Potato and Tuber Crops

Botany

• Yam tuber is neither a root structure nor a stem, but may have its origin as a hypocotyl structure.
• Tuber grows from a small corm structure located at base of stem. In all yams, tubers are renewed annually.
• Tubers may be single or two or three. D. esculenta produces a large number of small and spindle shaped tubers.
• Dioscorea bulbfera and D.alata produces a large number of small and spindle shaped tubers. D. bulbifera and D.alata produce aerial bulbs called bulbils from axils of leaves.
• Whole tubers or pieces of tubers with stem are used for planting in yams.
• Bulbils can also used for propagation. Stem is weak and climbs on trees by twining.
• In Dioscorea rotundata stem remains erect upto one metre height.
• Leaves are simple.
• All species are dioecious.
• Fruits are dehiscent tri-locular capsules.
• Seeds are small and dispersed by wind.
• Even though all the species have seed dormancy for three months, Dioscorea alata does not exhibit seed dormancy.
• In Dioscorea alata, majority of male clones are tetraploids (2n = 40) and majority of females have higher ploidy level (2n=60 or 80).