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Regeneration guidelines for major aroids

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The information on this page was extracted from:
Jackson G.V.H. 2008. Regeneration guidelines: major aroids. In: Dulloo M.E., Thormann I., Jorge M.A. and Hanson J., editors. Crop specific regeneration guidelines [CD-ROM]. CGIAR System-wide Genetic Resource Programme, Rome, Italy. 16 pp.

Before reading the regeneration details for this crop, read the general introduction that gives general guidelines to follow by clicking here.

Introduction

The major aroids comprise taro (Colocasia esculenta (L.) Schott), Xanthosoma species and swamp taro (Cyrtosperma merkusii (Hassk.) Schott), syn. C. chamissonis (Schott) Merr.). Taro Colocasia esculenta (L.) Schott (see photo below) is grown for its corm and leaves. It is an ancient crop from north-eastern India with multiple centres of domestication. A wild form, C. esculenta var. aquatilis Hassk., is the progenitor of the cultivars grown today, including those in the Pacific. It is an early introduction to Africa. Two botanical varieties have been recognized: var. esculenta (L.) Schott (dasheen) and var. antiquorum (Schott) Hubbard & Rehder (eddoe). Pan tropical dasheens have large central corms and suckers or stolons from which they are regenerated. Eddoes are more common at temperate latitudes and higher altitudes, with relatively small central corms and numerous cormels, but can also be propagated from suckers in tropical countries. Intermediate types also exist.
Xanthosoma (see photo below) is an important pan-tropical crop, with its centre of origin possibly in northern South America where some species were domesticated, probably from different wild forms. Xanthosoma is known to have been introduced to West Africa, Oceania and Asia. There are two main species, X. sagittifolium (L.) Schott and X. violaceum Schott, but the taxonomic position of the cultivated Xanthosoma species is unclear, and the name X. sagittifolium is often given to all cultivated forms. Xanthosoma is vegetatively propagated from corm setts, headsetts or cormels. Although flowers occur and seeds are viable, flowers are rare in most varieties and non-existent in some. In addition, seedlings may not breed true and hence are not recommended for regeneration.
Cyrtosperma merkusii (Hassk.) Schott (see photo below) is the only edible form of its genus. Unlike taro and Xanthosoma, the leaves are not eaten but they may be used as medicines and for making fine grade mats. Cyrtosperma is thought to have an Indo-Malay centre of origin, perhaps coastal New Guinea, Solomon Islands or West Melenesia. Wild-type plants are said to occur in the Solomon Islands. Cyrtosperma is vegetatively propagated from setts or suckers. Flowers and seed do occur but are not common and are not recommended for regeneration.
Genetic resources of aroids are conserved through vegetative propagation. It is good practice to establish a duplicate field collection as a back-up. Methods for cultivating and propagating aroids are not well documented but extensive local knowledge exists so consulting local practitioners for guidance is recommended when regenerating aroids.

Taro (Colocasia esculenta) growing in Thailand.
(photo: Grahame Jackson)

Swamp taro (Cyrtosperma merkusii) in Kiribati.
(photo: Grahame Jackson)

Xanthosoma sp. in Tonga.
(photo: Grahame Jackson)

Choice of environment and planting season

Climatic conditions

All three crops require moist soils and none of them tolerate drought.

Taro needs reliable rainfall throughout the growing season or irrigation, moist soils and maximum temperatures of around 25°C.

Xanthosoma grows in lowland and upland situations, with well-distributed rainfall, 1500–2000 mm annually, a mean temperature above 20°C, and freely draining soils of pH 5.5–6.5.
It tolerates light shade but grows well in the open.

Cyrtosperma is generally a hardy species. It tolerates shade and wind but whether it is salt tolerant, as often stated, is less certain.

Planting season

Taro

Xanthosoma

Cyrtosperma

Preparation for regeneration

Preparing planting material of taro (Colocasia esculenta) by removing any remaining roots, Tonga. (photo: Grahame Jackson)

When to regenerate

Taro

Xanthosoma

Cyrtosperma

Taro headsets ready for planting on Efate, Vanuatu. (photo: Vincent Lebot/CIRAD)

Preparation of planting material

Choose healthy planting material. Inspect corms, cormels and headsetts for rots (cause by fungi and/or nematodes) and if found remove with a clean knife or discard the material.
Remove any remaining roots (see photo of preparing planting material). Leave the prepared planting material in a well-ventilated shady place (26–30°C and 90–95% RH) for 3–5 days before planting to allow wounds on the cut surface to heal. Dust corm setts in a fungicide or ash, especially if root rot is known to be a problem in the locality.

