The use and conservation of indigenous leafy vegetables in South Africa

Erika van den Heever
Vegetable and Ornamental Plant Institute, Agricultural Research Council, Pretoria, South Africa

Introduction

South Africa is a country of national food self-sufficiency, and is able to export food. However, hunger and malnutrition are still found in many rural and urban areas. It has been estimated that in South Africa at least 3 million people under the age of 15 are suffering from malnutrition (FRD 1992). Vegetables are of great importance in helping to alleviate this problem as they contribute significantly to the amount of calories and other nutrients in the diet. The scarcity of vegetables, or their scarcity in the diet, is a major cause of vitamin A deficiency, which causes blindness and even death in young children throughout the semi-arid and arid areas of Africa (Okigbo 1990).

Exotic vegetable species cannot be grown under the harsh climatic and resource-poor conditions encountered in many of the rural areas where these problems occur. However, there are a number of indigenous and traditionally grown plant species which could help to alleviate this situation. The use of wild plant foods in regions with low agricultural potential or during periods of drought contributes to food security and provides dietary supplements to the staple diet. Many of these plants, few of which are grown under improved husbandry, are eminently well suited for cultivation in the large areas of southern Africa which have low agricultural potential due to low or unreliable rainfall, poor soils and steep topography (Cunningham et al. 1992).

The use of wild plants as leafy vegetables is very common in South Africa and some of these species are also very popular, but some species are more sought after than others. The most popular species in South Africa are discussed below.

Taraxacum officinale, dandelion (Asteraceae)

This yellow-flowered perennial is a storehouse of vitamins and every part - root, leaf, flower and sap - is useful to humans. The leaves can be used as a source of vitamins A and C before the plants flower. The roots can be dried, baked, percolated and used as a coffee substitute. The sap of the plant is a source of latex. The flowers have a high carotene content. The leaves are used as greens, cooked with water, vinegar or meat (Duke 1992).

Bidens pilosa, blackjack (Asteraceae)

This plant is found throughout tropical Africa. Only the young leaves and shoots are edible, cooked like spinach. Blackjack is prepared with the leaves of pumpkin and one of the Coccinia species. It is widely harvested as a weed, but is also cultivated. It is most commonly dried for winter use. Young plants are said to have a high nutritive value, although the leaf has an astringent taste (Fox and Young 1982).

Chenopodium album, common lambsquarter (Chenopodiaceae)

The plant is pulled out of the ground, washed, boiled lightly, smothered in butter and used as a spinach. Tops can be eaten before and after flowering. The roots are used as an infusion for urethral itch or poulticed onto burns (Duke 1992).

Cleome gynandra, bastard mustard (Capparidaceae)
Cleome monophylla

The young plants are edible and are cultivated by several communities. It is widespread throughout tropical Africa. Cleome has some medicinal properties, being rubbed onto the skin to relieve pneumonia; as an infusion it is used as an eyewash (Tregold et al. 1986).

Portulaca oleracea, common purslane (Portulacaceae)

Tender parts, leaves, flowers, pods, seeds and stems may be stewed and used as potherbs, improved by adding egg and/or breadcrumbs. The pot-herb tastes like a slimy spinach. The medicinal uses are infusions for ear-ache, treatment for worms and poultice for bruises and burns. It is also used for pain and stomach-ache, boils, bug bites, colic, dermatitis, indigestion and snake bite (Duke 1992).

Amaranthus, pigweed (Amaranthaceae)

These plants have not yet received any attention from agricultural scientists in South Africa, as they have not been considered to show promise as a commercial crop. Amaranthus is one of the oldest food crops in the new world, with evidence of cultivation reaching back as far as 6700 BC (Agogino 1957; MacNeish 1971). This is probably owing to the ability of these plants to adapt readily to new environments, an extremely broad climatic adaptability and their competitive ability which permits cultivation with minimum management. This makes it an easy crop to cultivate and domesticate (Feine et al. 1979). This genus contains about 800 species and is divided into two sections. The section Amaranthus includes those species which are normally considered to be grain types, while the section Blitopsis includes the vegetable species. Amaranthus constitutes an important part of the diet in areas of South America, Africa and Asia (Grubben 1976). Although it is also used as a grain, Amaranthus is more widely used as a pot-herb and in some instances supplies a substantial portion of the protein, minerals and vitamins in the diet (Feine et al. 1979).

The leaves of all Amaranthus species are edible and many appear regularly in the diets of several societies (Grubben 1976; Larkcom 1991). Green leafy vegetables are an important source of vitamins in poor communities. Amaranthus is a good source of vitamin A for preschool children and has been found to be readily utilizable (Feine et al. 1979). There are several species in South Africa, namely A. cruentus, A. hybridus, A spinosus, A. caudatus and A. thunbergii, which are all indigenous to the country.

Vigna unguiculata, cowpea (Fabaceae)

The cowpea is used both as a vegetable and for its seed. The semi-spreading types are suitable for use as a vegetable. The leaves are picked 4 weeks after planting, and this continues until the plants start to flower. The leaves are dried for later use and cooked as spinach.

