Natural Genetic Variation in Maize Nutritional Quality

They always told you to eat your carrots, to improve your eyesight. Well, a deficiency of vitamin A (found in carrots, and lots of other foods) causes eye disease in a lot of children. In areas where Maize (corn) is a significant staple, there can be a problem because maize varies a great deal in how much vitamin A it can provide via precursor molecules. A new study in Science explores this relationship.

Maize is the dominant subsistence crop in much of sub-Saharan Africa and the Americas, where between 17 and 30% of children under age of 5 are vitamin A-deficient. This results in xerophthalmia (progressive blindness), increased infant morbidity and mortality, and depressed immunological responses ... Vitamin A deficiency starts with inadequate provitamin A or vitamin A content or bioavailability in foods and is exacerbated by disease-induced malabsorption.

The study by Harjes et al ("Natural Genetic Variation in Lycopene Epsilon Cyclase Tapped for Maize Biofortification") examines the phenotypic diversity of Maize to assess the role that variation in this important crop plant contributes to the deficiencies.

It turns out

that the lycopene epsilon cyclase (lcyE) locus varies (has multiple alleles) that affect the amount of viamin A percursors that are ultimately available in the maize that is consumed.

This is probably true across many food plants for many different nutrients, and the way humans have typically avoided (though usually not intentionally) deficiencies has been to have a diverse diet. With a diverse diet what might be a deficiency in one plant ... or variety of a plant ... is compensated for by the presence of that nutrient in sufficient quantity in another food product. Also, in my view, the more meat in the diet the less likely a deciencey will emerge in a particular population, as meat tends to have the full range of nutrients (not speaking specifically of energy) since the stuff that the animal one is eating is made out of is very close to the stuff that the eater is made out of.

But in regions where meat is scarce, the staple food is based on something close to a monoculture, and the main subsistence crop can have a deficiency, then we have a problem.

It is possible that this research can lead to selection, or modification followed by selection, of varieties of maize that do not present this particular deficiency, thus solving a widespread health problem.

According to Edward S. Buckler, one of the study's authors,

By identifying these genetic variants, breeders can make varieties with higher provitamin A rapidly and inexpensively ... This research will now go into the major effort to help create maize varieties in sub-Saharan Africa for subsistence farmers ... Since maize is consumed for all three meals a day in much of Africa, maize is a good target for biofortification.

---

Harjes, Carlos E. , Torbert R. Rocheford, Ling Bai, Thomas P. Brutnell, Catherine Bermudez Kandianis, Stephen G. Sowinski, Ann E. Stapleton, Ratnakar Vallabhaneni, Mark Williams, Eleanore T. Wurtzel, Jianbing Yan, Edward S. Buckler. (2008) Natural Genetic Variation in Lycopene Epsilon Cyclase Tapped for Maize Biofortification. Science 18 January 2008. Vol. 319. no. 5861, pp. 330 - 333. DOI: 10.1126/science.1150255.

Press Release, Cornell University.