Canavalia gladiata (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Vegetable
Medicinal
Ornamental
Forage / feed
Food security

distribution in Africa (planted)

1, part of flowering stem; 2, inflorescence with young fruits; 3, seeds. Source: PROSEA

Canavalia gladiata (Jacq.) DC.

Protologue: Prodr. 2: 404 (1825).

Family: Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)

Chromosome number: 2n = 22, 44

Vernacular names

• Sword bean, sword jackbean, Japanese jackbean (En).
• Pois sabre, pois sabre rouge, haricot sabre (Fr).
• Fava-contra (Po).
• Mwingasiafu, mbwanda (Sw).

Origin and geographic distribution

Sword bean is only known cultivated and naturalized. Its origin is in the Old World tropics and it was probably domesticated in eastern Asia. The wide dispersal in historic times is thought to be partly due to carrying the remarkable seeds as curios.

Uses

In Madagascar the young green fruits and immature seeds of sword bean are used as a cooked vegetable. Sword bean is eaten in Tanzania, where the Swahili expression ‘eating sword bean’ means ‘being happy’. Use of the fruits and immature seeds is also reported from Sri Lanka, India, Indonesia, China, Korea and Japan. Sword bean is further planted as a forage and cover crop. The ripe seeds can be eaten after cooking, but only after removing the seed-coat and several changes of water. The seed is used as feed for cattle and chicken, but if eaten in considerable quantity dry seeds may cause poisoning. Sword bean is grown as an ornamental climber on fences and houses.

Urease is extracted from the seed; it is used in clinical laboratories for the in-vitro determination of urea in human blood. In Korea it is used in the treatment of vomiting, abdominal dropsy, kidney-related lumbago, asthma, obesity, stomach-ache, dysentery, coughs, headache, intercostal neuralgia, epilepsy, schizophrenia, inflammatory diseases and swellings. In Japan it is effective in treating ozena, haemorrhoids, pyorrhea, otitis media, boils and cancers, all kinds of inflammatory diseases and atopic dermatitis. In Korea soap is marketed based on extracts of sword bean; it is used for the treatment of athlete’s foot and acne.

Production and international trade

No information is available on the trade of sword bean as a vegetable. Seeds of Canavalia are traded internationally for the production of urease, but quantities of seed entering the international market are not known.

Properties

The nutritional composition of fresh sword bean fruits per 100 g edible portion is: water 83.6 g, energy 247 kJ (59 kcal), protein 4.6 g, fat 0.4 g, carbohydrate 10.7 g, fibre 2.6 g, Ca 33 mg, P 66 mg, Fe 1.2 mg, vitamin A 40 IU, thiamin 0.2 mg, riboflavin 0.1 mg, niacin 2 mg, ascorbic acid 32 mg. Dry seeds contain per 100 g: water 10.7 g, energy 1453 kJ (347 kcal), protein 24.5 g, fat 2.6 g, carbohydrate 59 g, fibre 7.4 g, Ca 158 mg, P 298 mg, Fe 7.0 mg, thiamin 0.8 mg, riboflavin 1.8 mg, ascorbic acid 1 mg (Rubatzky, V.E. & Yamaguchi, M., 1997). The seed protein is poor in methionine, but rich in lysine.

The seeds of Canavalia species contain several growth-inhibiting and toxic storage proteins, e.g. canavalin (vicilin), con-canavalin A and B and canatoxin. The urease contained in the seed is chemically related to canatoxin. It also contains the toxic non-protein amino acid canavanine, a structural analogue of L-arginine. In both human and animal nutrition dry seeds have the shortcoming that their proteins have a low digestibility and a low biological value, and raw seeds are poisonous in large quantities. The digestibility can be improved by treatment such as heating (prolonged cooking, pressure-cooking or roasting) or fermenting.

There are numerous publications of results of research into the chemical composition of several Canavalia species. Seed protein content and composition of Canavalia gladiata and Canavalia ensiformis (L.) DC. are similar.

Adulterations and substitutes

Alternative sources of urease are various bacteria (e.g. Klebsiella aerogenes), fungi (e.g. Coccidioides immitis) and higher plants (e.g. soya bean).

