Engineering synthetic symbioses between plants and bacteria to deliver nitrogen to crops

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Nitrogen is one of the main constraints on agricultural productivity so its use is essential for high crop yields. In a world where food security is now considered a national priority crop yield is of critical importance. However, the drive for yield alone has led to very high application of nitrogen with consequent nitrate contamination of groundwater and problems of eutrophication. The problem is so serious that reactive nitrogen in the biosphere has doubled from preindustrial levels primarily through massive inputs into agriculture. It also results in the production of N2O which is around 300 times more potent than CO2 as a greenhouse gas. These are problems of regional, national and international scope that require urgent amelioration and are at the forefront of the grand challenges for UK science. By improving our understanding of how rhizobia develop into N2 fixing bacteroids in legume nodule we acquire the understanding to improve the competitive success of desirable strains of Rhizobium. It also lays down a foundation of understanding for the transfer of bacteria to nodules in other plants such as cereals. These aims are long term but ultimately this work has relevance to farming practice as well as government policy in decisions about nitrogen utilization in agriculture. It is also relevant to UK attempts to reduce greenhouse emissions and produce a low carbon economy. Understanding the nitrogen fixation and its role in the nitrogen cycle in agricultural has wider benefits applicable to the UK public because of its importance in food security and meeting international obligations for mitigating the effects of climate change. We propose to reach a wide audience of farmers, the public, national and international policy makers and charitable institutions through active outreach (Friends of John Innes). We also have strong links with "The Nitrous Oxide Focus Group" and the newly formed "Consortium for Legumes in Agriculture, Society and Environment", which is an international consortium to promote understanding on the use of legumes. In addition we have broad links to the environmenral impact of this work through the Earth and Life Systems Alliance between JIC and UEA (ELSA) and to the UK government via the "Living With Environmental Change program (LWEC)" which has its secretariat at UEA.