The use and conservation of indigenous leafy vegetables

These indigenous leafy vegetables have the potential to provide a valuable source of nutrition in areas with hot, dry climates. They could fill a valuable niche in the production of food in rural areas where the climate is not conducive to the production of vegetables such as spinach or swiss chard. They could be particularly valuable in areas with a low rainfall, as these crops will produce a viable yield under these conditions, whereas most of the exotic leafy vegetables require large amounts of water for successful production. In areas where people have to walk long distances to collect their water, most water is used for household purposes and there is very little available for use on a vegetable garden. Drought-tolerant vegetable crops would be invaluable in helping to alleviate malnutrition in these areas. However, before being able to fulfil this potential, more information on their cultivation requirements is required. Also, careful attention should be paid to palatability if a plant is to be successfully grown as a commercial crop.

Clearly, conservation of the various indigenous vegetable species must be a priority. Emphasis has been placed on the establishment of an Agricultural Research Council Gene Bank as a long-term facility that conforms to international standards. A documentation system will soon be in place. The next major step will be the upgrading of the new genebank, including in vitro storage facilities. This project is already providing valuable information to the international and national scientific community. The upgrading of the existing facility will improve this service and enhance the Agricultural Research Council's (ARC) image considerably.

The long-term aims and objectives of the new ARC genebank are:

· to conserve and maintain accessions in accordance with established international plant genetic resource criteria

· to develop and maintain a supporting documentation system that will add value to accessions conserved and maintained in the ARC genebank

· to supply germplasm to ARC scientists for description, characterization, evaluation and breeding

· to supply germplasm to other organizations in South Africa

· to supply germplasm for international exchange.

The genebank has only recently started to conform to international standards. The establishment of a Plant Genetic Resources Unit in the ARC (ARC/PGR Unit) in April 1995 is leading to the development of a professional plant genetic resources service and function within the ARC based on internationally accepted standards for the management of plant germplasm within a cooperative national and international context. The objective of the ARC/PGR Unit is to make provision for coordination and liaison with international and regional plant genetic resources organizations as well as other key players in South Africa.

The Vegetable and Ornamental Plant Institute project on indigenous leafy vegetables

The objectives of the project are as follows:

· develop appropriate cultivation practices

· start a selection and breeding programme to improve the yield, quality and adaptability of promising species

· develop in vitro and other vegetative techniques to enable rapid multiplication of promising lines for use in the project and later to supply to producers

· execute on-farm research in various areas of the country to test acceptability and adaptability of the plants

· test the nutritional status of the plants

· test the value of these plants in intercropping systems

· promote the use of these plants as substitutes for, or to be grown in conjunction with, the present crops, where they are better adapted than the current commercial crops.

Genebank collections of various crops will be evaluated in the field and selected for further evaluation in terms of yield, field resistance to pests and diseases, ease of production, nutritional status and acceptance for human consumption. Intercropping methods and systems as practised by small farmers also will be evaluated. All research will be performed as on-farm trials in the appropriate regions after an assessment of the needs of each community has been performed.

The use of indigenous vegetables is declining in all areas in South Africa, and the material and knowledge of its use are disappearing at an alarming rate. Communities and people would like the plants reintroduced because of their usefulness and nutritional value. The Vegetable and Ornamental Plant Institute is preparing a conservation programme in cooperation with Roodeplaat Field Institute and Centre for Low Input Agricultural Research and Development (CLIARD), an NGO based at the University of Zululand. The proposal has been submitted to the European Union for funding. Even if the required funding is not forthcoming from the European Union, this project will go ahead, albeit at a much slower rate. The envisaged system consists of a herbarium, passport data-processing system, collecting, introduction, maintenance, conservation and evaluation of the plants, with research leading to improvement of the plants and eventually crop improvement and increased utilization.

References

Agogino, G.A. 1957. Sci. Newsletter, Washington 72:345.

Cunningham, A.B., P.J. de Jager and L.C.B. Hansen. 1992. The indigenous plant use programme. Foundation for Research Development, Pretoria.

Duke, James A. 1992. Handbook of Edible Weeds. CRC Press, London.

Feine, B., R.R. Harwood, C.S. Kauffman and J.P. Senft. 1979. Amaranth: Gentle giant of the past and future. Chap. 3 in New Agricultural Crops (G.A. Ritchie, ed.). Westview Press, Boulder, Colorado.

Fox, F.W. and M.E. Norwood Young. 1982. Food from the Veld. Edible Wild Plants of Southern Africa. Delta Books.

FRD. 1992. Rural poverty alert; Challenging Science and Technology. Foundation for Research Development, Pretoria.

Grubben, G.J.H. 1976. The Cultivation of Amaranth as a Tropical Leaf Vegetable. Royal Tropical Institute, Amsterdam.

Larkcom, Joy. 1991. Oriental Vegetables. The Complete Guide for Garden and Kitchen. John Murray Publishers Ltd., London.

MacNeish, R.S. 1971. Archaeology 24:307.

Okigbo, B.N. 1990. Vegetables in Tropical Africa. Pp. 29-52 in Vegetable Research and Development in SADCC Countries (R.T. Opena and M.L. Kyomo, eds.). Proceedings of a workshop held at Arusha, Tanzania, 9-13 July 1990. AVRDC Publication No. 90-328. Asian Vegetable Research and Development Centre, Taiwan.

Tregold, N.H., H.M. Biegel, S. Mavi and H. Ashton. 1986. Food of Zimbabwe. Mambo Press, Bulawayo.