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The Color Orange: Key to More Nutritious Maize?

May 14, 2012
CIMMYT E-News, vol 2 no. 10, October 2005

colorOrangeThe HarvestPlus Maize group examines progress toward breeding maize with enhanced pro-vitamins A, iron, and zinc.

CIMMYT maize scientists and colleagues from national programs in the key countries targeted by HarvestPlus reported significant progress in identifying maize with elevated concentrations of iron, zinc, and pro-vitamins A (chemicals the human body can convert to vitamin A) in their elite maize varieties and germplasm collections. The results of two years of work were presented at the second HarvestPlus Maize meeting hosted by EMBRAPA, the national agricultural research program of Brazil at their maize and sorghum research station in Sete Lagoas.

Maize is a key target crop for nutritional enhancement because it is so widely consumed in areas where high malnutrition—especially vitamin-A deficiency—exists. Scientists working in the HarvestPlus program hope eventually to breed high-quality, high-yielding maize with enhanced pro-vitamins A, iron, and zinc content. These micronutrients in maize will have to be in a form that survives processing and can be utilized by the human body.

The first planning meeting for the maize scientists was held in 2003 in Ethiopia. “We’ve come a long way since we first met two years ago,” says Kevin Pixley, the HarvestPlus Maize coordinator and Director of CIMMYT’s Tropical Ecosystems Program. “But we have also realized that this is a very complex subject with many assumptions that have to be validated.”

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CIMMYT maize breeder Dave Beck showed the group results of screening of CIMMYT elite highland and transition zone maize germplasm for enhanced levels of pro-vitamins A, zinc, and iron. HarvestPlus nutritionists have set minimum targets for the concentrations of these micronutrients in maize. The good news is that for zinc, CIMMYT has identified material that was already above the threshold. For iron the picture is less promising as existing lines identified have only 60 percent of the required minimum level for iron. For pro-vitamins A CIMMYT has examined hundreds of lines. The best CIMMYT lines have about 75 percent of the minimum requirement, but sources identified by project partners in the USA have the minimum required level of pro-vitamins A. The CIMMYT team is now breeding to enhance pro-vitamins A concentration for highland, transition zone, mid-altitude, and lowland-adapted materials.

A topic of keen interest at the meeting was how to convince people to adopt any nutritionally enhanced maize varieties that might be developed. In much of eastern and southern Africa, white maize is preferred over yellow maize. Scientists in Zambia and Zimbabwe had conducted studies about the acceptability of yellow maize. Both studies found that yellow maize is associated with food aid and that was one reason people did not want to eat it. Scientists know there is a strong correlation between the color of the maize and the total level of carotenoids. Some of these carotenoids are precursors for vitamin A “pro-vitamins A.” Torbert Rocheford, a professor of plant genetics at the University of Illinois, suggested that the debate should not actually be about yellow maize in many parts of Africa. He said what we should be talking about is orange maize—something new that will not carry the stigma of yellow maize but will have high pro-vitamins A content.

For further information, contact Kevin Pixley (k.pixley@cgiar.org).