Increasing wheat drought tolerance and recovery throughout the life cycle through regulation of plant growth mechanisms

Water availability is the major universal factor that limits agricultural productivity worldwide. Even in climates like UK it is warned that droughts could devastate food production by the 2020s (UK Government Committee on Climate Change). Current extreme climatic variability is coming at a time when the annual rate of crop yield improvement is not keeping pace with the projected demand for food. New ideas and approaches are required for crop resilience combined with high yield potential. Drought can impact plant growth throughout development, with early vegetative development and reproductive development particularly vulnerable. There is currently no strategy to improve crop drought tolerance at all stages of the life cycle to enable tolerance to and recovery from drought. Genetic modification (GM) has promise because it can speed up and focus genetic changes around single or few genes and mechanisms with the potential to provide step-change yield improvements currently required, but has yet not reached its potential for which we propose new strategies. GM so far has been able to increase abiotic stress tolerance, but mostly with yield penalty when no stress occurs. Growth is particularly sensitive to drought, more so than photosynthesis. We have recently discovered new genes that if targeted correctly can be utilised to improve drought tolerance. However, these genes have not yet been tried in wheat. These are novel plant signalling genes that regulate growth processes during drought itself and recovery from drought during vegetative growth and sucrose allocation to developing seeds during the flowering period or reproductive development. Wheat plants genetically modified for these genes will be subject to drought and drought recovery and the impact on growth, biomass, gene expression, sugars and final yield will be determined. We will also examine genetic variation in genes involved in sucrose allocation and use in wheat populations from International Maize and Wheat Improvement Centre (CIMMYT) in Mexico. This research will provide new knowledge and strategies, new genes, genetic markers and varieties to improve wheat drought tolerance and wheat yields under varying water availability throughout the crop life cycle. Technology will be rapidly deployed into new wheat varieties through knowledge exchange with CIMMYT and industry.

Current extreme climatic variability is coming at a time when the annual rate of crop yield improvement is not keeping pace with the projected demand for food. Drought is the factor worldwide that most limits food production. New ideas and approaches are necessary to increase crop resilience to drought in a way that does not reduce maximum yield potential. In this proposal we consider this in the context of growth mechanisms and management of carbon budgets that regulate resilience, recovery and productivity under drought. In previous BBSRC-funded work in arabidopsis we have discovered that trehalose 6-phosphate (T6P) can regulate both sucrose allocation and use of sucrose once allocated. In relation to this we have shown that T6P can prime gene expression for recovery from stress. Our related research in maize shows substantial improvements in the field under drought through GM of one trehalose pathway gene. Our strategy combines GM of trehalose pathway in wheat with natural variation in trehalose pathway genes in CIMMYT populations and the novel resurrection gene SDG8i involved in strigolactone glycosylation to improve drought tolerance during vegetative and reproductive growth in wheat applicable to UK and to regions where drought can be more extreme. New mechanistic models including data from RNA seq analysis will propose a long-term strategy for productivity of wheat under drought. Technology will be delivered into new wheat varieties involving knowledge exchange with CIMMYT and industry.

Wheat is the major crop in the UK, Europe and in drought-prone parts of the world in North and South America, Middle East, Australia and Russia. It provides a fifth of the world's calories. Drought is the major factor worldwide that limits crop yields accounting for millions of tonnes of grain annually. Any genetic modification through selective breeding or GM that improves drought tolerance is highly desirable. Currently there is no rational GM strategy for the improvement of drought tolerance throughout the crop growth cycle that does not impinge upon maximum yield potential. The work will deliver new technology, molecular markers, varieties for accelerated wheat breeding.

Who benefits
The work impacts food security in the most direct way possible and benefits the whole global community if wheat and other crops can be made more resilient to drought. The focus of the proposal is wheat, but we hypothesise that the mechanisms explored within it are generic and hence could be utilised to improve drought tolerance in other cereals and other crops. The importance of carbon budget management and growth mechanisms has been overlooked in the analysis of drought tolerance. Our related research in maize shows substantial improvements can be obtained in the field through GM of just one trehalose pathway gene. The route to impact in the field and marketplace is already in place through collaboration with CIMMYT who are providing access to germplasm growing in field plots in Mexico. Additionally a large multinational company, Syngenta, with sufficient legal know-how and financial backing to bring GM products and new varieties through conventional breeding to market are associated with the project and will be offered new technology with regard to resurrection genes. The work will impact the field of plant science widely as many researchers are interested in mechanisms that control growth and allocation processes and stress tolerance which involve central regulatory and signalling pathways.

How benefit
Improved wheat yields in the UK will increase economic performance and improve food security. More wheat would be produced for the home market and for export. The collaboration with CIMMYT ensures that new technology can be deployed in areas of the world where drought is especially prevalent. The knowledge gained will also be of importance in understanding more generally the plant regulatory mechanisms that control wheat yield and that of related cereals, which again will be of generic importance to the scientific community and agri-business sector. The timescale of benefits of new drought tolerant wheat varieties is likely to be over the next 5-10 years, although dissemination of new knowledge and technology will begin sooner than this. The researcher employed on the project will gain skills and understanding in methods of modern molecular biology related to crop physiology and how latest GM and molecular breeding approaches can be deployed to improve crops yields. They will travel to CIMMYT to sample field plots. The researcher will learn bioinformatics and use this skill to interpret RNA seq data and build mechanistic models and strategies to improve wheat drought tolerance. Such skills could be utilised in education, public sector institute research, government and advisory boards and agri-business sectors for future employment roles.