Sclerotinia stem rot (SSR), caused by the necrotrophic fungal pathogen Sclerotinia sclerotiorum, is one of the most devastating diseases affecting crops. More than 400 plant species around the globe are affected by this fungus. In canola, one of Canada's most important crops, yield losses due to SSR can be as high as 50%. Although chemical control with fungicides is currently the most common tool for the management of SSR, the routine application without prior information about the risk of the

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... isease development is also financially inefficient. The early prognosis of an outbreak is critical to avoid the severe economic losses caused by SSR and can be achieved by the detection of a small number of S. sclerotiorum airborne ascospores, one of the main agents of infection in stem rot. However, the current lack of simple and effective methods to detect fungal airborne pathogens has hindered the development of an accurate early warning system. In this thesis, we explored the design and development of lab-on-a-chip devices for the detection of S. sclerotiorum ascospores, aiming at their future integration with spore-trap samplers into an effective SSR forecasting system. Our first design is based on a Coulter counter approach, which consists of a microfluidic chip capable of quantifying single ascospores flowing in a microchannel. The target ascospores are injected into the device and selectively captured by dielectrophoresis, while other particles in the sample are flushed away to the outlet drain of the device. Subsequently, the target ascospores are released into the flow stream of the device and are detected when flowing through a constriction employing dynamic impedimetric sensing. Experimental results indicated a Preface This thesis is an original work by Pedro Alejandro Duarte Riveros. Credit to work not conducted by the author himself and acknowledgments were given throughout the thesis in the form of footnotes. Most of the research work described in the chapters of this thesis has been published in authored and co-authored articles.