Investigating the role of electrotaxis in Phytophthora root infection

Tens of billions of dollars are lost annually to crop diseases caused by Phytophthora spp. This coupled with the growing world population and the reduction of cultivable land calls for a drastic improvement in the field of crop protection. Currently the only available strategies to tackle Phytophthora outbreaks are manual removal of infected plants or preventative spraying of generic fungicides. The problem is exacerbated by the continual emergence of fungicide-resistant strains. Introduction of a reliable form of crop protection is therefore necessary and urgent.
The spores of some Phytophthora spp. have been shown to be electrotactic, in other words to accumulate at one pole when exposed to an electric field. Phytophthora palmivora zoospores in particular are anodotactic as they accumulate at the negative pole. It has also been shown that the roots of several plant species are characterised by a distinctive electrical signature, it is thus likely that zoospores exploit the host's electrical signature for targeting. Therefore, removing or attenuating the root electrical signature could critically impair the infection mechanism. Since these signature root currents are constituted by the movement of ions in the environment external to the root, we propose to apply an external electric field to displace these ions thus decreasing the signal of the roots electrical signature. This would in turn decrease Phytophthora's ability to target the root thus preventing infection.
We will use fluorescent microscopy to characterise the electrotactic response curve of P. palmivora zoospores in order to better understand to which electrical power they are most responsive. We will then use 3D printed plant nurseries to apply external electric fields to roots and monitor their health using lightsheet microscopy. This will allow us to assess to what level we can disturb the root's endogenous current without affecting the plant's overall health and in particular its yield. We will then combine the use of lightsheet microscopy and infection assays to identify an electric field regime that will maximise the plant's health and minimise Phytophthora's infection. All of these experiments will be carried out in hydroponic cultures, they will then be repeated in soil and the electrical regime adjusted to account for higher resistance. We aim to achieve a regime that will prevent P. palmivora root infections.