologia de Ichneumonidae a partir de uma extensa revisão da literatura e realizar um estudo taxonômico das espécies de Charops Holmgren, 1859 (Campopleginae) que ocorrem no Brasil. Foi observado que cerca das 950 espécies de Ichneumonidae que ocorrem no Brasil, menos de 10% possuem algum registro de hospedeiro. Tais registros estão concentrados principalmente nas regiões sul e sudeste do Brasil aonde se concentra a maior quantidade de taxonomistas do país. Além disso, grande parte dos registros referem-se a hospedeiros de importância econômica nas culturas de milho, soja e algodão. Pouco se sabe sobre a interação entre parasitoides/hospedeiros em biomas naturais brasileiros. Foram encontradas 33 espécies que apresentam registro de ocorrência dúbio para o Brasil. Apesar de ser uma das subfamílias com maior número de registros de hospedeiro, Campopleginae permanece relativamente carente de estudos taxonômicos no Brasil. Um exemplo disso é o gênero Charops que apesar de apresentar registros para o Brasil (em nível de gênero), nunca foi estudado através de um viés taxonômico. O estudo de 614 exemplares deste gênero revelou 9 espécies novas para o Brasil, sendo estas as primeiras espécies descritas para a América do Sul. Sua distribuição geográfica conhecida foi ampliada e ilustrada em mapas de distribuição. Imagens de alta resolução e uma chave de identificação para essas espécies são fornecidas.

O estudo das fontes alimentares em culicídeos possui evidentes significados ecológicos e epidemiológicos, pois auxilia na identificação de animais possivelmente envolvidos na manutenção de surtos epidêmicos das doenças transmitidas por vetores, oferecendo informações para a indicação de potenciais reservatórios de patógenos. Entre os métodos utilizados para avaliar o possível grau de atração exercido por certas fontes de alimentação em relação às fêmeas de culicídeos, a técnica de Reação em Cadeia da Polimerase (PCR) se destaca como sendo uma das técnicas mais eficientes na detecção de repastos sanguíneos devido à alta sensibilidade e especifidade. O objetivo desse estudo foi descrever o perfil alimentar das fêmeas de culicídeos capturadas nos parques Alfredo Volpi, Anhanguera, Carmo, Chico Mendes, Ibirapuera, Santo Dias e Shangrilá, situados na cidade de São Paulo, investigando possíveis associações entre as espécies de mosquitos e suas respectivas fontes alimentares, analisando assim o comportamento no âmbito alimentar dessas espécies em diferentes localidades da cidade, durante os meses de Fevereiro de 2011 à Fevereiro de 2012. A identificação do repasto sanguíneo foi realizada por meio da técnica de PCR para os seguintes hospedeiros: aves, cães, gatos, humanos, primatas ( não humanos) e roedores em 510 fêmeas ingurgitadas distribuídas em 14 espécies capturadas pleas técnicas de aspiração, CDC copa, CDC solo e armadilha de Shannon. Dos vertebrados, apenas o hospedeiro gato não foi encontrado como sendo fonte de repasto, as demais têm sido utilizadas como fontes de alimentação para os culicídeos nos parques estudados. Baseando-se em testes estatísticos não se encontrou nenhuma tendência de associação entre as espécies de culicídeos capturadas ingurgitadas e as fontes utilizadas para repasto, evidenciando assim, padrões aleatórios por parte dos mosquitos em se alimentarem de fontes sanguíneas mais abundantes ou mais fáceis de serem abordadas, reforçando a característica oportunista das fêmeas de culicídeos em busca das suas fontes de alimentação sanguíneas. Sendo de fundamental importância tais informações em contexto epidemiológico, afim de, identificar novos possíveis hospedeiros e reservatórios de patógenos em cadeias de transmissão de doenças transmitidas por culicídeos / The study of the blood meal sources in culicids has evident ecological and epidemiologic meanings, because assists in the identification the possible animals involved in maintenance of epidemic outbreaks of the vector-borne diseases, offering information to indicate the potential pathogen reservoirs. Among the methods used to evaluate the possible degree of attraction exercised by certain source of meals relative to culicid females, the Polymerase Chain Reaction (PCR) stands out, because it is a more efficient technique in blood meals detected, due to the high sensitivity and specificity. The aim of this study was to describe the food profile of culicid females captured in the Alfredo Volpi, Anhanguera, Carmo, Chico Mendes, Ibirapuera, Santo Dias and Shangrilá parks, located in São Paulo city, investiganting possible associations between mosquito species and their blood meal sources, analyzing the feeding behavior of these species in different localities of city, during the months February 2011 and February 2012. The identification of blood meals was realized by PCR technique for the following vertebrate hosts: avian, dogs, cats, humans, primates (non-human) and