Buying maize from a roadside vendor. Biofortified maize is key to addressing vitamin-A deficiency in many Africans, especially women and children. Photo by O Adebayo, IITA.

Nutrition studies have shown that over 100 million Africans who rely heavily on cereal-based diets such as maize have sub-optimal vitamin A intake. Due to vitamin A deficiency, these people have high risk of visual impairment and blindness, and increased susceptibility to diseases such as anemia, diarrhea, measles, malaria and respiratory infections. Young children, pregnant women and lactating mothers are especially vulnerable. In Africa, an estimated 33 million preschool-aged children are reported to be deficient in vitamin A.

To address this, we undertook research to develop tropical maize that is genetically fortified with increased levels of vitamin A. By introducing and crossing maize from the temperate zones that contain high levels of beta-carotene with tropical maize having intermediate pro-vitamin A content, we were able to produce inbred lines that contain high levels of both nutrients.

We further evaluated and crossed these improved lines with cultivars that are well-adapted to the prevailing diseases of maize. After repeated selection for desirable agronomic traits and resistance to diseases at the different stages of inbreeding, we were able to produce a large number of promising lines that are not only rich in pro-vitamin A but are also resistant to most maize diseases. More than 300 of these lines have been assayed at Iowa State University and at IITA-Ibadan for pro-vitamin A carotenoids.

These adapted maize inbred lines have higher concentrations of pro-vitamin A ranging from 2.5 µg/g to 10.5 µg/g. From 2004, through extensive selection, we have been able to boost the pro-vitamin A content of our maize inbred lines by 1.8 µg/g per year.

We identified and used the best inbred lines to further develop hybrids, some of which showed 25% to 79% more pro-vitamin A content than Oba Super II, a commercial yellow hybrid in Nigeria. The best hybrids were also found to have grain yields and agronomic traits comparable to those of Oba Super II.

Our studies highlight the possibility of enhancing the pro-vitamin A content of tropical maize without adversely affecting its productivity and adaptation to production environments. Future work could be undertaken to intercross these improved maize cultivars to generate lines with even higher levels of pro-vitamin A and adapted to the savannas of West and Central Africa.