Taro

Setts and suckers

Young taro seedling ready to be transplanted into the field, Efate, Vanuatu. (photo: Vincent Lebot/CIRAD)

Cormels

Xanthosoma

Cyrtosperma

Field selection and preparation

Taro

Xanthosoma

Cyrtosperma

Method of regeneration

Aroids are regenerated using vegetative propagation. Even within clonally propagated species, there may be some level of heterozygosity and it is recommended to plant 5 to 10 plants per accession to maintain the genetic diversity.
Taro varieties differ greatly in their time to maturity. For ease of maintenance and replanting, divide the collection into short-, medium- and long-duration accessions and plant accordingly for ease of management.

Planting layout, density and distance

A number of factors will affect spacing, making it difficult to recommend an optimum spacing or plant density. Plant collections according to the local practice.

Taro

Xanthosoma

Cyrtosperma

Planting method

Label each accession with the name, accession number and date planted. Draw a map of the collection immediately after planting. Plant at least 5, preferably 10, plants of each accession in a row. It is best to use long lasting labels (e.g. metal labels and indelible ink).

Taro

Transplanting taro seedlings into the field, Efate, Vanuatu.
(photo: Vincent Lebot/CIRAD)

Xanthosoma

Mulching of Cyrtosperma with organic material using local practices, Tarawa, Kiribati. (photo: Grahame Jackson)

Cyrtosperma

Pits

Swamps

Crop management

Irrigation

Taro and Xanthosoma

Soil needs to be moist at planting. If irrigation is not available, it is important to plant the collection at the beginning of the wet season. If harvesting and replanting can be matched with seasonal rains, irrigation can be minimized.

Cyrtosperma

Irrigation is not necessary as collections are planted in pits near the water-table or in swamps. Choose sites where local knowledge suggests that droughts will have minimal impact and, if possible, duplicate collections in the field.

Fertilization

Perform soil analysis to determine the amount and type of fertilizer needed. Specific fertilizer types and recommended quantities vary widely from place to place and local practice should be followed. In all cases, check the local practice for the crop first.

Taro

Xanthosoma

Cyrtosperma

Weed management

Taro

Xanthosoma

Cyrtosperma

Common pests and diseases

Contact plant health experts to identify pest and disease symptoms and appropriate control measures. Some of the major pests and diseases of aroids are listed below:

Taro

Xanthosoma

Cyrtosperma

Harvesting

Normally harvesting is not required if the collection is ratooned, as it regrows in the same field (see When to regenerate, above). Take care during harvesting and subsequent handling not to bruise the cormels. Not all the accessions mature at the same time, even when they are categorised according to time to maturity.

Taro

Xanthosoma

Cyrtosperma

Harvest when:

Post-harvest management

Taro

Xanthosoma

Note that Xanthosoma can be stored in the ground for months or even years after reaching maturity. (See Harvesting.)

Cyrtosperma

Monitoring accession identity

Documentation of information during regeneration

The following information should be collected during regeneration:

References and further reading

Bioversity International. 2009. Key access and utilization descriptors for taro genetic resources. Bioversity International, Rome, Italy. Available here.

Brown D. 2000. Aroids. Plants of the Arum family (2nd ed.). Timber Press, Portland, Oregon, USA. 392 pp.

Clement CR. 1994. Crops of the Amazon and Orinoco regions: Their origin, decline and future. In: Hernaldo JE, León J, editors. Neglected crops: 1492 from a different perspective. Plant Production and Protection Series No. 26. FAO, Rome, Italy. pp. 195–203.

Coursey DC. 1968. The edible aroids. World Crops 20:25–30.

Denham T. 2004. Early agriculture in the highlands of New Guinea: an assessment of Phase 1 at Kuk Swamp. In: Attenbrow V, Fullagar R, editors. A Pacific Odyssey: Archaeology and Anthropology in the Western Pacific. Records of the Australian Museum, Supplement 29. Australian Museum, Sydney, Australia. pp. 47–57.

Edison S, Unnikrishnan M, Vimala B, Pillai SV, Shhela MN, Sreekumari MT, Abraham K. 2006. Biodiversity of tropical tuber crops in India. NBA Scientific Bulletin No. 7. National Biodiversity Authority, Chennai, India. 60 pp.

Giacometti DC, León J. 1994. Tannia. Yautia (Xanthosoma sagittifolium). In: Hernaldo JE, León J, editors. Neglected crops: 1492 from a different perspective. Plant Production and Protection Series No. 26. FAO, Rome, Italy. pp. 253–258.

Hay A. 1988. Cyrtosperma (Araceae) and its Old World allies. Blumea 33:427–469.

