White Cropped

Re-discover Some of the Underutilized and Neglected Crops of the World With a View to Broaden our Food Resource Base: Bambara Groundnut

Know the underutilized and neglected crops of the World.

1) Bambara Groundnut (Vigna subterranea (L.) Verdc.)

Background

Most human food requirements are provided by fewer than 20 crop species. There remains a vast repository of many hundreds of underutilised species that have been grown locally for centuries and which contribute to the food security of the world's poorest people. Many of these crops are cultivated in hostile, tropical environments by small-scale farmers without access to irrigation or fertilizers and with little guidance on improved practices and feasible alternatives. Any attempts to improve their germplasm or management practices depend on local experience and resources since most agricultural scientists and breeders have ignored or actively discouraged the cultivation of indigenous underutilised crops. The few efforts that have been made to evaluate these species by conventional methods have been slow and labour-intensive and research funds have rarely been directed to multidisciplinary research on such crops of unknown potential. Furthermore, because many of these crops are grown for subsistence, little effort has been made to genetically or agronomically improve them or assess their nutritional, processing and economic potential.

A major limitation of most research on underutilised crops is that, because of inadequate funding, it is confined to a single aspect, e.g. breeding, of the particular species in question. The lack of a multidisciplinary effort or comprehensive published literature on any particular underutilised species means that any research that is done may duplicate that being done elsewhere with no increase in overall knowledge or understanding of the crop in question. The lack of an overarching strategy for the improvement of different underutilised crops discourages the development of general principles that can be applied across species. This piecemeal approach reduces both the effectiveness of research on each underutilised species and the collective influence of those advocating greater efforts to increase agricultural biodiversity.

If there is to be an increase in agricultural biodiversity and a broader basis to food security policies, there is an urgent need to coordinate research on underutilised crops within a general and robust methodology that:

1. Disseminates recommendations to growers and advisors on management practices and end uses.

2. Defines physiological attributes and responses to environmental factors so that the agro-ecological requirements of each crop can be determined.

3. Identifies how knowledge and understanding gained on any particular species can rapidly be applied to increase our understanding of other underutilised crops.

One such crop is Bambara groundnut (Vigna subterranea L. Verdc), which is an indigenous grain legume grown mainly by subsistence women farmers in drier parts of sub-Saharan Africa. The crop has advantages over more favoured species in terms of nutritional value and tolerance to adverse environmental conditions. In much of Africa, Bambara groundnut is the third most important legume after peanuts (Arachis hypogaea) and cowpea (Vigna unguiculata) (Sellschop, 1962). The crop has a number of production advantages in that it can yield on poor soils with little rainfall as well as produce substantial yields under better conditions. It is nutritionally superior to other legumes and is the preferred food crop of many local people (Linnemann, 1990; Brough and Azam-Ali, 1992). Bambara groundnut is a rich source of protein (16-25%) and its seeds are valued both for their nutritional and economic importance. The seeds command a high market price, with demand far outweighing supply in many areas (Coudert, 1982). However, despite these important attributes, the agro-ecological and genetic potential of Bambara groundnut have not yet been fully realized nor its full economic significance determined. The crop is still cultivated from local landraces rather than varieties bred specifically for particular agro-ecological conditions or production systems.

Recently, scientists in Africa and elsewhere have begun to accumulate agronomic and physiological knowledge about the crop and to link this with the indigenous knowledge and perceptions of farmers. Between 1992 and 1996, the University of Nottingham, UK, co-coordinated a major European Union (EU) project to assess the agro-ecological potential of Bambara groundnut. This programme linked field experiments in the United Republic of Tanzania, Botswana and Sierra Leone with experiments and analysis at Nottingham and Wageningen University in the Netherlands. The objectives of the EU Bambara Groundnut Project were to:

1. Define sites and seasons for Bambara groundnut cultivation in the United Republic of Tanzania, Botswana and Sierra Leone.

2. Produce a validated, mechanistic model of Bambara groundnut to predict total biomass and pod yield in contrasting soil and atmospheric environments.

3. Identify attributes associated with the ability to produce yields under semi-arid conditions.

4. Recommend management practices to stabilise crop yields under rain fed conditions.

5. Outline a methodology for applying a similar approach to rapidly assess the potential of other underutilised species.

Bambara groundnut has become less important in many parts of Africa because of the expansion of peanut production. In recent years there has, however, been a renewed interest in the crop for cultivation in the arid savannah zones. Bambara groundnut is a popular crop because of its tolerance of drought and the ability to produce a reasonable yield in poor soils.

Constraints associated with Bambara groundnuts production includes, lack of education on the values of the crop, scarcity or in availability of germplasm, pests and diseases. This has contributed to unpopularity and low production of the crop.

Uses.

