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Dioscorea wallichii (kruo)

A yam from Southeast Asia, India and China, Dioscorea wallichii has edible tubers that can grow to over one metre long.

Male plant of Dioscorea wallichii (kruo) just before flowers open

Male plant of Dioscorea wallichii (kruo) just before flowers open (showing stem twining direction, leaf shape, glossy upper surface of leaves and pigmented pulvinii).

Species information

Scientific name: 

Dioscorea wallichii Hook.f.

Common name: 

kruo (Chumporn, Thailand), kadat (Burma), gunga (Bangladesh), tunga, tunga sanga, tunga alu, tunga gaddi, tumangai, jugur kanda, cherango, dura sanga, bai-ili (India)

Conservation status: 

Least Concern (LC) according to IUCN Red List criteria.

Habitat: 

Mixed deciduous and evergreen forest.

Key Uses: 

Food.

Known hazards: 

None known.

Taxonomy

Subclass: 
Superorder: 
Lilianae
Order: 
Dioscoreales
Family: 
Dioscoreaceae
Genus: Dioscorea

About this species

Dioscorea wallichii was named by Joseph D. Hooker (1817-1911) in honour of Nathaniel Wallich (1786-1854), a surgeon and botanist who was involved in the development of the Botanic Garden, Calcutta. The tubers of D. wallichii are edible when boiled and peeled but are buried deep under the soil so they can be hard to extract.

Synonym: 

Dioscorea wallichii var. christiei Prain & Burkill, Dioscorea wallichii var. vera Prain & Burkill

Genus: 
Dioscorea

Discover more

Geography and distribution

Dioscorea wallichii (kruo) female specimen

Herbarium specimen of a female plant of Dioscorea wallichii with fruits.

Dioscorea wallichii is found in India, Bangladesh, Burma, Thailand and China. It climbs on large shrubs or trees in mixed deciduous forest and evergreen montane forest. It also occurs in disturbed areas along roadsides and edges of cultivated areas.

Description

Overview: A large, hairless climber that can grow to at least 20 m long. It has one edible, cylindrical tuber (or sometimes one that is used for growth whilst new one is forming) that can be over 1 m long and 3–6 cm wide. The tuber is white when young, becoming yellow and stringy with age.

Stem and leaves: The right-twining stem is woody and armed with spines at the base, herbaceous above and round in cross-section. Leaves are usually 8–19 x 8–21 cm and are more or less heart-shaped, with 5–7 main veins.

Flowers: Like almost all yams (Dioscorea species), D. wallichii has separate male and female plants. The female inflorescences (flowering structures) hang down from the vine, each one containing up to 20 flowers. Male inflorescences are also pendent, and the male flowers are green and about 1 mm long.

Fruits: Round capsules contain flat, brown seeds, each with a thin, marginal wing.

Threats and conservation

Common and widespread within its natural range, Dioscorea wallichii is not considered to be threatened. It appears to be tolerant of some disturbance, judging from the areas where it is found, hence the species is listed as Least Concern.

As with all edible species, it is desirable to monitor sustainability of use on a local level.

Dioscorea wallichii (kruo) male specimen

Herbarium specimen of Dioscorea wallichii (male plant).

Conservation assessments carried out at Kew

Dioscorea wallichii is being monitored as part of the IUCN Sampled Red List Index for Plants project, which aims to produce conservation assessments for a representative sample of the world’s plant species.

This information will then be used to monitor trends in extinction risk and help focus conservation efforts where they are needed most.

Uses

Tubers of Dioscorea wallichii are consumed on a local scale as a source of carbohydrates. They are eaten by ethnic groups such as the Sakai tribe, who live in the Banthad Range in Peninsular Thailand. They are also eaten by tribes in Orissa, India, during the winter months.

In other areas of India, D. wallichii has been described more as a famine food used in times of food shortage because the tubers are hard to extract and less desirable than those of other Dioscorea species.

In India, juice extracted from the tubers is drunk to treat jaundice.

This species at Kew

Pressed and dried specimens of Dioscorea wallichii are held in Kew’s Herbarium, where they are available to researchers from around the world by appointment. The details of some of these specimens can be seen online in Kew’s Herbarium Catalogue.

References and credits

Contu, S. (2009). Dioscorea wallichii. In: IUCN Red List of Threatened Species, Version 2011.2. <www.iucnredlist.org> (accessed 11 March 2012).

Edison, S. et al. (2006). Biodiversity of Tropical Tuber Crops in India. National Biodiversity Authority, Chennai, Tamil Nadu, India.

Maneenoon, K., Sirirugsa, P. & Sridith, K. (2008). Ethnobotany of Dioscorea L. (Dioscoreaceae), a major food plant of the Sakai Tribe at Banthad Range, Peninsular Thailand. Ethnobotany Research and Applications 6: 385–394.

Prain, D. & Burkill, I. H. (1938). An account of the genus Dioscorea in the East, Part 2: The species which twine to the right. Annals of the Royal Botanic Gardens, Calcutta 14: 211–528.

Sinha, R. & Lakra, V. (2005). Wild tribal food plants of Orissa. Indian Journal of Traditional Knowledge 4: 246–252.

Ting, C. & Gilbert, M. G. (2000). Dioscoreaceae. In: Flora of China. Available online (accessed on 19 March 2012).

Wilkin, P. & Thapyai, C. (2009). Dioscoreaceae. In: Flora of Thailand, ed. T. Santsuk & K. Larsen, pp. 1–140, The Forest Herbarium, Bangkok.

World Checklist of Selected Plant Families (2010). Dioscorea wallichii. The Board of Trustees of the Royal Botanic Gardens, Kew. Available online (accessed 3 March 2012).

Kew Science Editor: Malin Rivers and Patricia Malcolm
Kew contributors: Paul Wilkin, Lesley Walsingham
Copyediting: Emma Tredwell

While every effort has been taken to ensure that the information contained in these pages is reliable and complete, the notes on hazards, edibility and suchlike included here are recorded information and do not constitute recommendations. No responsibility will be taken for readers’ own actions.

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