In the drylands of Africa, land degradation and soil fertility depletion are major threats to natural resource conservation and food security. A potential solution is to exploit the properties of native N 2 -fixing legume trees. One candidate is Acacia senegal, the main species producing the internationally traded 'gum arabic', which also provides a multitude of ecosystem services and supports the livelihoods of many impoverished rural populations in the drylands of sub-Saharan Africa. The development of improved planting stock would help meet the demand for reliable, high quality gum and, at the same time, could enhance income generation and promote wide-scale planting giving environmental benefits for the fragile drylands ecosystem. This requires a strategic improvement programme, but traditional breeding methods require significant time. Molecular approaches are frequently touted as providing a means of increasing efficiency in breeding programmes; however it is as yet unclear whether they can deliver this efficiency, particularly in the regions in which A. senegal is an important crop. Here we review the status of genetic improvement of A. senegal highlighting modern molecular approaches to advance the breeding efforts for gum and other important traits to enhance adaptability and sustainable management of genetic resources in the changing global climate.

This chapter reviews the principles of resource capture in intercropping and agroforestry systems. It also examines the role of roots and shoots in overcoming the constraints to crop production imposed by hostile and infertile environments with a view to ensuring sustainable food production to meet the needs of predicted future increases in human populations.

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