Description

• Perennial trailing or climbing herb up to 10 m long, often grown as an annual; root system deep.
• Leaves alternate, pinnately 3-foliolate; stipules small, deciduous; petiole 5–17 cm long; leaflets with 4–7 mm long stalks, ovate, 7.5–20 cm × 5–14 cm, apex acuminate, shortly pubescent on both sides.
• Inflorescence an axillary raceme 7–12 cm long; peduncle 4–20 cm long.
• Flowers bisexual, papilionaceous, often resupinate; calyx up to 1.5 cm long, 2-lipped with a large 2-fid upper lip and a much smaller 3-fid lower lip; corolla white, standard c. 3.5 cm long; stamens 10, all joined; ovary superior, style slender, curved, stigma small.
• Fruit a linear-oblong pod, slightly compressed, sometimes curved, 20–40(–60) cm × 3.5–5 cm, widest near the apex, 8–16-seeded, spirally dehiscent; each valve with ventral rib and extra rib spaced c. 4 mm.
• Seeds 2–3.5 cm × 1.5–2 cm, red or red-brown, rarely black, pink or white; hilum 1.5–2.0 cm long.
• Seedling with epigeal germination; first 2 leaves simple, opposite, with stipules connate.

Other botanical information

Canavalia comprises about 60 species, most of these of American origin. There are many reports in the literature of the occurrence of the sword bean in tropical Africa, but there are few herbarium specimens from Africa. Many of the reports likely refer to the widespread indigenous Canavalia africana Dunn (synonym: Canavalia virosa auct. non (Roxb.) Wight & Arn.). In the interior of tropical Africa at higher altitudes (over 300 m) Canavalia africana is the most common indigenous Canavalia species. It is occasionally cultivated as a cover crop and green manure. The seeds are eaten in Ethiopia and Tanzania, but often only as a famine food. In Tanzania the leaves are used in a recipe for treating smallpox. In India, where Canavalia africana occurs as well, researchers have named plants collected in the wild Canavalia gladiata. Jackbean (Canavalia ensiformis) is considered a native of the New World and is only known in cultivation. It is widely grown in Africa but mainly as a cover crop, forage, green manure and ornamental. The use of its fruits and immature seeds seems fairly common in Asia but substantiated reports of use as a vegetable in Africa are lacking. The 3 above-mentioned taxa are considered by some as a single species as they cross freely and their uses and chemical composition are similar. Also, an analysis based on DNA data designed to distinguish legume species failed to find differences between Canavalia ensiformis and Canavalia gladiata. However most floras separate the 3 species as follows:

Canavalia gladiata: standard c. 3.5 cm long, white; fruit 20–40(–60) cm × 3.5–5 cm; seeds red or red-brown, rarely white, 2–3.5 cm long, hilum 1.5–2 cm long.

Canavalia ensiformis: standard c. 2.5 cm long, pink to purple; fruit 15–35 cm × 3–3.5 cm; seeds ivory or white, 1.5–2 cm long, hilum 0.5–1 cm long.

Canavalia africana: standard c. 3 cm long, white with mauve veins; fruit 10–17 cm × 2.5–3 cm; seeds brown or red-brown, 1.5–2 cm long, hilum 1–1.5 cm long.

Cultivars of Canavalia ensiformis vary widely, particularly in the degree of twining, the size of the fruits and the number and colour of the seeds.

Growth and development

Sword bean seed germinates readily and the plant is relatively fast growing. Flowers are pollinated by insects and 20% or more cross-pollination occurs.

Ecology

Sword bean requires temperatures of 20–30°C and is cultivated from sea-level up to 1000 m altitude. It is tolerant of drought once established and also tolerant of waterlogging, shade and salinity, making it one of the most hardy tropical legumes. It prefers an evenly distributed annual rainfall of 900–1500 mm. It grows well even on nutrient depleted soils and on acid soils, even with a pH as low as 4.5.

Propagation and planting

Sword bean is usually grown by smallholder farmers near houses and allowed to climb on walls, fences and trees. Seeds are sown at a depth of 5–7.5 cm. As a field crop, it is usually sown at a spacing of 75–90 cm between rows and 45–60 cm within the row, at a seed rate of 25–40 kg/ha.