rodents in 510 engorged females distributed in 14 species captured by aspirator technique, cup CDC, soil CDC and Shannon trap. Of vertebrates, only cats were not found as source of meal, while the others have been used as blood meals for mosquitoes in the parks. Based in statistical tests, there was no trend of association between culicid engorged species captured and sources of meals, thus evidencing random patterns of mosquitoes to feed on the blood meal sources more abundant or easiest to the addressed, reiforcing the opportuinistc characteristic of the mosquito females in searching blood meals. Being of fundamental importance such information in epidemiological context, in order to identify new hosts and pathogen reservoirs in the chains of transmission of vector borne diseases

A doença conhecida como enfezamento vermelho, associada a um fitoplasma do grupo 16SrI, subgrupo B, foi relatada em áreas brasileiras cultivadas com milho ainda no início da década de setenta. A importância econômica da doença se expressou a partir da década seguinte, com a introdução dos plantios de safrinha. O patossistema tem sido muito explorado em termos de pesquisa, porém falhas no conhecimento ainda são significativas. No presente trabalho foi investigada a sobrevivência do fitoplasma e da sua cigarrinha vetora Dalbulus maidis em algumas espécies forrageiras de alto interesse agronômico. Para isto, foram utilizadas cinco variedades de capim Panicum maximum cv. Mombaça, P. maximum x P. infestum cv. Massai, Brachiaria bizantha cv Marandu, B. brizantha cv. Piatã e B. decumbens cv. Basilisk (popularmente conhecida por Decumbens), os quais foram inoculados com o fitoplasma por meio de insetos infectivos alimentados em plantas de milho comprovadamente portadoras do patógeno. As avaliações foram realizadas tomando-se como critérios a detecção do fitoplasma nos tecidos dos capins, usando a técnica molecular de PCR, e a contagem diária do número de cigarrinhas mortas encontradas nas plantas forrageiras inoculadas. Amostragens de tecidos para a detecção do patógeno foram feitas aos 28, 56, 84, 112 e 140 dias após a inoculação, sendo as plantas cortadas para posterior rebrota, após cada amostragem. Também foi conduzido um ensaio em que cigarrinhas foram alimentadas em todas as variedades de forrageiras, portadoras do fitoplasma e, em seguida, confinadas em plantas sadias de milho. Os resultados revelaram que o fitoplasma estava presente em todas as plantas das diferentes variedades de capim, aos 28 dias após a inoculação. Aos 56 dias após a inoculação, o fitoplasma foi detectado em 66% das plantas de Marandu, 50% das plantas de Massai e 16% das plantas de Decumbens, Mombaça e Piatã. Aos 84, 112 e 140 dias após a inoculação, o patógeno não foi mais detectado nos tecidos rebrotados das plantas amostradas. Quanto à sobrevivência da cigarrinha, os capins se comportaram similarmente, dentro de cada um dos períodos de avaliação correspondentes a 24, 48, 72, 96 e 120 horas após o confinamento dos insetos nas plantas; no período de 120 horas, praticamente todos os insetos estavam mortos. Em relação à infecção de plantas de milho por insetos alimentados em plantas forrageiras portadoras do patógeno, os dados evidenciaram ausência do fitoplasma em todas as plantas de milho inoculadas. Estes resultados evidenciaram que, em condições naturais, provavelmente, as forrageiras podem servir como reservatórios; no entanto, sugerem que estas forrageiras podem não atuar como fonte de inóculo do patógeno para plantas de milho. Ainda, os dados apontaram que nenhuma das variedades testadas se destacou como sendo mais favorável à sobrevivência do vetor. / Maize bushy stunt, associated with a phytoplasma of the group 16SrI, subgroup B, has been reported in Brazilian areas cultivated with corn since 1970s.The economic importance of the disease was expressed from 1980s, with the introduction of a cultivation system named \"safrinha\" maize. The pathosystem has long been explored, but failures of knowledge are yet significant. In the present work it was investigated the survival of the fitoplasma and its vector, the leafhopper Dalbulus maidis, in various forage species of high agronomic interest. So, five varieties of forage (Panicum maximum cv. Mombaça, P. maximum x P. infestum cv. Massai, Brachiaria bizantha cv Marandu, B. brizantha cv. Piatã e B. decumbens cv. Basilisk (popularly known by Decumbens) were used, which were inoculated with the phytoplasma via infective insects fed in corn plants infected by the pathogen. Assessment was conducted based on the detection of phytoplasma using PCR tecnique and daily counting of dead leafhoppers found in the inoculated forage plants. Tissues were collected for detection 28, 56, 84, 112 and 140 days after inoculation and plants were cut immediately after each sampling. In addition, an assay was conducted, in which insects were fed in