Finally, they introduced a gene for a protein rich in the amino acid cysteine, which helps the gut to absorb iron, into a third set of plants. Each of the three strategies works, says Potrykus. The researchers now plan to cross these plants to combine all three traits. Rice also lacks vitamin A, leading to blindness and reduced disease resistance in about 400 million children worldwide. Working with Peter Beyer of the University of Freiburg in Germany, Potrykus and his colleagues inserted three genes that promote the production of beta-carotene, which is converted to vitamin A in the body.
Several hurdles remain before either new rice appears in farmers' fields, however.
So far, Potrykus has inserted the genes into short-grained rice because these japonica varieties are easier to modify genetically. Breeders must now cross the genes into the long-grained indicas that are the preferred rice in tropical regions, where the deficiencies are most common. That, together with field trials of the new varieties, should take about three years. Some critics of engineered, crops have given the work a cautious welcome, as it is designed to aid the developing world, rather than to boost profits of multinational companies. It looks as if a brand-new family tree, unveiled in St Louis, will overtum many old ideas about who's related to whom in the world of green plants.