Management

To avoid a build up of pests and diseases it is recommended that sword bean be treated as an annual crop or retained at most for 2 years.

Diseases and pests

Sword bean is fairly resistant to diseases and pests. The most serious fungal disease is root rot caused by Colletotrichum lindemuthianum. Sword bean is a host of tomato spotted wilt virus (TSWV). Canavalia is known to reduce nematode populations. However, it is susceptible to the soybean cyst nematode (Heterodera glycines) that has not yet been recorded in Africa. Major pests are fall army worm (Spodoptera frugiperda) and beetle grubs that bore into the stems. Sword bean seeds are fairly resistant to storage pests.

Harvesting

Young sword bean fruits can be harvested from 3–4 months after sowing when they are 10–15 cm long, before they swell and become fibrous and tough. Mature seed can be harvested after 5–10 months. As the fruits shatter their seeds when ripe, harvesting should be done timely.

Yield

Yields of green fruits can be up to 4 t/ha. Forage yields of up to 60 t/ha have been reported. Seed yields of up to 5.4 t/ha are possible, but a seed yield of 1.5 t/ha is more common.

Genetic resources

Worldwide collection of Canavalia germplasm is urgently needed. Small germplasm collections of Canavalia are maintained at the Australian Tropical Crops & Forages Genetic Resources Centre, Biloela, Queensland. A few accessions are available in Ethiopia (ILRI), Nigeria (IITA), South Africa, Brazil, China, Colombia and India.

Breeding

Sword bean is not known from the wild and must have undergone selection during centuries. Selection has favoured increased pod and seed size but has not resulted in a reduction in biochemical toxins. This would be consistent with selection for use as fodder or as a green fruit vegetable rather than as a pulse crop. Breeding is difficult as the flowers are very sensitive to damage during emasculation and emasculated flowers usually abscise; therefore bud pollination is recommended. In South-East Asia sword bean cultivars have been developed with reduced toxicity. Hybrids of Canavalia gladiata with both Canavalia africana and Canavalia ensiformis have occurred from natural crosses. Breeding programmes should use this wide base of germplasm.

Prospects

To increase the use of Canavalia green fruits and young seeds as a vegetable in tropical Africa, improved cultivars should be made available either by introducing Asian cultivars or by breeding. Major limitations for increased use of the dry seeds of Canavalia in human nutrition are the poor taste, the unappealing texture and antinutritional factors that make laborious preparation necessary. In these respects Canavalia faces the same acceptability problems in Africa as soya bean. However, as Canavalia is a very tough and resilient crop it could play a larger role if seeds were produced in quantity and processed on an industrial scale. Breeding and selection could play a role in developing cultivars with reduced toxicity. Sword bean will remain important as a green manure and cover crop and as fodder. A critical review of the taxonomy of the genus Canavalia is overdue.

Major references

• Duke, J.A., 1981. Handbook of legumes of world economic importance. Plenum Press, New York, United States, and London, United Kingdom. 345 pp.

• Emebiri, L.C., 1996.. Evaluation of the jackbean (Canavalia ensiformis) lines derived from natural crossing with swordbean (Canavalia gladiata). Biological Agriculture and Horticulture 12(4): 319–325.

• ILDIS, 2002. World database of Legumes, Version 6,05. International Legume Database & Information Service. [Internet] http://www.ildis.org/. March 2004.

• Kooi, G., 1993. Canavalia gladiata (Jacq.) DC. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 134–136.

• Mackinder, B., Pasquet, R., Polhill, R. & Verdcourt, B., 2001. Leguminosae (Papilionoideae: Phaseoleae). In: Pope, G.V. & Polhill, R.M. (Editors). Flora Zambesiaca. Volume 3, part 5. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 261 pp.

• Rubatzky, V.E. & Yamaguchi, M., 1997. World vegetables: principles, production and nutritive values. 2nd Edition. Chapman & Hall, New York, United States. 843 pp.

• Verdcourt, B., 1987. Three corrections to the Flora of Tropical East Africa. Kew Bulletin 42(3): 657–660.

