logo of PROTA Prota 2: Vegetables/Légumes
Record display


Colocasia esculenta (L.) Schott

Protologue
Schott & Endl., Melet. bot.: 18 (1832).
Family
Araceae
Chromosome number
2n = 28, 42
Synonyms
Colocasia antiquorum Schott (1832).
Vernacular names
Taro, dasheen, eddoe, cocoyam, elephant ear (En). Taro, songe, madère, chou -chine, dachine (Fr). Colcas, alcolcas, inhame da Africa, inhame do Egipto (Po). Mjembe, mjimbi, myugwa (Sw).
Origin and geographic distribution
Colocasia esculenta occurs wild in tropical Asia extending as far east as New Guinea and possibly northern Australia. A type with long stolons occurring throughout this region has been postulated as the ancestor of cultivated taro on the basis of ribosome-DNA analysis. Taro is believed to have been domesticated in northern India, but independent domestication in New Guinea has also been suggested. Domestication is believed to have taken place at a very early date, even before the domestication of rice. It was spread by human settlers eastward to New Guinea and the Pacific over 2000 years ago, where it became one of the most important food plants economically and culturally. Distribution to China and via Arabia to Egypt and East Africa also occurred at least 2000 years ago. From there taro was taken by Arab people to West Africa. It was introduced into Europe from Egypt. From Spain it was taken to the New World and new introductions may have been made into West Africa from tropical America. Eddoe types (having a central corm and many large cormels) may have originated in China, from where they spread to the Caribbean region, and from there to Africa. Presently taro is grown in many parts of the tropics and subtropics, as a tuber crop and leafy vegetable. In Africa, the importance of taro as staple food has been eroded by tannia (Xanthosoma sagittifolium (L.) Schott) as the latter makes a better fufu. In Africa consumers consider taro as a staple crop of lower value than yam, sweet potato or cassava. In many regions it is naturalized.
Uses
The soft white-fleshed corms of taro are eaten boiled, fried or roasted as a side dish or are used for making fufu. They are popular as they quickly satisfy hunger, even when only a small amount is eaten. In cultivars with a single large main corm (dasheen type) the product is comparatively mealy, whereas in eddoe types the cormels have a more firm structure and taste somewhat nutty. The corm is also sliced and fried into taro chips and is used in the preparation of soups, beverages and puddings. It is well tolerated in the diet of allergic children and adults with gastro-intestinal disorders. It is said to reduce dental decay in children. The starch is used in baby foods and as cereal substitute. In Hawaii the corms are processed into flour, used for biscuits and bread; all over the Pacific Islands, they are also boiled and made into a paste that is left to ferment to produce ‘poi’. The Chinese feed peelings and leaves and corms from wild types and inferior cultivars to pigs.
Taro leaves and leaf stalks are used as a leafy vegetable and potherb for soups and sauces, or as relish. They are especially popular in parts of West Africa, north-eastern India and the Caribbean region. The leaves and leaf stalks contain an irritant substance, which causes scratchiness in the mouth and throat, but cooking resolves this. Leaves and leaf stalks of the dasheen type seem to be less acrid than those of the eddoe type. The stolons that are formed in some types are eaten too.
Medicinal uses of taro are few. In Gabon raspings from the corm are applied as a poultice to maturate boils, and to treat snakebites and rheumatism. In Mauritius boiled young leaves are eaten to treat arterial hypertension and liver affections, whereas juice is applied externally to treat eczema. In Madagascar the corms are used to treat boils and ulcers. In Gabon the leaves in combination with leaves of Tephrosia sp. are reportedly used in fish poison. Fibre obtained from the leaf stalk has been used for plaiting.
Production and international trade
Few sources report the productions of taro and tannia (Xanthosoma sagittifolium) separately. World production of taro and tannia corms in 2002 as given by FAO was 9.4 million t from 1.6 million ha; of this amount 7 million t were produced from 1.4 million ha in Africa. Nigeria (3.5 million t) and Ghana (1.8 million t) are the leading producers, followed by China (1.6 million t). An estimate of the annual world production of taro corms indicates about 5.6 million t, with a little more than half of this amount produced in Africa, and 1.6 million t in Nigeria and 0.5 million t in Ghana. Taro corms and leaves, although common in local markets, are mostly grown for subsistence and home consumption. Large-scale commercial production is not common. Local consumption forms the greatest part of taro produced in other continents too. However, small amounts are imported in Europe and Australia for the immigrant community, and also Trinidad and Tobago import some taro.
