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Yam large, sub-aerial soft starchy, tuberous root
of any of various climbing vines of the genus Dioscorea, having
about 600 species under the family Dioscoreaceae. There are about 11-12
cultivated species in the tropical and subtropical regions. The most common
cultivated specie are D. alata, D. rotunda, D. opposita, D. cayenansis
and D. esculanta. Yam is the chief food of millions of people
in West India, South Afiica, Central Africa and tropical Asia. In Bangladesh
D. alata has the largest yield; average yield per plant is about
8 kg.; flesh is white or cream coloured and may even be pink or purple.
D. esculanta is a smaller palatable yam also cultivated in some
places. They are cultivated in April or May by cutting the tuber having
one or two young stem bud. In Bangladesh it is cultivated mainly as homestead
plant and consumed as vegetable. The wild species are not exploited for
either food or for any steroidal sapogenins related to sex hormones or
cortico-steriods. [Mostafa Kamal Pasha]
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