How might plant biologists improve the cassava plant for human use?

Many people depend on cassava roots for food. Unfortunately, the roots must undergo processing to remove sources of toxic cyanide before they are eaten. As you saw in Investigating Life: Understanding the Synthesis and Transport of Cyanogenic Glycosides, cyanide-forming molecules are formed in leaves and then transported to the roots through the vascular system. Molecular biologists have described the details of organ-specific synthesis of the machinery responsible for a major cyanogenic molecule. RNA interference (see Key Concept 18.4) has been used to block cassava leaves from making the toxic precursor, and as a result its concentration in the edible roots goes down by 99 percent compared with untreated plants. This is a promising way to reduce the requirements for processing of the crop.

Future directions

An international group of plant biologists and agricultural scientists has been set up to stimulate research on cassava. The BioCassava Plus Consortium has not only found ways to improve the nutritional quality of cassava, but has also sought ways to improve the plant’s ability to grow in drought conditions. Cassava has been crossed with a treelike relative, Manihot glaziovii, and the resulting plants produce roots that are not only fleshy and edible but that grow deep into the soil, where they can tap into water supplies far below the surface in dry climates. The hope is that this new crop variant will improve conditions for people in drought-prone places such as sub-Saharan Africa, where tens of millions of people routinely experience famine.