Properties
The nutritional composition of taro corms per 100 g edible portion (66% of product as harvested) is: water 68.3 g, energy 444 kJ (106 kcal), protein 1.4 g, fat 0.2 g, carbohydrate 26.2 g, dietary fibre 3.5 g, Ca 25 mg, Mg 33 mg, P 58 mg, Fe 0.8 mg, carotene 37 μg, thiamin 0.08 mg, riboflavin 0.03 mg, niacin 0.7 mg, ascorbic acid 13 mg. Fresh taro leaves contain per 100 g edible portion (70% of product as harvested): water 85.7 g, energy 147 kJ (35 kcal), protein 4.4 g, fat 0.9 g, carbohydrate 2.6 g, dietary fibre 4.0 g, Ca 110 mg, Mg 45 mg, P 60 mg, Fe 2.3 mg, carotene 6980 μg, thiamin 0.2 mg, riboflavin 0.45 mg, niacin 1.5 mg, folate 39 μg, ascorbic acid 52 mg (Holland, B., Unwin, I.D. & Buss, D.H., 1991).
The itchiness in the mouth and throat that is caused by the fresh uncooked leaves and corm is a result of cells containing raphids (bundles of calcium oxalate crystals) that disappear with cooking. Taro contains enzyme inhibitors, particularly with inhibitory activity against trypsin and chymotrypsin, but these are largely destroyed during cooking. The starch particles are small, 1–6.5 μm in diameter. The corms of some cultivars contain mucilage composed of l-arabinose and d-galactose.
Adulterations and substitutes
Leaves and corms of taro can be replaced by leaves and corms of tannia (Xanthosoma sagittifolium).
Description
Erect perennial herb up to 2 m tall, but mostly grown as an annual; root sytem adventitious, fibrous and shallow; storage stem (corm) massive (up to 4 kg), cylindrical or spherical, up to 30 cm × 15 cm, marked by a number of rings, usually brown, with lateral buds giving rise to cormels, suckers or stolons. Leaves arranged spirally but in a rosette, simple, peltate; petiole up to 1 m long, with distinct sheath; blade cordate, up to 85 cm × 60 cm, with rounded lobes at base, entire, thick, glabrous, with 3 main veins. Inflorescence a spadix tipped by a sterile appendage, surrounded by a spathe and supported by a peduncle much shorter than petiole. Flowers unisexual, small, without perianth; male flowers in upper part of spadix, with stamens entirely fused; female flowers at base of spadix, with superior, 1-celled ovary having an almost sessile stigma; male and female flowers separated by a band of sterile flowers. Fruit a many-seeded berry, densely packed and forming a fruiting head. Seeds ovoid to ellipsoid, less than 2 mm long, with copious endosperm.
Other botanical information
Colocasia comprises 8 species from tropical Asia, and is classified in the tribe Colocasieae, together with e.g. Alocasia. There are 2 cultivar-groups of taro: Dasheen Group with a single large corm producing few small cormels, usually diploid (2n = 28); and Eddoe Group (frequently classified as var. antiquorum (Schott) F.T.Hubb. & Rehder) producing many large cormels, which are the main product, and usually triploid (2n = 42). Most taro cultivars in Africa belong to Eddoe Group.
Taro is sometimes confused with tannia (Xanthosoma sagittifolium) because of its similar appearance. A ready distinction lies in the junction of the leaf stalk with the blade: in taro the leaf is peltate, in Xanthosoma not.