infected plants belonging to all forage varieties and, subsequently, confined in healthy corn plants. The results allowed to detect the phytoplasma in all distinct forage varieties, 28 days after inoculation. Assesment made to the 56 days allowed to detect the pathogen in 66% of the plants of Marandu, in 50% of Massai, and 16% of plants of the varieties Decumbens, Mombaça and Piatã. In evaluations conducted to the 84, 112, and 140 days after inoculation, the phytoplasma was not more detected in the new tissues from forage plants. Concerning survival of leafhoppers, the different forage showed the same behavior, within each period corresponding to 24, 48, 72, 96 e 120 hours after confining of the insects in the plants; in the period of 120 hours, almost all insects were dead. In relation to the infection of corn plants by insects fed in forage plants infected with the pathogen, the analysis showed absence of the phytoplasma in all inoculated corn plants. These results pointed that, in natural conditions, probably the forages to serve as reservoir; however, they also suggested that these forages probably do not act as inoculum sources of the pathogen for corn plants. In addition, the results also demonstrated that none variety stood out as more favorable to survival of the leafhopper.

<div> In computer networks, the convenient internet access facilitates internet services, but at the same time also augments the spread of malicious software which could represent an attack or unauthorized access. Thereby, making the intrusion detection an important area to explore for detecting these unwanted activities. This thesis concentrates on combining the Model and Instance Based Machine Learning for detecting intrusions through a series of algorithms starting from clustering the similar hosts. </div><div> Similar hosts have been found based on the supervised machine learning techniques like Support Vector Machines, Decision Trees and K Nearest Neighbors using our proposed Data Fusion algorithm. Maximal cliques of Graph Theory has been explored to find the clusters. A recursive way is proposed to merge the decision areas of best features. The idea is to implement a combination of model and instance based machine learning and analyze how it performs as compared to a conventional machine learning algorithm like Random Forest for intrusion detection. The system has been evaluated on three datasets by CTU-13. The results show that our proposed method gives better detection rate as compared to traditional methods which might overfit the data.</div><div> The research work done in model merging, instance based learning, random forests, data mining and ensemble learning with regards to intrusion detection have been studied and taken as reference. </div>

The reemergence of Goss’s wilt of corn in the western Corn Belt in 2006, along with subsequent identification of the disease in 16 states, has led to renewed interest in the disease and its epidemiology. Goss’s wilt, caused by the bacterium Clavibacter nebraskensis, is currently the third-leading cause of yield loss in corn from diseases in the United States. Its impact is exacerbated by the fact that cultural control methods are the only current means for its control. The objectives of our research were to (1) determine the role that alternative hosts of the bacterium play in the disease cycle and epidemiology of Goss’s wilt, and (2) determine if postemergence herbicide use affects disease severity. Through a greenhouse experiment, we discovered three new weedy alternative hosts of the disease. In a series of field and greenhouse experiments, we found that C. nebraskensis can overwinter on alternative host and corn debris in Indiana. We found that C. nebraskensis did not become seed-borne in alternative hosts. In contrast to corn, no systemic infections were observed on alternative hosts, with the bacterium being restricted to inoculated leaf tissue. Using herbicides to control C. nebraskensis-infected weeds did not reduce the pathogenicity of the bacterium recovered from treated plants. The use of nicosulfuron, dicamba plus diflufenzopyr, and a 2X rate of glyphosate postemergence increased disease severity in one experiment, but postemergence herbicides did not influence disease severity in a second experiment. Corn yield was not affected. This indicates that herbicide use may play a role in the epidemiology of Goss’s wilt in some years, but ultimately corn yield is not affected. Our results demonstrate that the host range of C. nebraskensis is wider than previously thought, and that postemergence control of alternative hosts may not be sufficient in reducing inoculum levels. Our results suggest that failure to control alternative hosts could negate some of the benefits of crop rotation to reduce inoculum levels in a field, thus playing an important role in the epidemiology of Goss’s wilt. <br>