The nutritional value of maize can be further increased through two approaches: fortification and biofortification. Fortification involves adding micronutrients to foods as they are being processed to ensure that minimum dietary requirements are met. On the other hand, biofortification is an approach to increase the nutritional content of crops through conventional plant breeding or genetic engineering (i.e., transgenics). Biofortification offers a potentially renewable source of nutrients for those who do not have access to commercially fortified foods.  

Quality Protein Maize: A Biofortification Success Story

In the early 1970s, Drs. Surinder Vasal and Evangelina Villegas at the International Maize and Wheat Improvement Center (CIMMYT) in El Batán, Mexico began improving maize protein quality through the integration of chemistry and conventional plant breeding approaches. Their decades of research culminated in the development of Quality Protein Maize (QPM) — a type of maize with higher levels of lysine and tryptophan.  A diet including QPM has been shown to improve the health of undernourished children in Latin America and Africa. For their tremendous achievements, Drs. Vasal and Villegas received the 2000 World Food Prize.


Vitamin A: Sources and Deficiency

Vitamin A is essential for the normal function of the vision system and required for cellular growth and immune function. This fat-soluble vitamin can be obtained from animal products (retinoids) and fruits and vegetables (provitamin A carotenoids). Retinoids such as retinal and retinoic acid are the animal form of vitamin A and found in liver, eggs and dairy products. Out of the three provitamin A carotenoids  - alpha-carotene, beta-carotene and beta-cryptoxanthin - that are available from eating vegetables such as carrots, sweet potato, and spinach, beta-carotene has the highest vitamin A activity In the human body, retionids and provitamin A carotenoids are converted to retinol, the most useable form of vitamin A.   

In the developing world, Vitamin A Deficiency (VAD) is a major health problem for millions of people, especially women and children. VAD results in maternal mortality, reproductive disorders, impaired growth, night blindness and if not treated progresses to complete blindness. Globally, it is estimated that some 127 million preschool-age children are VAD, with nearly 4.4 million of them having visible eye damage due to this deficiency. Every year 250,000 to 500,000 preschool-age children become blind from VAD and about two-thirds of them die within months of becoming blind. To further complicate matters, people with VAD tend to subsist on staple foods that are typically low in provitamin A and have limited accessibility to foods rich in retinoids and provitamin A carotenoids. 

High Vitamin A Maize: New Tools for Biofortification

Maize is a staple crop to hundreds of millions of people living in developing countries, but only a few maize varieties have naturally high levels of provitamin A carotenoids like beta- carotene in their seed.  The Agricultural Research Service (ARS) along with colleagues at Cornell University, City University of New York, DuPont Crop Genetics Research, Boyce Thompson Institute, University of North Carolina-Wilmington, University of Illinois, and the International Maize and Wheat Improvement Center (CIMMYT) have made some discoveries that could change that. With the implementation of newly developed genetic and statistical tools, these researchers surveyed DNA sequences and beta-carotene seed content of diverse maize from around the world. They identified a natural mutant of a gene that produced a lower level of an enzyme involved in the carotenoid biosynthetic pathway and found that maize varieties with this mutation produced higher levels of beta-carotene.

Plant breeders typically use an analytical chemistry technique to quantify levels of beta-carotene in seed harvested from individual maize breeding lines. However, breeders need to screen hundreds to thousands of plants at a time to identify lines with higher beta-carotene levels and the analysis—with a cost of $50-75 per sample—becomes cost-prohibitive. Thankfully, the researchers have developed molecular markers (small segments of DNA) that tag the naturally mutated gene, which enables a cheaper and faster screening approach for large numbers of plants. Scientists working in developing countries with limited resources will be able to use these molecular markers to transfer the naturally mutated gene from high beta-carotene maize lines to locally adapted varieties. Research is continuing to identify additional genes that could further increase levels of carotenoids.

Thanks to Michael Gore for this section.
Stats on VAD are from: Mayer: Journal of AOAC International VOL. 90, NO. 5, 2007