Growth and development
Planting is done usually in the beginning of the rainy season. After planting, growth of new roots and leaves starts after 2 weeks, the growth of suckers after 2 months. Growth of the corms also starts after about 2 months, in flooded taro after 3–5 months. There is a continuous turnover of leaves. After 4–5 months leaf area and mass reach their maximum, thereafter leaf stalks become shorter and leaf blades smaller and fewer. Most clones rarely flower and many do not flower at all. However, flowering can be induced by treatment with gibberellic acid. Picking of the leaves may start when the plants have about 6 leaves 3 months after planting. Intensive leaf harvesting may reduce corm size and yield, and number of suckers. Corms are ready for harvesting 8–10 months after planting for rainfed taro, and 9–12 months for wetland taro, although the corms reach their maximum weight a few months later.
Ecology
Taro does best in tropical lowland in areas where annual rainfall exceeds 2000 mm. It is well adapted to high temperatures and relative humidity. Most types respond well to fairly stable temperature regimes of 21–27°C. Taro is rather tolerant to shade and for that reason suitable as intercrop under coconut, cocoa or coffee. Eddoe types are more resistant to drought and low temperatures than dasheen types, and the former are grown successfully as far north as Korea and Japan. Taro can withstand highly reduced soil conditions. It is mainly found in marshy areas and on river banks in savanna areas. It can be grown under dryland and flooded conditions, each requiring adapted cultivars. Cultivars adapted to wet soil conditions withstand flooding without damage provided the water is not stagnant. Flooded cultivation is more intensive and requires greater attention than dryland cultivation. Under flooded conditions, the water level should not rise to a depth of more than 5–8 cm; with this method it takes longer to mature in comparison to dryland taro, but yields are higher. Eddoe types prefer well-drained loamy soils, and dasheen types grow best where the soil is heavy and has high moisture-holding capacity. A pH of 5.5–6.5 is optimal. Some cultivars tolerate high soil salinity.
Management
In tropical Africa upland taro is often intercropped with other vegetables. In Ghana farmers normally intercrop taro with sugar cane and at times with maize before complete flooding of the field. In Hawaii taro is grown continuously for several years in flooded fields. After a few years the fields are dried and planted with tomato, cucumber or capsicum pepper before the field is returned again to flooded taro. In South-East Asia, upland taro is often grown on dykes of paddy fields.
Taro requires good soil fertility and adequate organic matter. Flooded taro requires greater quantities of fertilizer for maximum yields than upland taro. Potash is particularly important and the crop also has a relatively high calcium requirement. General recommendation for taro is 40–80 kg/ha N, 15–30 kg/ha P and 50–100 kg/ha K. Some farmers in Ghana use organic manure (mainly from poultry) resulting in appreciable yields. Since the crop grows best in conditions where water is non-limiting, water management is a key factor. In situations with abundant water availability, closer spacing is advised; also when taro is intercropped it can be planted closer. Weeding is necessary until the canopy closes; in flooded cultivation growth of weeds is limited, and they can be easily controlled mechanically.
Propagation and planting
Taro is propagated vegetatively. It is sometimes difficult to keep planting material in a healthy condition during the dry season or periods of drought. Essentially 4 types of planting material are used: side suckers growing from the main corm, small unmarketable cormels (60–150 g), corm pieces, and setts or ‘huli’, i.e. the apical 1–2 cm of the main corm with 15–20 cm of the leaf stalks attached. In Ghana planting is mainly by use of either young suckers or mature setts cut from harvested corms. Planting material must be taken from healthy plants. Cormels are planted at a depth of 5–7.5 cm. Planting on ridges facilitates harvesting. For upland cultivation in the Philippines, furrows 30 cm deep and 80 cm apart are prepared. In flooded culture fields are ploughed, puddled and carefully levelled. Planting is done after draining the field or into 2–5 cm of standing water. The planting distance is 50–80 cm in the row and 70–120 cm between rows. For breeding purposes taro can be propagated by seed.
