Phytophthora species are plant pathogens that cause considerable damage to agrosystems and ecosystems, and have a major impact on the economy. Infection occurs when their biflagellate zoospores move and reach a root on which they aggregate. The communication between the plant and the zoospores and how this communication modifies the behavior of the swimming zoospores is not yet well characterized.

I will show that using a microfluidic device comprising a growing Arabidopsis thaliana root, we are able to study the kinetics of Phytophthora parasitica zoospores approaching the root and aggregating on the elongation zone, in real time. The experiments show that the kinetics is modified only below a distance of about 300 μm from the elongation zone, with a decrease in the speed coupled with an increase in the number of turns made. In addition, the rate of aggregation is constant throughout the experiment, approximately one hour, and depends on the density of zoospores. The rate is consistent with a random encounter of zoospores with the root, indicating that no long distance signal is evidenced in our experiments.