By Tony Trewavas and Keith Dawson
The sweet potato, often called a yam, is a familiar vegetable on our supermarket shelves. It is a swollen root and its orange flesh is rich in the precursor of vitamin A. It provides nourishment equivalent to the potato (although unrelated) but will grow in poor as well as soil-rich circumstances. It has been available for some 20 years and freely sold. If you have eaten sweet potato in the last 20 years you have eaten your first GM meal.