Yam bean ( Pachyrhizus erosus ), illustration
|Rich. ex DC.|
Although these species are closely related to a number of other crops called “ beans ”, the legumes of which are consumed, the root tubers are mainly used in the yam bean species; the seeds are poisonous, but are eaten cooked anyway. The tubers are used as food and for refreshment (water storage). The seeds , leaves and pods are more or less poisonous.
Yam beans have their natural occurrence from Mexico to South America . Three of the species are cultivated in South America, one of them, the yam bean , was transported by galleons from Mexico via the Philippines to Asia centuries ago, where it became one of the favorite plants of Chinese gardeners. Although yam beans can thrive in dry and wet, subtropical or tropical climates, they prefer hot climates with average rainfall. Yam bean plants can tolerate drought, but are sensitive to frost or waterlogging.
Yam beans are perennial herbaceous plants that climb or tend to grow rapidly and their stems can reach up to 5 meters in length. They develop many white or purple flowers. The roots are sugar-beet-shaped or more elongated and weigh up to 5 kg. They can be propagated as seeds or root cuttings.
Use and ingredients
Of the yam beans, only the root meat is edible, as all other parts of the plant (except the flower) contain more or less of the poisonous Rotenone and its glycosides . The root bark is easy to peel and reveals the juicy, sweet-tasting meat very similar to potatoes , which is usually eaten raw in salads or lightly cooked.
There are about five to six species in the genus:
- Andean tuber bean ( Pachyrhizus ahipa (Wed.) Parodi ): cultivated in northwest Argentina , Bolivia , Peru
- Yam bean ( Pachyrhizus erosus (L.) Urban , Syn .: Pachyrhizus angulatus Rich. Ex DC. , Pachyrhizus bulbosus (L.) Kurz , Dolichos erosus L. ): Mexico and Central America , cultivated and wild in the tropics of the world.
- Pachyrhizos ferrugineus (Piper) M. Sørensen : Mexico , Central America , parts of Colombia
- Pachyrhizos panamensis R. T. Clausen : Panama , parts of Colombia , Ecuador
- Tuberous bean ( Pachyrhizus tuberosus (Lam.) Spreng. , Syn .: Dolichos tuberosus Lam. , Cucara tuberosa (Lam.) Britt. ): Ecuador , cultivated all over South America .
- Joachim Alkämper: Versatile information on Art. (German)
- National Research Council (US): Tropical Legumes: Resources for the Future. (Paperback) Books for Business, 2002. ISBN 0-89499-192-2 . Pp. 21-27.
- Taxonomy at GRIN (Engl.)
- AS Zanklan: Agronomic performance and genetic diversity of the root crop yam bean (Pachyrhizus spp.) Under West African conditions. Doctoral thesis at the Georg-August-Universität Göttingen 2003. Online version (PDF; 603 kB)