Progress and Future Challenges to Biofortifying Staple Food Crops with Iron and Zinc.

Iron (Fe) and zinc (Zn) biofortification of staple food crops such as wheat, rice, pearl millet and beans has become a high priority for a number of plant breeding groups around the world. Within coming years, new varieties carrying the nutrient-dense traits will be released and this success is due in part to a comprehensive, across discipline collaboration where soil scientists, plant scientists, nutritionists and plant breeders have come together with a common purpose of successfully developing biofortified crops. Examples of this across discipline collaboration will be highlighted and includes the development of effective tools for assessing the genetic variation of the traits of interest. Ideally, these technologies should be relatively low in cost and also rapid in their analysis to allow for high throughput. For HarvestPlus, analysis started with the more conventional, higher costing ICP-OES analysis but has evolved to using high through-put XRF technology and many CGIAR centres are now set up with this analytical capability. The move to this technology has also allowed for high throughput screening of mapping populations to identify genetic markers associated with high Zn in wheat and results are discussed with particular reference to the effect of the environment on QTL expression. A major gap still exists in our knowledge of these environmental effects and how they impact on grain nutrient concentration. This research is of paramount importance and soil and plant scientists must play a key role in unravelling these effects. Barriers to long distance transport within the plant also require more research with a greater understanding of source-sink relationships a key research issue needing attention. Understanding the limiting steps in loading more micronutrients into the grain will allow for further genetic manipulation and result in enhanced levels of micronutrients in the seed.