Cassava roots, a major food in Africa, contain cyanogenic glucosides that may cause toxic effects. Malawian
women farmers considered fields of seemingly similar cassava plants to be mixes of both ‘cool’ and ‘bitter’
cultivars. They regard roots from ‘cool’ cultivars as non-toxic. Roots of ‘bitter’ were considered to require extensive
traditional processing done by women to be safe for consumption. But curiously, these women farmers preferred
‘bitter’ cultivars since toxicity confers protection against theft, which was a serious threat to the food security of
their families. We studied how well these farmers comprehend the effects of genetic variations in cassava when
dealing with cyanogenesis in this complex system. Using molecular markers we show that most plants farmers
identified as belonging to a particular named cultivar had a genotype typical of that cultivar. Farmers’ ethnoclassification
into ‘cool’ and ‘bitter’ cultivars corresponded to a genetic sub-division of the typical genotypes of
the most common cultivars, with four-fold higher cyanogenic glucoside levels in the bitter cultivars. Examining
morphology, farmers distinguished genotypes better than did the investigators when using a standard botanical key.
Undoubtedly, these women farmers grasp sufficiently the genetic diversity of cassava with regard to cyanogenesis
to simultaneously benefit from it and avoid its dangers. Consequently, acyanogenic cassava – the breeding of
which is an announced good of some cassava genetic improvement programmes – is not a priority to these farmers.
Advances in molecular genetics can help improve food supply in Africa by rapid micropropagation, marker assisted
breeding and introduction of transgenic varieties, but can also help to elucidate tropical small-scale farmers’ needs
and skills.