Photodynamic inactivation of phytopathogens

Supervisors: Maurice P Gallagher, Neil Havis

Project description:

Population growth is projected to rise globally by 30% by 2050, with increase in food requirements of > 60%. Phytopathogens (particularly fungi) represent a major source of crop and seed loss or spoilage, with global losses estimated at ~40% for major crops such as potatoes (Oerke, E. (2006) J. Agric.Sci. 144(1), 31-43). Moreover, effective chemical-based, pathogen treatments are extremely limited and continue to diminish against a tide of rapidly emerging resistance. There is thus a pressing need for alternative disease control methods which can be adapted for modern crop production and storage. Recent advances in antimicrobial light-based strategies have proved highly effective for reducing levels of nosocomial contamination and infections by human fungal and bacterial pathogens (Maclean, M, et al. (2013) J Infect. Preven. 14, 176–181) and similar approaches could be exploited in the crop and food industries. A number of phytopathogens represent targets for such an approach because of their unique chromophore contents which provide selective target for photodynamic therapy. In recent studies, the Gallagher lab (unpublished data) have shown that near infrared light of fixed wavelengths can substantially reduce pathogen levels for organisms such as Staph. aureus, using a proprietary biofilm model (Dall, G et al., J Microbiol Meth.142, 46-51 (2017)). The current project aims to evaluate the effectiveness of light of fixed wavelengths (from visible and nIR spectra) for eliminating major crop or seed disease/spoilage pathogens. We will focus initially on Fusarium and Microdochium species on cereals and Phytopthora infestans and Fusarium species on potatoes as model organisms (in which the applicants have extensive expertise (Osborne, LE & Stein JM. Intl J Food Micro 119, 103-108; Abbas MF et al., Mycopath 11, 45-50.)) because of their disease relevance. Initially, pathogens (in vegetative and spore form) will be screened for reduction in viability with an array of high intensity, light producing diodes of fixed wavelength. Effective wavelengths will then be refined for dose and intensity, blending wavelengths where synergy is indicated.  Subsequently, the approach will be extended to colonised plant tissues models, monitoring impact on infectivity and also measuring indicators of plant health (e.g. germination of infected cereal seed and seed tubers after treatment, and via DNA quantification of fungi). The project should result in novel strategies for disease and spoilage prevention which can be adapted technologically by the Agri-Food industry for enhancing food production, storage, and extending shelf-life. The outcomes of the study will be reported via scientific publications, conferences, meetings & workshops for the academic community, primary producers, agronomists, and relevant stake-holder companies. Outreach communication to the public will include information presentations at ‘doors open days’, SRUC trial open days, disease roadshows, and via social media platforms and institution web sites. Relevant technological developments will be considered for Knowledge Transfer schemes by UofE/SRUC. Both supervisors have long-standing histories of successful PhD training. The student will be registered as part of the UofE Ph.D training scheme but will also benefit from exposure to the many crop-related activities of SRUC.

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