Other references

• Adema, F., 1997. Notes on Malesian Fabaceae (Leguminosae-Papilionoideae) 2. The Genus Canavalia Adans. Blumea 42(1): 249–253.

• Chee, Y.K., Hacker, J.B., Ramirez, L. & Chen, C.P., 1992. Canavalia ensiformis (L.) DC. In: ’t Mannetje, L. & Jones, R.M. (Editors). Plant Resources of South-East Asia No 4. Forages. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 74–77.

• du Puy, D.J., Labat, J.N., Rabevohitra, R., Villiers, J.-F., Bosser, J. & Moat, J., 2002. The Leguminosae of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 750 pp.

• Ekanayake, S., Jansz, E.R. & Nair, B.M., 2000. Literature review of an underutilized legume: Canavalia gladiata L. Plant Foods for Human Nutrition 55(4): 305–321.

• Ekanayake, S., Jansz, E.R. & Nair, B.M., 2000. Nutritional evaluation of protein and starch of mature Canavalia gladiata seeds. International Journal of Food Sciences and Nutrition 51: 289–294.

• Gillett, J.B., Polhill, R.M., Verdcourt, B., Schubert, B.G., Milne-Redhead, E., & Brummitt, R.K., 1971. Leguminosae (Parts 3–4), subfamily Papilionoideae (1–2). In: Milne-Redhead, E. & Polhill, R.M. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 1108 pp.

• Kamuhabwa, A., Nshimo, C. & de Witte, P., 2000. Cytotoxicity of some medicinal plant extracts used in Tanzanian traditional medicine. Journal of Ethnopharmacology 70: 143–149.

• National Academy of Sciences, 1979. Tropical legumes: resources for the future. National Academy of Sciences, Washington, D.C., United States. 331 pp.

• Oliveira, A.E.A., Sales, M.P., Machado, O.L.T., Fernandes, K.V.S. & Xavier-Filho, J., 1999. The toxicity of Jack bean (Canavalia ensiformis) cotyledon and seed coat proteins to the cowpea weevil (Callosobruchus maculatus). Entomologia Experimentalis et Applicata 92: 249–255.

• Polhill, R.M., 1990. Légumineuses. In: Bosser, J., Cadet, T., Guého, J. & Marais, W. (Editors). Flore des Mascareignes. Famille 80. The Sugar Industry Research Institute, Mauritius, l’Office de la Recherche Scientifique Outre-Mer, Paris, France & Royal Botanic Gardens, Kew, Richmond, United Kingdom. 235 pp.

• Sauer, J.D., 1964. A revision of Canavalia. Brittonia 16: 106–181.

• Smartt, J., 1990. Grain legumes: evolution and genetic resources. Cambridge University Press, Cambridge, United Kingdom. 379 pp.

• Sosef, M.S.M. & van der Maesen, L.J.G., 1997. Minor auxiliary plants. In: Faridah Hanum, I. & van der Maesen, L.J.G. (Editors). Plant Resources of South-East Asia No 11. Auxiliary plants. Backhuys Publishers, Leiden, Netherlands. pp. 264–307.

• Udedibie, A.B.I. & Carlini, C.R., 1998. Questions and answers to edibility problem of the Canavalia ensiformis seeds - A review. Animal Feed Science and Technology 74: 95–106.

• Vadivel, V., Janardhanan, K. & Vijayakumari, K., 1998. Diversity in sword bean (Canavalia gladiata (Jacq.) DC.) collected from Tamil Nadu, India. Genetic Resources and Crop Evolution 45(1): 63–68.

• Weder, J.K.P., 2002. Identification of food and feed legumes by RAPD-PCR. Food Science and Technology 35: 504–511.

• Westphal, E., 1974. Pulses in Ethiopia, their taxonomy and agricultural significance. Agricultural Research Reports 815. Centre for Agricultural Publishing and Documentation, Wageningen, Netherlands. 263 pp.

Sources of illustration

• Kooi, G., 1993. Canavalia gladiata (Jacq.) DC. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 134–136.

Author(s)

• C.H. Bosch, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Bosch, C.H., 2004. Canavalia gladiata (Jacq.) DC. [Internet] Record from PROTA4U. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands.

Accessed 18 December 2024.