Your article Can GM crops feed the hungry? highlights the role that genetically modified (GM) cassava could play in alleviating malnutrition in Sub-Saharan Africa. But a cheaper — and possibly more effective — route lies in cultivating indigenous and wild varieties of the crop.
Many indigenous cultivars of staple crops, including cassava, are very rich in nutrients and often well-adapted to stresses such as poor soil or severe climate. Yet researchers and authorities in developing countries frequently neglect these varieties.
But there is progress. Our research program in Brazil has identified an indigenous cassava cultivar that is extremely palatable when cooked and, more importantly, contains 50 times more beta-carotene (a precursor to vitamin A )than common cassava.  Consuming just 100 grams of this variety can fulfil a person's entire daily vitamin A requirements.
This variety is now planted in most of the cassava farmland in Brazil's federal district.
Wild cassava is another source of cheap and accessible nutrients. In Brazil, for example, we crossed cassava cultivars, including wild species, to create hybrid cassava with 20 times more zinc and iron — key micronutrients — than common cassava. 
Research of this type can be very cheap — selecting indigenous cultivars and producing hybrid cassava cost us no more than a few thousand dollars compared with the high price of developing a GM crop, which can cost up to US$100 million.
GM crops are unlikely to reach the quality or adaptability of indigenous cultivars because, during their short synthetic life, they are not subject to natural selection, so may quickly break down or be ill-suited to local conditions. Cassava genetically engineered to resist mosaic disease is a case in point: despite spending more than US$20 million on developing it, no farmer is actively growing it.
More effort is needed to select, propagate and distribute nutritious indigenous and wild varieties of staple crops across the developing world.
At the same time, public awareness campaigns are needed to inform and re-educate people on the benefits of consuming and growing these crop varieties.
Indigenous cultivars are the precious heritage of native people — selected by them and improved over thousands of years. They deserve more attention from public authorities.
 Nassar, N.M.A. et al. Amarelinha do Amapá: a carotenoid-rich cassava cultivar. Genetics and Molecular Research. 8 1051-1055 (2009)
 Nassar, N.M.A. et al. Cassava, Manihot esculenta Crantz genetic resources: a case of high iron and zinc.