Bambara groundnut is primarily grown for human consumption, but it has other uses as well. The seeds of the crop make it a complete food, with sufficient and well balanced quantities of carbohydrate, protein, and fats (Oliveira 1976; Linnemann 1987). On average the seeds contain 63% carbohydrate, 19% protein ad 6.5% oil. The gross energy value of Bambara groundnut is said to be greater than that of other common pulses such as cowpea and pigeon pea (FAO, 1982)

In countries such as Angola and Mozambique, boiled salted seeds are often served as appetizers. Commercial canning of Bambara groundnuts in gravy is a successful industry in countries such as Zimbabwe and Ghana.

Bambara groundnuts can be eaten in many ways. Immature pods can be boiled and consumed as snacks. However, at maturity the seeds become harder and require boiling for long time. Seeds can be pounded into flour and used to make stiff porridge. Roasted seeds can be boiled, crushed and eaten as relish. Recently, a trial of Bambara groundnut milk was carried out which compared its flavour and composition with those of milks prepared from cowpea, pigeon pea and soybean (Brough et al, 1993). Bambara groundnut was ranked first and its lighter colour was preferred. This crop may also be used as animal feed. The haulm was found to be palatable (Doku and Karikari 1971a), and the leaves were reported to be rich in nitrogen and phosphorous, and hence suitable for animal grazing (Rassel 1960).

Other than culinary uses, Bambara groundnuts have medical uses as well. The Luo tribe in Kenya use Bambara groundnut for cure of diarrhoea. When water from boiled maize and Bambara groundnut mixture is drunk it treats diarrhoea (Goli, 1991). Leaves can be mixed with those of Lantana trifolia L. and pounded and water added to make a solution which can be used to wash livestock or as an insecticide.

The other virtue of Bambara groundnut is that it is a low-cost, dependable farm resource, which grows in harsh environments where many other crops fail. For Africa, the crop offers various benefits;

an ideal subsistence crop

a good rotation crop

a good backstop for hungry times

a promising commercial resource

It is also among the easier legumes to grow: burying its fruits in the soil, it keeps them safe from the myriad of flying insects that devastate or destroy cowpea, common bean, soybean, and other legumes that heedlessly wave their tastiest parts in the air! Other than requiring open sunlight and light, loose soil within which to bury its pods, Bambara tolerates widely dissimilar substrates, including infertile ones. Some observers swear it "prefers worn-out soils”! The crop thrives in laterite, the reddish acidic soil that is toxic to many crops and is the curse of tropical agriculture.

Morphology

Bambara groundnut is an annual legume with a compact well-developed taproot system with short (up to 20cm long) lateral stems on which leaves are borne. Leaves are trifoliate (± 5cm long). Flowers are typically papilionaceous and are borne in a raceme on long, hairy peduncles, which arise from nodes.

Plants may either be bunch or they may be spreading. Bunch types are usually self-pollinated while the spreading types are usually cross-pollinated by ants. Pods form underground, where they are protected from pests and herbivores. Pods may be about 1.5cm long, round or slightly oval shaped and wrinkled with usually one or sometimes two seeds. Unripe pods are yellowish-white, while mature pods may be yellowish-brown or purple. After fertilization the flower stem elongates and penetrates soil where the fruits develop. The colour of testae varies according to ripeness from light yellow to black, purple and other shades. Seeds are round up to 1.5cm diameter, smooth and hard when dried. Seeds may be black, creamy, brown, red or mottled, with or without hilum colouration.

Genetic resources

The germplasm for bambara groundnut is abundant in Sub-Sahara Africa, as it is grown in every tropical region of the continent. The crop is believed to have originated from northeastern Nigeria and northern Cameroon where its wild relatives have been found. Electrophoretic studies done by Howell (1990) revealed that there was no significant difference between the cultivated genotypes and the wild forms, and it was concluded that the wild plant might just be an escape from the cultivated form. Successful intraspecific hybridization has not yet been reported in the crop, which limits the full exploitation of the available diversity.

The major germplasm collection is held by IITA and has been characterized and evaluated. The large collection of IITA has been gathered from countries across Sub-Sahara Africa and the provenance of the various accessions is indicated in Table 2.

Bambara groundnut seeds are orthodox, and can be stored at temperatures below 0oC. IITA collections are maintained at -20oC, while the collection for distribution is kept in another cold room at 5oC and 30% RH. Most national programmes maintain their collections for medium-term conservation at temperatures above 0oC, and deep freezers are used for conservation of base collections in a number of countries (Goli, 1995).

However, the collections of bambara groundnut available in most national programmes may not reflect all the diversity existing in the respective countries. The crop germplasm is often collected in an opportunistic manner. Germplasm collectors use a collecting mission for a major crop to include sampling of bambara groundnut. Collecting missions primarily devoted to bambara groundnut need to be organized in many countries producing the crop. It has been suggested that where no research programme on the crop exists, an expedition can be organized by the International Bambara Groundnut Network to save those ecotypes that are in the process of extinction.

About the Author

I am a Male Malawian, 49 years of age, currently working as a Lecturer/Researcher in the University of Malawi. I am a keen follower of nature and I am a self-acclaimed naturalist.

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