Microfluidic Sensors for the Detection of Motile Plant Zoospores

Plant pathogen zoospores play a vital role in the transmission of several significant plant diseases, with their early detection being important for effective pathogen management. Current methods for pathogen detection involve labour-intensive specimen collection and laboratory testing, lacking real-time feedback capabilities. Methods that can be deployed in the field and remotely addressed are required. In this proof-of-concept study, we have developed an innovative zoospore-sensing device by combining a microfluidic system that interfaced a flow stream with a microfluidic cytometer, whilst incorporating a chemotactic response as a means to selectively detect motile spores. Spores of Phytophthora cactorum were captured in eddies in a stub at a right-angle bend in a flow channel from which they were able to swim up a detection channel following a gradient of attractant. They were then detected by a transient change in impedance, as measured with a single-chip lock-in amplifier, when they passed between a pair of electrodes. Such a sensing system has a great potential to be further developed into a portable, remotely addressable, low-cost sensing system, offering an important tool for field pathogen real-time detection applications.