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Solanum torvum Sw.

Protologue
Prodr.: 47 (1788).
Family
Solanaceae
Chromosome number
2n = 24, 48
Vernacular names
Pea eggplant, cherry eggplant, devil’s fig, plate brush, Turkey berry (En). Mélongène-diable, bellangère bâtarde, aubergine pois (Fr).
Origin and geographic distribution
Solanum torvum originates from Central and South America, where it is found from Mexico to Brazil and Peru, and is widespread in the Caribbean. It is now a pantropical weed. In West and Central Africa it is locally a kitchen garden crop, and it probably occurs in other regions of Africa as well. It is cultivated as a small-scale vegetable in southern and eastern Asia, and is especially popular in Thailand.
Uses
The bitter fruits are appreciated especially by elderly people and are used in soups and sauces or are chopped together with eggplant fruits or tomatoes. Solanum torvum is also used in traditional medicine. When used wisely, its fruit and leaves can be used to control a range of microbial activities. The glycoalkaloid solasodine that is found in its leaves and fruits is used in India in the manufacture of steroidal sex hormones for oral contraceptives. The antimicrobial properties of the leaves have been known for some time in Central America and India, and also in Gabon people apply the leaves to cuts and wounds. In Sierra Leone, the fruit in decoction is given to children as a cough medicine, whereas in Senegal the plant is taken to treat sore throat and stomachache. In India leaves are dried and ground to powder, which is used as medicine for diabetic patients. In Côte d’Ivoire the plant is known to cause instant insanity when eaten raw and it has been used as poison for people. On soils infested with Meloidogyne nematodes and bacterial wilt, Solanum torvum is occasionally used as a rootstock for eggplant and to a lesser extent for tomato. For the latter, Solanum aethiopicum cv. ‘Iizuka’ gives better results.
Production and international trade
Solanum torvum is becoming more popular in West Africa as a vegetable, especially in Ghana, and collected from the wild or from home gardens, both for direct consumption and for sale at local markets. No statistical data are available.
Properties
Per 100 g edible portion, young fruits contain: water 85.4 g, energy 197 kJ (47 kcal), protein 2.4 g, fat 0.4 g, carbohydrate 10.7 g, fibre 6.1 g, Ca 104 mg, P 70 mg, Fe 4.6 mg, β-carotene 390 μg, thiamin 0.12 mg, riboflavin 0.09 mg, niacin 2.6 mg, ascorbic acid 4 mg (Leung, W.-T.W., Butrum, R.R. & Chang, F.H., 1972). The leaves and fruits contain about 0.84% solasodine. In tests in India, dried fruits fried in oil and fed to mice caused hepatic tumours in 30% of the animals.
In tests in Nigeria, a methanolic extract of Solanum torvum fruits showed a wide spectrum of antimicrobial activities. The isoflavonoid torvanol A and the steroidal glycoside torvoside H isolated from the fruits showed antiviral activity against herpes simplex virus type 1. Studies on the effect of dried leaf powder in India showed no significant changes with respect to glucose, lipid profile, glycated proteins, total amino acids and uronic acid levels in non-insulin dependent diabetes mellitus patients. Solanum torvum is suspected of poisoning livestock.
Description
Spreading or scrambling slender shrub, up to 3(–4) m tall, pubescent with stellate hairs; stem and branches usually with scattered prickles 3–7 mm long, slightly hooked. Leaves alternate, solitary or in pairs, simple; stipules absent; petiole 1.5–5 cm long; blade ovate, 7–20 cm × 4–18 cm, usually coarsely and sinuously 7-lobed with triangular, acute to obtuse lobes, somewhat sagittate to auriculate at base. Inflorescence a compact, branched, up to 100-flowered corymb, at first terminal, later becoming lateral; peduncle 1–2 cm long. Flowers bisexual, regular, 5-merous; pedicel 5–10 mm long; calyx with lobes 3–4 mm long, persistent; corolla stellate, c. 2.5 cm in diameter, white, lobes lanceolate, c. 1 cm long; stamens inserted on corolla throat, filaments very short, anthers connivent, 6–7 mm long, opening by terminal pores; ovary superior, globose, pubescent, style 8–10 mm long, stigma capitate. Fruit a globose berry 1–1.5 cm in diameter, yellowish, many-seeded. Seeds discoid, 1.5–2 mm long, brownish. Seedling with epigeal germination.
