Oomycetes in the genus Phytophthora cause devastating diseases worldwide, resulting in billions of dollars of economic damage annually. Although the control of these oomycetes is a high priority, a lack of effective control measures has led to their continued success as pathogens. In this thesis, microfluidic Lab-on-a-chip (LOC) devices containing force sensing micropillars were designed to investigate hyphal force production, a key component of invasive growth. The growth rate, width and force exerted by the hyphae of the pathogen Phytophthora nicotianae were successfully measured on the designed devices. These variables were also measured in hyphae where the actin cytoskeleton was disrupted with latrunculin B. The results identify the critical importance of the actin cytoskeleton in hyphal growth and morphology. In addition, two other pathogens from the Phytophthora genus, Phytophthora cinnamomi and Phytophthora sojae, were successfully grown on the designed devices. This result identifies the applicability of these devices to investigate the molecular mechanisms responsible for force generation in other pathogenic oomycete species.

The knowledge gained from this research contributes to our understanding of the mechanisms that underlie the invasive growth of pathogenic oomycete species. A greater understanding of these mechanisms is required to improve the control strategies of Phytophthora and other pathogenic hyphal organisms. This research highlights the effectiveness of the LOC devices designed in the quest to obtain this knowledge.