Engineering wheat for take-all resistance

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Take-all disease has a substantial impact on wheat yield throughout the cereal-growing areas of the world and is a major threat to food security. The cost of this fungal disease to wheat production in the UK is estimated at £85-340m per annum. Take-all is a ubiquitous and chronic problem that that imposes serious limitations on wheat production as roughly half of UK wheat crops are affected. Introduction of genes through conventional breeding strategies relies on the identification of resistances through screening, and subsequent crossing into elite varieties, and is the approach taken in the wheat pre-breeding LoLa (BB/J004596/1). Our proposal takes a complementary approach that involves the direct introduction of cloned genes for take-all resistance into wheat through genetic modification (GM) which has the potential for more rapid delivery of useful genes into elite wheat varieties.

We have assembled a customised toolkit for triterpene metabolic engineering in plants consisting of characterised genes and enzymes from oat and other plant species. Our aim is to engineer single and multiple steps for triterpene synthesis into hexaploid wheat and evaluate the consequences of this for triterpene production, plant performance and take-all resistance. The development of methods for high-efficiency transformation of wheat with multiple genes within this proposal will lay the foundation for introduction of other valuable multi-gene traits/processes (e.g. nitrogen fixation, C4 photosynthesis, polygenic pest/pathogen resistance, seed micronutrient content) into wheat in the future.

The key deliverables and outcomes of this research programme will be:
1. Evaluation of a transgenic approach to engineer wheat for the synthesis of protective triterpenes;
2. Establish a multi-gene wheat transformation platform;
3. Provide industry with a potential solution to take-all disease;
4. Training of project scientists in cross-disciplinary and applied crop research

The most important impact of this research will be the evaluation of a metabolic engineering strategy for control of take-all disease of wheat. This has the potential to provide the plant breeding industry with a strategy for disease control that will complement longer-term strategies currently being initiated within the wheat pre-breeding LoLa. There are many environmental and economic costs associated with take-all that have a detrimental effect on the overall competitiveness and sustainability of the UK arable industry. Introduction of take-all resistance into cultivated wheat will have a profound impact on reducing these negative externalities across the production sector.

We expect there to be a number of different beneficiaries of the proposed work. These will include the private sector in the form of wheat farmers and breeding companies, the UK environment, policy makers, and the wider public in general. Many of the expected benefits will be shared between groups and we have outlined some of these below:

- Increased yields: At least half of UK wheat crops are affected by take-all, with average yield losses between 5-20% and complete failure of the crop under severe take-all conditions. The average UK wheat production value is ~£1.7 b. Therefore the minimum cost of take-all to the UK arable industry is between £85m - 340m per annum. The availability of take-all resistant wheat would significantly reduce this loss and provide increased flexibility to farmers.
- Testing the potential of GM approaches: This work will test the potential of a GM approach to take-all control. The multi-gene wheat transformation platform established within this programme will provide cutting-edge enabling technology for academic researchers and industry for future wheat improvement for disease resistance and other important traits/processes (e.g. nitrogen fixation).
- More efficient use of nitrogen fertilization: Take-all disease leads to reduced uptake of nitrogen by the roots. Not only is this inefficient and costly but the remaining nitrogen leaches into farmland water courses, so contributing to pollution and eutrophication. Improving resistance to take-all would therefore have both direct financial benefits (reduced nitrogen requirements of second and third wheat crops) and indirect consequences of improving nitrate utilisation, reducing wastage and increasing overall competitiveness of UK wheat growers.
- More efficient land use: Improved take-all resistance will result in increased yields in second and third wheat situations, enabling more wheat to be produced from the same amount of land. This will help in the sustainable intensification of UK agriculture, increasing the efficiency of land use and providing farmers with enhanced flexibility in their farm management practices.
- Training the next generation of crop scientists: This proposal brings together a unique combination of disciplines that will provide an exciting training ground for the project scientists involved. The resulting innovation and training will provide the next generation of skilled crop scientist, with benefits beyond the plant breeding industry, and boosting the UK economy.