Other botanical information
Solanum torvum is classified in section Torvum of subgenus Leptostemonum. This section comprises about 40 species, all of Central and South American origin. In South-East Asia cultivated types of Solanum torvum exist which are thornless.
Growth and development
Seeds require sunlight for germination, and shading may thus control the spread of Solanum torvum as a weed. The plant starts flowering after 3–4 months and continues flowering during its lifetime of up to 5 years. Birds and fruit bats eat the brownish yellow fruits and disperse the seeds through their droppings.
Ecology
Solanum torvum establishes itself on open land in disturbed soil, along roads and on waste places, where it often turns into a weed that becomes hard to control. In Cameroon it is a characteristic pioneer species on fallow land. It is listed as a noxious weed in the south-eastern United States. It is normally found either near wetlands or in high rainfall areas, mainly in lowland regions; yet it is tolerant of dry periods.
Management
Fruits of pea eggplant are mostly collected from the wild. In cultivation some care is required, including fertilizing and weeding when plants are young and irrigation, but pea eggplant is a very sturdy crop that grows without much care.
Propagation and planting
Solanum torvum is normally propagated by seed. The 1000seed weight is about 3.3 g. The fresh seed shows strong dormancy. Seed is sown in a nursery and seedlings are transplanted after 5–6 weeks at a spacing of 1 m. Branch cuttings taken from high-yielding shrubs are also used for propagation. Semi-hardwood cuttings 12–15 cm long, collected from fresh shoots and with their leaves removed, will produce roots and new shoots in 3–4 weeks.
Diseases and pests
Pea eggplant may suffer from some of the diseases that are found on other solanaceous crops, e.g. from Alternaria solani and eggplant anthracnose Colletotrichum gloeosporioides f. melongenae. The rust Aecidium habunguense causes orange pustules. Solanum torvum is sometimes damaged by aphids, Leucinodes fruit and shoot borers, leaf hoppers and Spodoptera caterpillars. It is a natural reservoir for the hemipterous eggplant lace bug Corythaica cyanthicollis (synonym Corythaica planaris) which attacks eggplant. A mosaic virus is transmitted by the aphids Aphis craccivora and Aphis gossypii. However, Solanum torvum is known for its resistance against soilborne pests and diseases, including Ralstonia solanacearum (the resistance, however, may break down at high temperatures), Verticillium dahliae, Thielaviopsis basicola, Phytophthora parasitica and Fusarium solani. It also appears to be resistant to flea beetles and Meloidogyne incognita. Unfortunately, crosses with the more important crops Solanum melongena L. and Solanum aethiopicum L. are not successful, but somatic hybridization with Solanum melongena has shown promise.
Harvesting
Clusters of immature green fruits are picked by the time that these have reached the size of a pea or cherry, depending on the cultivar. They can be picked for consumption in many successive rounds, starting 2 weeks after first flowering.
Handling after harvest
Pea eggplant is marketed in clusters of green, immature fruits rather than as individual fruit. The fruits can be kept for several days.
Genetic resources
Solanum torvum is an extremely widely distributed species with weedy characteristics, and thus not threatened by genetic erosion. Accessions of it are included in several germplasm collections of Solanum.
Breeding
In cultivation, African farmers use their own selected types. In Thailand seed of improved local cultivars is commercially available, e.g. at East West Seed Company. One cultivar is lacking prickles and another has a compact growth habit, both having big, less bitter fruits. Some Western seed catalogues offer seed for rootstock production.
Prospects
Pea eggplant is locally a popular traditional vegetable. Selection of improved cultivars might enhance interest for commercial production. However, attention should be paid to the possible adverse effects of fruit consumption.
Major references
• Boonkerd, T., Na Songkhla, B. & Thephuttee, W., 1993. Solanum torvum Swartz. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 258–260.
