Sustainable production of livestock products needs to take account of the environmental consequences of grassland agriculture, the loss of biodiversity in grassland production systems, yet at the same time maintain a level of profitability for livestock farmers. Feeding systems with improved levels of feed conversion that are consistent with DEFRA’s food safety, welfare, economic and environmental objectives are required. Such systems will require improved utilisation of the commonly–employed grasses and legumes as well as the use of alternative legumes, not only as sources of safe, traceable protein but also as suppliers of other nutritional and environmental benefits. This requires the availability of legumes that make more efficient use of nutrients, have the capacity to grow and persist within a diverse sward yet are still productive. This project supports germplasm improvement by contributing to an understanding of the basis of variation within legumes of the key traits that influence nutrient loss, protein protection, biodiversity, soil quality and the relationship with traits important for production, persistence and forage quality. This work will exploit a range of material including novel selection lines, introgression lines and germplasm collected within the UK and will benefit from collaborations with soil scientists and animal scientists at IGER and research in the uplands (LS3646). This project is directed towards the identification of selection criteria for classical germplasm improvement and to facilitate genome mapping and marker assisted selection for the development of improved varieties of white clover and red clover in LS3644 and LS3645 to meet the changing requirements of grassland within the UK beef, sheep and dairy sectors. In addition, research on Lotus will identify the physiological basis for its lack of persistence, poor growth and lack of competitive ability within the sward and help determine the potential for breeding this useful species for UK conditions.