Conservation and use of traditional vegetables from woody forest species in southeastern Nigeria

J.C. Okafor
FAME Agricultural Centre, Enugu, Nigeria

Abstract

In Nigeria, where the diet is dominated by starchy staple foods, traditional vegetables are essential sources of proteins, vitamins, minerals and amino acids. The majority of these vegetables are still being harvested from the wild. Two research projects sponsored by the World-Wide Fund for Nature (WWF) are investigating the prospects of conservation and its attendant problems as perceived by the participating farmers. It is concluded that various inputs and education are necessary to promote the conservation and sustainable utilization of traditional vegetables in the region.

Introduction

In Nigeria, as in other tropical countries of Africa where the daily diet is dominated by starchy staple foods, vegetables are the cheapest and most readily available sources of important proteins, vitamins, minerals and essential amino acids (Okafor 1983).

The southeastern region of Nigeria, which is covered in this presentation, lies between latitudes 4°20' and 7°00'N and longitudes 5°25' and 9°35'E. It is bounded on the east by the Republic of Cameroon, on the south by the Atlantic Ocean (or the Bight of Bonny), on the west by the River Niger and on the north by Kogi, Benue and Taraba States. The zone comprises seven of Nigeria's 30 states, namely Enugu, Anambra, Imo, Abia, Akwa Ibom, Cross River and Rivers States. The climate and vegetation of the area are described in Keay (1959), Agboola (1979) and NEST (1991).

The prevailing climate conditions are high rainfall, constantly high temperatures, high atmospheric humidities and precipitation usually exceeding evapotranspiration for more than half the year. The vegetation types are mangrove and freshwater swamp communities, rainforest, forest/savanna mosaic and derived savanna zone. These vegetation subtypes all belong to the forest zone (Okafor 1979).

The farming systems prevailing in the region are dominated by yam/root crops/plantain, with oil palm bush and indigenous trees of nutritional, economic, medicinal and cultural importance. These trees are sources of fruits and leaves which are mostly harvested from wild or semi-wild and rarely cultivated plants. Quite often fruits and leaves are also obtained from wild and cultivated non-woody (herbaceous) plants.

This paper will focus on the conservation and use of traditional vegetables obtained mainly from woody forest species, based on the result of two projects:

· 'Development and utilization of fast disappearing and underutilized edible wood forest species of south-eastern Nigeria'

· 'Monitoring and evaluation of biodiversity conservation programme in southeastern Nigeria'.

The aims and objectives of the first project on development and utilization of edible woody forest species include (Okafor et al. 1996):

· to provide basic data and information necessary for sustainable commercial exploitation of threatened species

· to develop suitable propagation and field-management techniques, as well as to provide planting materials

· to involve local participation in conservation programmes and generate employment in the project area.

· to examine, highlight and document local perception, knowledge and problems of conservation of threatened rainforest species and apply such information and knowledge in the conservation, sustainable development and rational utilization of tropical biodiversity

· to determine the economic, social and ecological values and contributions of tropical rainforest species to the welfare of local people and thus demonstrate the pressing and compelling need for their conservation

· to involve local people in the development and practice of conservation programmes with emphasis on their interest, experience, socioeconomic and cultural backgrounds and setting.

· nursery establishment by farmers

· periodic monitoring visits to the 60 farmers in the three project centres, namely Ntueke (Imo State), Ukpor (Anambra State) and Nike (Enugu State) for supervision and compilation of conservation data and records

· synthesis of monthly records of conservation activities by farmers

· group-structured interviews with participating farmers and other interested individuals, using questionnaire forms, to elicit information on problems and prospects of conservation in the zone

· periodic workshops and seminars at centre and regional levels, to examine problems, prospects and also to introduce conservation training to participating farmers.

Results

Study species

Out of the 19 species which were selected for the study, on account of their great potential, prevailing neglect and increasing threat of genetic erosion due to deforestation pressures (Okafor et al. 1996), nine are important sources of traditional vegetables (see Table 1). The culinary use of these vegetables is also indicated in the table.

Apart from these species, other vegetable plants which are grown at FAME Agricultural Centre include Afzelia bella, Ficus sur, E. thonningii, Ceiba pentandra, Moringa oleifera, Ocimum gratissimum and Vitex doniana.

In addition to the list of vegetable species studied and/or grown at FAME Agricultural Centre as mentioned above, several other forest species are sources of traditional vegetables in the southeastern zone (Okafor 1989, 1990). Most of these vegetables are mostly harvested from the wild. They include leafy vegetables such as Beilshmedia mannii, Gnetum spp., Gongronema latifolium, Heinsia crinata (atama), Myrinthus arboreus (ujuju), Lasianthera africana (editan), Piper umbellatum and Talinum triangulare (water leaf). Flowers of Glyphaea brevis, Kigelia africana, Moringa oleifera and Bombax sp. are used as vegetables to a limited extent. Similarly, leaves of timber species such as Milicia excelsa and Albizia zygia are sometimes used as a vegetable.

