Advances in breeding for enhanced iron and zinc concentrations in common bean in eastern Africa

Micronutrient malnutrition is one of the most serious health challenges facing vast sectors of the population of Africa, particularly resource-poor women and children. The main deficiencies include iron (Fe), zinc (Zn), and vitamin A. Plant breeding has frequently been advocated as the most sustainable strategy to provide varieties of different food crop species with enhanced micronutrient density to combat the global hidden hunger problem which affects >2 billion people. However, there are few research programmes which have implemented this approach, from concept stage to finished products, which can be widely disseminated and commercialized to create meaningful impact. The east African bean biofortification programme offers a case study of such a programme. The aim of this programme was to develop well-adapted, high-yielding, Fe- and Zn-rich bush and climbing bean cultivars and agronomic approaches that enhance expression of the 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, bioavailability of Fe and Zn, and cooking quality, as well as to identify research gaps and suggest future directions.