WP4 will identify selection criteria (traits) and ideotypes to breed for species adapted for mixtures, screen varieties within the existing genetic resources and start breeding programs and develop a novel approach of phenotyping to propose new and original breeding schemes to breed plant types for species mixtures. Experiments will be conducted in multi-site field trials in experimental stations for testing/screening varieties, breeding lines, landraces and heterogeneous populations (including traditional varieties) of several grain legumes, cereals and other companion species (species used to produce ecosystem services but not harvested). WP4 will also make use of participatory approaches where farmers and breeders participate in selection trials in conventional and organic farming and in testing different spatial designs of species mixtures.