Hay A. 1990. Aroids of Papua New Guinea. Christensen Research Institute, PNG.

Hay A. 1998. Botanical varieties in taro, Colocasia esculenta: leaving old baggage behind. A report on taro consultancy No. CO2C. IPGRI, Rome, Italy. 13 pp.

Hernández Bermejo JE, León J, editors. 1994. Neglected crops: 1492 from a different perspective. Plant Production and Protection Series No. 26. FAO, Rome, Italy.

Hetterscheid W. 2004. Genera List (Cyrtosperma). International Aroid Society. Available from: http://www.aroid.org/genera/cyrtosperma/Cyrtospermalist.html. Date accessed: 1 August 2008.

IBPGR. 1989. Descriptors for Xanthosoma. IBPGR, Rome, Italy.

Iese V. 2005. Characterization of the giant swamp taro (Cyrtosperma chamissonis (Merr.) Schott) using morphological features, genetic fingerprinting and traditional knowledge of farmers in the Pacific. MSc Thesis. Biology Department, School of Pure and Applied Sciences, The University of the South Pacific, Suva, Fiji.

IPGRI. 1999. Descriptors for Taro (Colocasia esculenta). IPGRI, Rome, Italy.

Kreike CM, van Eck HJ, Lebot V. 2004. Genetic diversity of taro, Colocasia esculenta (L.) Schott, in Southeast Asia and the Pacific. Theoretical and Applied Genetics 109:761–768.

Lebot V. 1999. Biomolecular evidence for plant domestication in Sahul. Genetic Resources and Crop Evolution 46:619–628.

Matthews PJ. 1991. A possible tropical wildtype taro: Colocasia esculenta var. aquatilis. Indo-Pacific Prehistory Association Bulletin 11:69–81.

Matthews PJ. 2002. Potential of root crops for food and industrial resources. In: Potential of root crops for food and industrial resources. Twelfth Symposium of The International Society for Tropical Root Crops (ISTRC), 10–16 September 2000, Tsukuba, Japan. pp. 524–533.

Matthews PJ. 2002. Taro storage systems. In: Shuji Y, Matthews P, editors. Vegeculture in Eastern Asia and Oceania. JCAS Symposium Series 16. The Japan Center for Area Studies (JCAS), National Museum of Ethnology, Osaka, Japan. pp. 135–163.

Matthews PJ. 2004. Genetic diversity of taro, and the preservation of culinary knowledge. Ethnobotany Research & Applications 2:55–71.

Onokpise OU, Wutoh JG, Ndzana X, Tambong JT, Mekoba MM, Sama AE, Nyochembeng L, Aguegia A, Nzietchueng S, Wilson JG, Burns M. 1999. Evaluation of Macabo cocoyam germplasm in Cameroon. In: Janick J, editor. Perspectives on New Crops and New Uses.
ASHS Press, Alexandria, VA, USA. pp. 394–396.

Onwueme IC. 1978. Colocasia and Xanthosoma (Cocoyams). In: Onwueme IC. The Tropical Tuber Crops: yams, cassava, sweet potato, and cocoyam. J Wiley and Sons Ltd., New York, USA. pp. 589–606.

Onwueme IC, Charles WB. 1994. Cultivation of cocoyam. In: Tropical root and tuber crops. Production, perspectives and future prospects. FAO Plant Production and Protection Paper 126, FAO, Rome, Italy. pp. 139–161.

Plucknett DL. 1976. Edible aroids. In: Simmonds, NW, editor. Evolution of Crop Plants.
Longman Inc, New York, USA. pp. 10–12.

Shaw T. 1976. Early crop in Africa: A review of the evidence. In: Harlan JR, de Wit JMJ, Stemler ABL. Origins of African Plant Domestication. Mouton, The Hague, Netherlands. pp. 108–153.

Thompson S. 1982. Cyrtosperma chamissonis (Aracae): Ecology, distribution, and economic importance in the South Pacific. Journal d’ Agriculture Traditionalelle et de Botanique Applliquee 29(2):185–213.

Wilson JE. 1984. Cocoyam. In: Goldsworthy PR, Fisher NM, editors. The Physiology of Tropical Field Crops. John Wiley and Sons Ltd., New York, USA. pp. 589–605.

Acknowledgements

These guidelines have been peer reviewed by V. Ramanatha Rao, India, and Mary Taylor, Secretariat of the Pacific Community (SPC), Fiji.

The Genebanks

The 11 CGIAR genebanks currently conserve 730,000 of cereals and grain legumes, forage crops, tree species, root and tuber crops, bananas and crop wild relatives.

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