CBN-V Video Archives - PS1-02
Cyanogenesis, Bad or Good?

Rosling H.

Division of International Health, Dept of Public Health, Karolinska Institutet, Se 171 76 Stockholm, Sweden hans.rosling@phs.ki.se

Cassava is a major staple food and yet most roots contains high levels of the potentially toxic cyanogenic glucoside linamarin. Depending on our disciplinary background this evokes two different thoughts. The first is the imperative: "Lets get rid of cyanogenesis!" This thought made food scientists show that processing removes cyanogens and it made molecular geneticist develop acyanogenic transgenics. The second thought is the question: "Why have farmers maintained a toxic food crop for thousands of years?" Anthropological inquiry into female small-scale farmers perceptions reveals that cyanogenisis protects cassava from thievery, vermin and unplanned harvest by family members. SSR markers used as gold standard shows that farmers can keep many cultivars apart, especially those with high and low glucoside levels. By tasting root tips for bitterness they predict toxicity of each root and as processing is needed to provide the type of food they want, reduction of cyanogens comes as an extra benefit. Why then have other staples crops been selected to exclude toxic varieties? Consider that the cassava root, in contrast to all other major providers of human dietary starch, is a non-reproductive plant organ. This explains the need for cassava cyanogenesis and several other characteristics of cassava.

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