Modern agriculture and conventional breeding and the liberal use of high inputs has resulted in the loss of genetic diversity and the stagnation of yields in cereals in less favourable areas. Increasingly landraces are being replaced by modern cultivars which are less resilient to pests, diseases and abiotic stresses and thereby losing a valuable source of germplasm for meeting the future needs of sustainable agriculture in the context of climate change. Where landraces persist there is concern that their potential is not fully realised. Much effort has gone into collecting, organising, studying and analysing landraces recently and we review the current status and potential for their improved deployment and exploitation, and incorporation of their positive qualities into new cultivars or populations for more sustainable agricultural production. In particular their potential as sources of novel disease and abiotic stress resistance genes or combination of genes if deployed appropriately, of phytonutrients accompanied with optimal micronutrient concentrations which can help alleviate aging-related and chronic diseases, and of nutrient use efficiency traits. We discuss the place of landraces in the origin of modern cereal crops and breeding of elite cereal cultivars, the importance of on-farm and ex situ diversity conservation; how modern genotyping approaches can help both conservation and exploitation; the importance of different phenotyping approaches; and whether legal issues associated with landrace marketing and utilisation need addressing. In this review of the current status and prospects for landraces of cereals in the context of sustainable agriculture, the major points are the following: (1) Landraces have very rich and complex ancestry representing variation in response to many diverse stresses and are vast resources for the development of future crops deriving many sustainable traits from their heritage. (2) There are many germplasm collections of landraces of the major cereals worldwide exhibiting much variation in valuable morphological, agronomic and biochemical traits. The germplasm has been characterised to variable degrees and in many different ways including molecular markers which can assist selection. (3) Much of this germplasm is being maintained both in long-term storage and on farm where it continues to evolve, both of which have their merits and problems. There is much concern about loss of variation, identification, description and accessibility of accessions despite international strategies for addressing these issues. (4) Developments in genotyping technologies are making the variation available in landraces ever more accessible. However, high quality, extensive and detailed, relevant and appropriate phenotyping needs to be associated with the genotyping to enable it to be exploited successfully. We also need to understand the complexity of the genetics of these desirable traits in

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This study was undertaken to explore the relation between auto-, allo-and nil-competition using a long established pure line cultivar of bread wheat, where genes controlling yielding and competing ability co-exist and co-interact . The investigation lasted three growing periods, the first two with trials grown at nilcompetition (100 cm), and the third with trials grown at the three conditions of competition . In the first growing period, divergent single plant honeycomb selection for high and low yield was applied in the cultivar Siete Cerros, to continue in the second growing period with divergent line honeycomb selection . In the third growing period, top and bottom lines selected under nil-competition were compared with the mother variety Siete Cerros under auto-, allo-and nil-competition .Correlation coefficient estimates between auto-, allo-and nil-competition demonstrated that auto-competition and nil-competition are correlated positively interse and negatively with allo-competition . In general, the results suggest that yielding and competing ability are correlated negatively .The implications of the findings are discussed in relation to the possibility of (1) selecting for heritable high yield on a single plant basis, (2) avoiding biased results due to interplot competition, (3) substituting cultivar degeneration for cultivar improvement .