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- Context of the research Wheat provides approximately 20% of the calories and protein we consume each day and is a major staple across much of the developing world. As the world population continues to increase, the sustainability of wheat yields must be improved by minimizing losses produced by pathogens. Wheat yellow rust, caused by the fungus Puccinia striiformis (Pst), was recently dubbed one of "wheat's worst enemies" and continues to be a major threat to global food security. This disease is an historical and continuing threat to wheat production, capable of significant reductions in both grain quality and yield in susceptible varieties. The appearance of new and more aggressive Pst strains at the beginning of the 21st century and their rapid spread pose an increasing global threat to wheat production, and have resulted in severe yield losses in recent years. The most economic and environmentally sustainable way to fight yellow rust is by developing wheat varieties that are genetically resistant to the disease. To date, scientist and breeders have deployed resistance genes into agriculture, but with little or no knowledge as to how the pathogen will adapt or respond to them. This inherently 'blind' and inefficient approach has meant that few genes have remained effective in controlling the disease over time. Basically our lack of knowledge of the pathogen's biology and characteristics has meant that we've been fighting with one hand tied behind our backs. Aims and objectives Recent innovations in sequencing technologies, combined with increased knowledge of pathogens in other species, provide us with the unprecedented opportunity to start understanding what makes yellow rust such a devastating disease. We propose to use these new technologies to access the complete DNA sequence of multiple strains of the yellow rust pathogen. We will sequence the most current Pst strains from Africa, India and the UK and also go back in time by sequencing historic collections of yellow rust. These strains, which until now have been stored in the cold, tell the story of how the pathogen has changed in history to become more aggressive and overcome wheat varieties that were thought at the time to be resistant. Sequencing will allow us to identify these changes at the DNA level. Understanding and interpreting these changes will provide the context of how wheat varieties and the fungus have co-evolved across three continents. This information will constitute a very powerful framework to identify wheat genes that will stand a better chance at maintaining their resistance against yellow rust in the future. We will use this knowledge to characterize and introduce new sources of yellow rust resistance into modern wheat varieties which are adapted to the different environments. Through this work, we also seek to create new partnerships between researchers and enhance the scientific capabilities of all partners. Potential applications and benefits This project will provide insight into how the wheat yellow rust pathogen has evolved to overcome previously effective wheat resistance genes and use this information to develop more sustainable strategies for the future. We will work with local breeders to deploy these new resistance genes which will lead to the development of locally adapted wheat varieties with improved potential to maintain resistance in farmers' fields. These improved varieties will have profound implications from a social, economic and environmental perspective. These varieties should improve the sustainability of food crop production systems and contribute to the alleviation of hunger and poverty of small-holder farmers by reducing the risk of crop failure, increasing profit margins, reducing fungicide applications, protecting yield, and extending the life of varieties which farmers have adopted. These varieties should ultimately translate into increased food security and opportunities to improve farmer income.