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Colocasia esculenta
Colocasia esculenta (L.) Schott, (Colocasia antiquorum Schott), Araceae, known as colocasia or taro, is believed to have originated in eastern India, and has been in cultivation in tropical and subtropical Asia for over 10,000 years, preceding rice. It requires high soil moisture content, and thrives under warm, humid and waterlogged conditions. It is now cultivated in most tropical parts of the world.
The tuberous rhizomes (underground stems) called corms (with smaller ‘branches’, cormelets) (Colocasia esculenta2, Colocasia esculenta3), are an important source of edible staple starch, same as that of potato, sweet potato and tapioca. The flour is used in soups, gruels, gravies and puddings. Taro-lactin and taro-malt are good infant foods. Taro starch is also used in the production of industrial alcohol.
The corms are used as a vegetable, cooked or fried, like potato. The leaves (Colocasia esculenta1), are consumed in different ways, like spinach. They are rich in vitamin C and a- and b-carotenoids (12 mg/ 100 g), the precursors of vitamin A.
The raw corms and leaves are acrid, but thorough cooking makes them harmless, as the offending compounds are thermolabile. Juice of the tubers contains amylase and saponin.
Juice of the petioles and leaves is an astringent, styptic and rubefacient. Juice of the corms is used in alopecia and scorpion sting.
There is an enormous variability in the yield, size and number of the tubers per plant depending upon environmental and genetic factors. The tubers shown in Colocasia esculenta2 are a sample from plants growing in a rather drier soil, while those in Colocasia esculenta3 are a sample from plants growing along canal bunds. There is a compelling need for a systematic study of the extensive genetic variability, not only in India, but even outside, to help the identification of genetic varieties and land races and selection of superior varieties. A long time ago Alexander van Humboldt (1807) made such a suggestion, but still colocasia awaits the serious attention of the taxonomist, the agricultural geneticist and the plant breeder.
Tannia (Xanthosoma sagittifolium, Araceae) a new world species, is as important as colocasia, in the tropical Americas and Africa. Hybridising taro and tannia is expected to produce a crop superior to both. Both the crops rarely flower under cultivation. This does not affect the cultivator, as they are vegetatively propagated from the corms, but frustrates the plant breeder. Protoplast culture and somatic hybridisation are considered as the only option, but no serious attempts have been made so far.