Opportunities and Strategies for Biofortified Maize

摘要

Iron, zinc and vitamin A deficiencies afflict hundreds of millions of people, particularly women and children. Because cereal grains are staple foods and provide a large portion of energy and macronutrients for most people, genetic fortification or biofortification of these cereals with vitamins and/or minerals could contribute to alleviating micronutrient malnutrition. The maize Harvest Plus project has a large number of partners working on genetic strategies to increase the provitamin A carotenoids, iron, and zinc concentrations in maize kernels, applying these strategies in breeding programs, and preparing to disseminate the resultant biofortified maize varieties in target countries. Strategies to enhance provitamin A carotenoids include selection for enzyme activity within the carotenoid synthesis pathway to increase the accumulation of β-carotene and other provitamins A. Preliminary findings suggest it may be possible to do this by selectively crossing maize lines with complementary carotenoid profiles and high carotenoid content; mapping populations are currently being evaluated in the USA and Mexico to explore the feasibility of this strategy. The natural variation in iron concentration in maize is lower than that deemed sufficient to reduce iron deficiency; therefore, efforts will be made to increase the concentration of iron in the grain through hybridization, while exploring other strategies to increase iron bioavailability by selecting for promoters of greater iron accumulation in grain, and/or low concentration of phytates that reduce the bioavailability of iron and zinc. Transgenic approaches may also be feasible, and some maize Harvest Plus partners are exploring a "golden maize" (transgenic) strategy. This paper presents an overview of strategies for maize micronutrient enhancement breeding efforts within the Harvest Plus project.