A
Bridge to
Biofortified
Wheat
Filling empty stomachs, the priority when people are starving, is not enough in the long term: people need food with the nutrients they require to lead healthy and productive lives.
An estimated 3 billion people in the world who do not go hungry nonetheless suffer the debilitating effects of unhealthy diets. People who eat mostly cereal-based foods can lack such essential nutrients as iron, zinc, and vitamin A. Some developing countries overcome this deficiency by distributing supplements to the population and/or fortifying food with nutrients. Some of these programs have been successful, but they are expensive.
Biofortified Crops
An excellent means of complementing these programs would be to breed crop varieties with increased levels of minerals and vitamins. Biofortified crops could benefit malnourished populations cheaply and sustainably.
Creating biofortified versions of the main food crops is the idea behind the CGIAR Biofortification Project* funded by Danish International Development Assistance (Danida) and coordinated by the International Food Policy Research Institute (IFPRI) and the International Center for Tropical Agriculture (CIAT), which is also working on raising the micronutrient content in beans and cassava. CIMMYT is working on generating nutrient-enriched maize and wheat. Other CGIAR centers, such as the International Rice Research Institute (IRRI) and the International Potato Center (CIP), are working on their respective crops.
The project relies on the collaboration of the University of Adelaide in Australia and Cornell University in the USA, whose laboratories are testing for micronutrient and vitamin A content and micronutrient bioavailability (i.e., whether nutrients can be assimilated by humans and animals).
A Bridge to High-Nutrient Genes
Since most improved bread and durum wheat varieties lack high concentrations of iron and zinc in the grain, the search is on for good sources of the genes that control these traits. CIMMYT scientists headed by Ivan Ortiz-Monasterio have been screening materials stored in the CIMMYT genebank for five years now. They have found that wheat's wild relatives carry the highest levels of iron and zinc in the grain. Although grain nutrient levels vary depending on where plants are grown, trials in northwestern Mexico revealed that, compared to an average wheat, some of the best wild relatives had 1.8 times more zinc and 1.5 times more iron in the grain.
How to tap into genes contained in these wild species? The Wheat Wide Crosses Unit has already provided the means: bridge wheats. These wheats act as a "bridge" for transferring favorable genes from wild species to improved bread wheat. In this case, they are generated by crossing a durum wheat with a related wild grass. That is a reproduction of the chance crossing that occurred in nature between those two species and first gave rise to bread wheat about 8,000 years ago.
Bridge wheats (also called synthetic wheats) are true bread wheats and can be crossed readily with high-yielding varieties. Crossing bridge wheats with improved wheat is important because it helps to eliminate negative characteristics. The resulting wheats will be like their improved parents, except for the desired trait from the wild parent (in this case, high iron or zinc content in the grain).
Bread wheat breeders Maarten van Ginkel and Richard Trethowan use bridge wheats as a source of the high iron and zinc traits in their crosses with high-yielding lines. Since the inheritance of high levels of the two micronutrients seems to be linked, breeders can use the same bridge wheats for both traits. The researchers have advanced to the third and fourth generations, which means they are making good progress.
Work on improving the vitamin A content of wheat is just beginning. The materials in the CIMMYT wheat genebank are currently being classified for orange pigmentation, which may indicate high levels of beta-carotene, the precusor of vitamin A.
* Initially reported as the CGIAR Micronutrients Project in our Annual Report, CIMMYT in 1999-2000.
For more information:
I. Ortiz-Monasterio
(i.ortiz-monasterio@cgiar.org)
August, 2004