Advances in breeding for enhanced iron and zinc concentration in common bean in Eastern Africa.

Micronutrient malnutrition is one of the most serious health challenges facing vast sectors of Africa's population particularly resource-poor women and children. Main deficiencies include iron, zinc and vitamin A. Plant breeding has frequently been advocated as the most sustainable strategy of providing varieties of different food crop species with enhanced micronutrient density to combat the global hidden hunger problem which affects more than 2 billion people. However, there are few research programs which have implemented this approach from concept stage to finished products which can be widely disseminated and commercialised to create meaningful impact. The East African bean biofortification program offers a case study of such a program. The aim of this program was to develop well adapted, high yielding, Fe and Zn rich bush and climbing bean cultivars and agronomic approaches that enhance expression of high mineral trait. The objective of this review is to provide a synthesis of the progress made in the last 22 years, with a focus on genetic diversity, inheritance and bioavailability of Fe and Zn, cooking quality, and to identify research gaps and suggest future directions.