Abiotic stress tolerance is genetically complex, displaying continuous variation because the effects of individual genes (so called Quantitative trait loci), cannot be discerned. The aim of this project is to deploy genetic and genomic tools to map and clone such genes. This is an essential prerequisite for understanding their modes of action and making them available as targets for genetic manipulation by plant breeders. The work has particular emphasis on wheat since this is the UK's most important agricultural crop. The work is focused on conditions where limited availability of nirogen and water reduces grain yield.