The Potato Menace

38 YEARS AGO If poorly packaged or exposed to excess sun, the humble potato can become highly toxic, causing chronic enteritis or even death.

The humble potato is a potential killer, because it contains certain alkaloids which, in their concentrated form, are deadly poisonous. Although these alkaloids do not pose any threat to human health in correctly handled potatoes, certain methods of handling and presentation for marketing can and do promote the development of these toxins.

All members of the potato family produce these alkaloids or toxins, according to Mr Theuns Duvenhage, formerly of the National Potato Work Team. Included in the potato family are tobacco, tomatoes, chillies, eggplant, gooseberries, nightshade and stinkblaar. Not only are the tubers and fruits of these plants to a greater or lesser degree poisonous, but so is the foliage.

In the fruits of these plants, toxicity usually decreases as the fruits ripen. For example, the green fruits of nightshade are extremely poisonous, but the ripe berries are edible, says Mr Duvenhage.

There are more than 10 different alkaloids present in the wild potato species. Depending on the use to which they are put as parent breeding material, for breeding resistance to disease, eelworm and insect pests, such resistant cultivars may well tend to produce alkaloids under certain conditions.

Potato breeders throughout the world are trying, through the use of repeated back crossings, to breed out those genes that are responsible for producing alkaloids, he says.