Diseases and pests
Taro blight (Phytophthora colocasiae) is a major wetland taro disease, causing purple to brown circular water-soaked lesions. It is the most devastating taro disease, particularly in the Pacific region, where it has caused considerable losses, e.g. in the Solomon Islands, which have resulted in the crop being partially replaced by sweet potato. This disease is partially controlled by use of copper- or phosphor-based fungicides, but spraying is tedious and costly. Increasing plant spacing or intercropping reduces losses. Resistance has been found in germplasm collections. Several species of Pythium cause taro soft rot, with wilting and chlorosis of leaves. Control is possible by use of healthy planting material, crop rotation and treating planting materials with fungicide. Sclerotium rot caused by Sclerotium rolfsii is characterized by stunting of the plant, rotting of corm and formation of many spherical sclerotia in the corm. Control is by soil drenching. In both flooded and upland taro, dark brown spots that appear in older leaves are caused by Cladosporium colocasicola and Phyllosticta colocasiae. Dasheen mosaic virus (DsMV) and other viruses have been reported but are seldom serious. In the Pacific region the alomae virus disease causes serious damage. Symptoms start with a feathery mosaic on the leaves followed by crinkling and formation of outgrowths on the surface. Finally the entire plant becomes stunted and dies. Alomae disease is caused by the combined infestation by the taro large bacilliform virus (TLBV) and the taro small bacilliform virus (TSBV). Presence of TLBV only results in a milder form of the disease called ‘bobone’. The viruses are transferred by a grasshopper and a mealy bug, respectively, but not by mechanical contact. In Hawaii, two diseases of unknown causative agents characterized by small, hardened portions in the lower third of the corm (‘hard rot’) and a soft rubbery corm which is low in starch content and exudes water when squeezed (‘lohloli’) are threatening. Attack by root-knot nematodes (Meloidogyne spp.) can result in considerable crop loss. Control is by treating planting material with water at 40°C for 50 minutes, by the use of disease-free material or by soil fumigation.
Insect pest on taro may cause serious damage. Damage by Hercothrips indicus (synonym: Heliothrips indicus) thrips is shown as a silvery discoloration of the leaves and can result in severe leaf shedding. Adults of taro beetles (Papuana spp., e.g. Papuana huebneri and Papuana woodlarkiana) tunnel in the corm up to the growing point. Young plants wilt and die but older plants usually recover. This pest is reported in the Pacific and South-East Asia, but not in Africa. It can be controlled by applying insecticide in the planting holes. Severe losses have been suffered by a number of countries growing the crop (Polynesia, Hawaii, the Caroline Islands and Samoa), as a result of leafhoppers. Biological control and insecticide dusting are effective control measures. Larvae of the sweet potato hawk moth (Agrius convolvuli) defoliating the plant reduce corm quality.
Harvesting
The harvest of the leaves may start 2 months after planting. Unfolding or young expanded leaves are preferred. From then on, continuous harvesting is assured provided sufficient water is available. Harvesting immature corms may start from 5 months onwards. Maturity of the crop depends on the cultivar and method of cultivation (upland or flooded). Dasheen types take about 8–10 months to mature while eddoe types mature in 5–7 months. Irrigated taro matures a few months later. Dasheen types may be ratooned, lifting the main tuber and leaving the small ones for successive harvests. Maturity indicators are yellowing of the leaves and a slight lifting of tubers. Commercial growers in Ghana allow the crop to remain over one year when prices are not favourable.
Yield
The yield of leaves is not recorded. Corm yields are very variable. The average yield on a world basis is 5–6 t/ha, but a good crop on fertile soil gives at least 12 t/ha and yields higher than 40 t/ha have been achieved in Hawaii.
Handling after harvest
Leaves can only be stored for a few days. Corms can be stored under ambient condition for up to 6 weeks, provided they have not been bruised during harvesting. However, they often keep well for only 2 weeks. Corms of dasheen types can be stored at 10°C for up to 6 months. To avoid post-harvest problems, harvesting is best done when the corms are dry. For the fresh market, the corms are usually washed and the roots and fibres are discarded. In Ghana, the entire top parts are removed, whereas in Asia 30–45 cm of the leaf stalks are usually left attached. Pieces of the corm may be dried and stored as chips.
Storing planting material at about 2°C results in a delay of growth of 40–60 days; storage at 11–13°C and a relative humidity of 85–90% improves later growth. Corms for planting are normally left in the ground and are harvested when needed.
