Control of plant diseases such as potato late blight relies heavily on the use of crop protection products such as fungicides. New fungicides are constantly needed as older products face pathogen resistance to them, tighter regulation, and the desire for products with improved environmental and toxicological profiles. Consequently, there is a large global market for crop protection chemicals, which was valued at over $55 billion in 2018.
SEFARI research in this area has used our growing knowledge of the potato late blight pathogen to identify aspects of its biology that could be exploited to better control of this economically important crop disease.
StageWork in Progress
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Crop losses due to disease can severely impinge on farm income locally, and food security on a global scale. Potato late blight caused by Phytophthora infestans is notorious for its role in the 19th century Irish Potato Famine and it is still widely regarded as the most damaging disease of potato crops, causing over $5 billion in direct losses and control costs worldwide every year (£50 million in the UK). Due to Scotland’s climate being conducive to disease development, late blight has a large effect on the 25000+ hectares sown with potatoes each year.
Late blight can be controlled by resistance in potato cultivars, or by the application of crop protection chemicals. Modern crop protection chemicals are highly specific and act at very low application rates. However, chemical control carries the risk that new strains of P. infestans may arise that can overcome the control measures. There is therefore a need to keep one step ahead of this destructive pathogen by identifying new targets for its control using chemicals specific to this and closely related pathogens.
Developing a new crop protection chemical can cost over $250 million and takes over a decade on average. A limiting step can be the identification and validation of suitable targets in the pathogen. We are using our knowledge of pathogen biology to identify and validate new targets for chemical control, and new tools for determining the mode of action of crop protection chemicals.
Our understanding of late blight biology has increased greatly in recent years, driven by the use of genome sequencing. We have focused on determining which cellular pathways are present and active in the different life stages of the pathogen. Analysis of this data has revealed potential targets for control. We can test these targets in the laboratory by knocking them out (and thus inactivating them) to assess their effect on growth and infectivity of the pathogen. We can also test a range of generic (off the shelf) chemicals that are not specific to late blight to demonstrate that a pathogen target can be reached and inactivated, thus validating it for development of more specific agrochemicals.
We are accumulating evidence that a biochemical pathway involved in late blight pathogen metabolism, and not targeted by existing crop protection chemicals, may represent a novel target for crop protection. Other targets are being identified through research into specific aspects of late blight biology. For example, P. infestans uses a specific pathway to deliver small proteins called effectors into plant cells to drive disease development, making it a good target for development of inhibitor chemicals.
A further aspect to developing new crop protection agents is the development of tools that can assist in identifying their effects on pathogens. We are developing a set of laboratory strains for which specific cellular structures are fluorescently labelled to allow us to microscopically follow the effects of control chemical application on late blight.
Figure: Confocal microscope image of actively growing Phytophthora infestans hyphae with the microtubule network fluorescently labelled. Microtubles are the target of some crop protection chemicals used to control late blight and other crop diseases caused by Phytophthora species.
Bringing a new crop protection product to market is both costly and time consuming. New crop protection products are needed to replace older products for which pathogen resistance is a problem, or those that are phased out due to tighter regulations. By identifying and validating (de-risking) new biological targets for developing crop protection chemicals, our work has the potential to reduce the time and cost in the development of new products.
Our work on developing new tools for use in crop protection research also links to and benefits other research areas such as identifying plant disease resistance and understanding how Phytophthora infects plants (e.g. ‘The search for crop pathogens’ Achilles heels’ and ‘Protecting Potatoes - Scotland's Story’).
This work is strongly linked to the crop protection industry, and we collaborate closely with companies in this sector. Our SEFARI research has enabled us to secure further funding that also involves industry partners, which is facilitating the uptake of our findings.
Staff involved in this project have joint appointments with the University of Dundee Division of Plant Sciences.
- Devastating intimacy: the cell biology of plant–Phytophthora interactions
- The Phytophthora infestans Haustorium Is a Site for Secretion of Diverse Classes of Infection-Associated Proteins
- Delivery of cytoplasmic and apoplastic effectors from Phytophthora infestans haustoria by distinct secretion pathways