Can GM crops feed the hungry?

But many people believe resistance will eventually wane.

Robert Ziegler, director-general of IRRI, says it's unlikely that those opposing GM will be able to hold back the technology forever.

"In general the issue in many developing countries is that they don't have a regulatory framework to handle them [GM crops]," Ziegler told a meeting of the American Association for the Advancement of Science (AAAS) in Chicago last year (2009).

"There are pretty strong, mostly Europe-based, lobbies who oppose their use in Sub-Saharan Africa. I think that as crops that have direct benefit to consumers come on board they will eventually be accepted."

Even Golden Rice is making some progress, he said. It is being field tested in the Philippines and the first batches may be commercially available by 2011-12.

A balanced diet

But even if opposition evaporates, there are other reasons why GM crops may fail to solve the problem of malnutrition - will tackling one particular nutritional deficiency ever bring broad success in a war that concerns so many nutrients?

For Doug Gurian-Sherman, a senior scientist in the Food and Environment Program at the US-based Union of Concerned Scientists, introducing genetically-engineered crops into a developing world environment is a piecemeal approach.

"Nutritional deficiency in an impoverished community would be better addressed by encouraging and helping people eat a balanced diet that includes green leafy vegetables and protein rather than trying to pack everything into cassava or rice," he says.

People with one deficiency often also have other nutrient deficiencies that will not be addressed by this kind of single-nutrient approach, he argues.

"I am not opposed to Golden Rice, if it works and is shown to be safe. But is it really a good use of development resources?"

Using GM to tackling a range of deficiencies in one go is the goal of the BioCassava Plus project, which aims to pack almost a full meal into cassava, a staple for 250 million people in Sub-Saharan Africa.

Turning cassava into a square meal

The GM cassava is engineered to be more nutritious on several counts and to have a longer shelf life, disease resistance and lower cyanide levels. Early versions of the plant, with one or two characteristics introduced, are undergoing field trials in Nigeria and Puerto Rico, and is set to be tested in Kenya.