Genetic resources
Genetic variability in taro is large in South-East Asia and New Guinea, but small in Africa and the Pacific region. Farmers in West Africa and elsewhere grow many clones. Loss of genetic diversity is minimal. Germplasm collections are maintained in several institutes in Asia and the Pacific region. The largest collection is held at the Bubia Agricultural Research Station, Bubia, Papua New Guinea.
Breeding
The discovery of methods of flower induction in taro greatly facilitates breeding. Breeding programmes focus on resistance to diseases and pests, especially taro blight and taro beetles. Little research work has been done on breeding in Africa. In Nigeria techniques for promoting flowering and seed production using hand pollination have been successful. Tissue culture techniques for vegetative propagation have been developed in Hawaii and offer hope for obtaining virus-free planting material and for rapid multiplication of selected plants.
Prospects
Taro is a vegetable with great potential. The importance of the leaves as leafy vegetable and the corms as relish is increasing. However, the importance of the corms as starchy staple food is declining since they are considered inferior to other roots and tubers. Taro is an excellent multipurpose food crop for subsistence agriculture and home gardens, giving food security. Its ability to grow under flooded conditions and to tolerate salinity makes it suitable for localities where few other crops grow. As such it merits more attention in research and breeding, focusing on disease resistances, yield and quality. For commercial production, separate cultivars need to be developed for harvesting leaves or corms.
Major references
• Abbiw, D.K., 1990. Useful plants of Ghana: West African uses of wild and cultivated plants. Intermediate Technology Publications, London and Royal Botanic Gardens, Kew, United Kingdom. xii + 337 pp.
• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, United Kingdom. 960 pp.
• Ivancic, A. & Lebot, V., 2000. The genetics and breeding of taro. Librairie du CIRAD, Montpellier, France. 194 pp.
• Matsuda, M. & Nawata, E., 2002. Geographical distribution of ribosomal DNA variation in taro, Colocasia esculenta (L.) Schott, in eastern Asia. Euphytica 128: 165–172.
• Onwueme, I.C., 1978. The tropical tuber crops. Yams, cassava, sweet potato, cocoyams. John Wiley & Sons, Chichester, United Kingdom. 234 pp.
• Plucknett, D.L., de la Peña, R.S. & Obrero, F., 1970. Taro (Colocasia esculenta). Field Crops Abstracts 23: 413–423.
• Purseglove, J.W., 1972. Tropical crops. Monocotyledons. Volume 1. Longman, London, United Kingdom. 334 pp.
• Rosna Mat Taha, 2003. Colocasia esculenta (L.) Schott. In: Lemmens, R.H.M.J. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(3). Medicinal and poisonous plants 3. Backhuys Publishers, Leiden, Netherlands. pp. 130–131.
• Tindall, H.D., 1983. Vegetables in the tropics. Macmillan Press, London, United Kingdom. 533 pp.
• Wilson, J.E. & Siemonsma, J.S., 1996. Colocasia esculenta (L.) Schott. In: Flach, M. & Rumawas, F (Editors). Plant Resources of South-East Asia No 9. Plants yielding non-seed carbohydrates. Backhuys Publishers, Leiden, Netherlands. pp. 69–72.
Other references
• Barrau, J., 1957. Les Araceae à tubercules alimentaries des Iles du Pacifique Sud. Journal d’Agriculture Tropicale et de Botanique Appliquée 4: 34–52.
• Barrau, J., 1959. Fruits et graines du taro (Colocasia esculenta (Linn.) Schott). Journal d’Agriculture Tropicale et de Botanique Appliquée 6: 436–438.
• Coursey, D.G., 1968. The edible aroids. World Crops 20: 25–30.
• Ezumah, H.C. & Plucknett, D.L., 1973. Response of taro (Colocasia esculenta (L.) Schott) to water management, plot preparation and population. 3rd International Symposium Trio, Root Crops, Ibadan, Nigeria.
• FAO, 1996. The state of the world’s plant genetic resources for food and agriculture. Food and Agriculture Organization, Rome, Italy. 336 pp.
• Greenwell, A.B.H., 1947. Taro: with special reference to its culture and use in Hawaii. Economic Botany 1(3): 276–289.
