The plant grows as a bush or little tree and is harvested for its tubers, which are grated and pounded into a spread or flour. Currently, the African crop is threatened by African cassava mosaic virus, which can reduce yields by 75 percent. Over the past decade, the virus has caused famines in several local regions of central Africa. The disease is prevalent because the African cassava varieties, having been introduced, have no natural defense against the virus. It is best to think of cassava as tapioca pudding because it's hard to crave the food once one knows how most consumers prepare it.
All cassava contains varying amounts of cyanide, a toxin that protects the plant from insects.
Schaal said the diversity of the plant is remarkable. There must be thousands of different varieties. In Brazil, every little village has its own varieties. There are bitter ones, sweet ones, even ones used as baby food. She said the results of the work will be of use immediately.