• Burkill, H.M., 2000. The useful plants of West Tropical Africa. 2nd Edition. Volume 5, Families S–Z, Addenda. Royal Botanic Gardens, Kew, United Kingdom. 686 pp.
• Messiaen, C.-M., 1989. Le potager tropical. 2nd Edition. Presses Universitaires de France, Paris, France. 580 pp.
• Schippers, R.R., 2000. African indigenous vegetables. An overview of the cultivated species. Natural Resources Institute/ACP-EU Technical Centre for Agricultural and Rural Cooperation, Chatham, United Kingdom. 214 pp.
Other references
• Ali, M., Matsuzoe, N., Okubo, H. & Fujieda, K., 1992. Resistance of non-tuberous Solanum to root-knot nematode. Journal of the Japanese Society for Horticultural Science 60: 921–926.
• Arthan, D., Svasti, J., Kittakoop, P., Pittayakhachonwut, D., Tanticharoen, M. & Thebtaranonth, Y., 2002. Antiviral isoflavonoid sulfate and steroidal glycosides from the fruits of Solanum torvum. Phytochemistry 59(4): 459–463.
• Balachandran, B. & Sivaramkrishnan, V.M., 1995. Induction of tumours by Indian dietary constituents. Indian Journal of Cancer 32(3): 104–109.
• Chah, K.F., Muko, K.N. & Oboegbulem, S.I., 2000. Antimicrobial activity of methanolic extract of Solanum torvum fruit. Fitoterapia 71(2): 187–189.
• Date, H., Nasu, H. & Hatamoto, M., 1994. Breakdown of resistance of eggplant rootstock (Solanum torvum Swartz) to bacterial wilt by high ambient temperature. Annals of the Phytopathological Society of Japan 60: 483–486.
• Iyer, U.M., Mehta, N.C., Mani, I. & Mani, U.V., 1992. Studies on the effect of dry sundakai (Solanum torvum) powder supplementation on lipid profile, glycated proteins and amino acids in non-insulin dependent diabetic patients. Plant Foods for Human Nutrition 42(2): 175–182.
• Jarl, C.I., Rietveld, E.M. & de Haas, J.M., 1999. Transfer of fungal tolerance through interspecific somatic hybridisation between Solanum melongena and S. torvum. Plant Cell Reports 18: 791–796.
• Leung, W.-T.W., Butrum, R.R. & Chang, F.H., 1972. Food composition table for use in East Asia. Department of Health, Education and Welfare, Bethesda, United States. 334 pp.
• Mian, I.H., Akhter, R. & Islam, M.N., 1995. Resistance of tomato and wild Solanum to Meloidogyne incognita. Bulletin of the Institute of Tropical Agriculture, Kyushu University 18: 33–40.
• Morra, L., 1998. Potential and limits of grafting in horticulture. Informatore Agrario 54(49): 39–42.
• Ndam, N. & Healey, J., 2000. Woody plants recovery in abandoned farms of different ages in the Mount Cameroon region. In: Robbrecht, E., Degreef, J. & Friis, I. (Editors). Plant systematics and phytogeography for the understanding of African biodiversity. Proceedings of the 14th AETFAT Congress, held at the National Botanic Garden, Belgium, 28 August - 2 September 2000. Systematics and Geography of Plants 71(2): 817-826.
• Suzuki, T. & Morishita, M., 2002. Effects of scion and rootstock cultivars on growth and yield of eggplant cultured under two fertilizer levels. Journal of the Japanese Society for Horticultural Science 71(4): 568–574.
Sources of illustration
• Boonkerd, T., Na Songkhla, B. & Thephuttee, W., 1993. Solanum torvum Swartz. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 258–260.
Author(s)
R.R. Schippers
De Boeier 7, 3742 GD Baarn, Netherlands


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:
Schippers, R.R., 2004. Solanum torvum Sw. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
Distribution Map wild and planted


flowering and fruiting branch.
Source: PROSEA



flowering and fruiting branch