• Gollifer, D.E. & Brown, J.F., 1974. Phytophtora leaf blight of Colocasia esculenta in the British Solomon Islands. Papua New Guinea Agricultural Journal 25: 6–12.
• Jackson, G.V.H. & Gollifer, D.E., 1975. Disease and pest problem of taro (Colocasia esculenta (L.) Schott) in the British Solomon Islands. PANS 21(1): 45–53.
• Kochhar, S.L., 1981. Tropical crops: a textbook of economic botany. Macmillan, London, United Kingdom. 476 pp.
• Kranz, J., Schmutterer, H. & Koch, W. (Editors), 1977. Disease, pests and weeds in tropical crops. John Willey & Sons, Cichester, United Kingdom. 666 pp.
• Messiaen, C.-M., 1989. Le potager tropical. 2nd Edition. Presses Universitaires de France, Paris, France. 580 pp.
• Onwueme, I.C., 1999. Taro cultivation in Asia and the Pacific. [Internet] FAO Regional Office for Asia and the Pacific, Bangkok, Thailand. http://www.fao.org/DOCREP/005/AC450E/ac450e00.htm#Contents. Accessed June 2004.
• Oyenuga, V., 1968. Nigeria's foods and feeding stuffs. University Press, Ibadan, Nigeria. 99 pp.
• Parkison, S., 1984. The contribution of aroids in the nutrition of people in the South Pacific. In: Chandra, S. (Editor). Edible aroids. Clarendon Press, Oxford, United Kingdom. pp. 215–224.
• Plucknett, D.L. & de la Peña, R.S., 1971. Taro production in Hawaii. World crops 23(5): 244–249.
• Rodriguez, M.A., Rodriguez, N.A.A., Gutierrez, M.I., Mayor, Z.F. & Alfonso Castineiras, L.C., 2000. Morphological and isozymatic variability of taro, Colocasia esculenta (L.) Schott, germplasm in Cuba. Proceedings of the 12th Symposium of the International Society for Root Crops (ISTRC), September 10–16, 2000, Tsukuba, Japan.
• Vickery, M.L. & Vickery, B., 1979. Plant products of tropical Africa. Macmillan, London, United Kingdom. 116 pp.
• Wilson, J.E., 1984. Taro and Cocoyam; what is the ideal plant type? In: Chandra, S. (Editor). Edible aroids. Clarendron Press, Oxford, United Kingdom. pp. 157–159.
• Yayock, J.Y., Lombin, G. & Owombi, J.J., 1988. Crop science and production in warm climates. Macmillan, London, United Kingdom. 320 pp.
Sources of illustration
• Purseglove, J.W., 1972. Tropical crops. Monocotyledons. Volume 1. Longman, London, United Kingdom. 334 pp.
• Wilson, J.E. & Siemonsma, J.S., 1996. Colocasia esculenta (L.) Schott. In: Flach, M. & Rumawas, F (Editors). Plant Resources of South-East Asia No 9. Plants yielding non-seed carbohydrates. Backhuys Publishers, Leiden, Netherlands. pp. 69–72.
Author(s)
O. Safo Kantanka
Crop Science Department, Faculty of Agriculture, KNUST, Kumasi, Ghana


Editors
G.J.H. Grubben
Prins Hendriklaan 24, 1401 AT Bussum, Netherlands
O.A. Denton
National Horticultural Research Institute, P.M.B. 5432, Idi-Ishin, Ibadan, Nigeria
Associate Editors
C.-M. Messiaen
Bat. B 3, Résidence La Guirlande, 75, rue de Fontcarrade, 34070 Montpellier, France
R.R. Schippers
De Boeier 7, 3742 GD Baarn, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Illustrator
PROSEA
PROSEA Network Office, Herbarium Bogoriense, P.O. Box 234, Bogor 16122, Indonesia
Photo Editor
E. Boer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Safo Kantaka, O., 2004. Colocasia esculenta (L.) Schott In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
Distribution Map planted


1, plant habit; 2, corm of dasheen type; 3, corm and cormels of eddoe type.
Source: PROSEA



corm of dasheen-type


corms of the eddoe type


crop


lower side of leaf blade


flowering and fruiting plant