Table 1. List of vegetable species studied.

Botanical name	Family	Vernacular name	Uses
Trees
Pterocarpus mildbreadii	Papilionoideae	Oha	Leafy vegetable in soups
P. santalinoides	Papilionoideae	Nturukpa	Leafy vegetable in soups
P. soyauxii	Papilionoideae	Oha	Leafy vegetable in soups
Shrubs
Dioscoreophyllum cumminsii	Menispermaceae	Utobili	Tuber used for thickening soups
Gnetum africanum	Gnetaceae	Okazi/Afang	Leaves eaten raw in salads; cooked in soups
G. buchholzianum	Gnetaceae	Okazi/Afang	Leaves eaten raw in salads, also cooked in soups
Gongronema latifolium	Asclepiadaceae	Utazi	Leaves used raw in salads and to flavour meat preparations and fresh fish pepper soups
Piper guineense	Piperaceae	Uziza	Leaves used as vegetable pepper in soups
Vernonia amygdalina	Compositae	Onugbu	Leaves used as vegetable in soups after washing to remove bitterness

Chemical analysis of traditional leafy vegetables

The results of proximate analysis of leaves of important traditional vegetables show that they are valuable sources of minerals, protein and fats/oil (Table 2). It is thus noted that Gnetum africanum, Gongronema latifolium, Piper guineense and Vernonia amygdalina are good sources of minerals (Na, K, Ca, Mg and Fe). The fat contents of G. latifolium, G. africanum and V. amygdalina are significant (18.77, 14.20 and 4.50%, respectively).

These woody leafy vegetables are available at strategic periods in the year, namely the dry season, when the conventional cultivated vegetables are scarce. They therefore contribute significantly to the food security and nutritional well-being of the local people in the region.

Nursery practices

Germination. Germination trials were conducted on six vegetable species. Table 3 shows the optimal germination conditions for each species, except G. africanum, which failed to germinate.

Stem cuttings. Propagation by stem cuttings was successful for G. latifolium, Pterocarpus santaliniodes, Pterocarpus soyauxii and V. amygdalina in various media (topsoil, sawdust, river sand) and a mixture of these together with charcoal. It was found that juvenile cuttings were more successful in P. santalinoides and P. soyauxii, while adult cuttings were preferable for the climber G. latifolium. Both adult and juvenile cuttings were successful in V. amygdalina.

Technique for "dwarfing" Pterocarpus soyauxii. Bending seedlings at an angle of 45° produced multiple shoot formation and bushy growth habit, which is useful for rendering harvesting of vegetables easier.

Table 2. Chemical analysis of some leafy vegetables of southeastern Nigeria.

Scientific name	Moisture (% fresh)	Ash (% dry)	Oil (%)	Protein (%)	Na (ppm)	K (ppm)	Ca (ppm)	Mg (ppm)	Fe (ppm)	Zn (ppm)	Cu (ppm)	Mn	P
Gnetum africanum	37.39	4.72	14.20	10.18	26	126	28.35	14.75	5.23	0.49	0.06	-	-
Gongronema latifolium	71.14	10.94	18.77	62.66	58	336	20.75	56.00	8.17	0.90	0.12	-	-
Myrianthus arboreus	75.52	9.83	1.34†	20.01	-	-	1.132‡	-	0.036‡	-	-	2.134‡	2.543‡
Piper guineense	78.58	15.56	9.30	18.54	35	320	7.11	147.00	6.12	2.05	0.15	-	-
Pterocarpus soyauxii	74.69	2.83	3.60	3.84	1.8	11.1	19.37	35.5	3.79	0.84	0.21	-	-
Vernonia amygdalina	79.67	10.13	4.50	23.24	46	304	40.00	58.00	4.72	0.81	0.10	-	-
Vitex doniana	84.05	7.61	1.10†	22.07	-	-	0.185‡	-	0.045‡	-	-	0.444‡	6.136‡

^† = fat.
^‡ Determined as % of dry matter (not as ppm).
Sources: Okolo 1987; Okafor et al. 1996.

Species	Days to germinate	Pretreatment required	% germination
Dioscoreophyllum cummunsii	68	Depulp and sun-dry for 1 day	69.6
Gongronema latifolium	6	None	81.6
Piper guineense	22	Depulp and air-dry in shade	42.6
Pterocarpus soyauxii	7	Remove pericarp and soak overnight in cold water	86
Vernonia amygdalina	8	None	89

Table 4. Farmers' involvement in raising of vegetable species in southeastern Nigeria, 1994-95: number of farmers involved^† and % involvement at three study sites.

	Ntueke		Ukpor		Nike		All	centres
	no.	%	no.	%	no.	%	no.	%
Gnetum spp.	13	43	8	40	1	10	22	37
Gongronema latifolium	15	50	9	45	1	10	25	42
Piper guineense	9	30	8	40	0	0	17	28
Pterocarpus soyauxii	4	13	5	25	2	20	11	18
Pterocarpus santalinoides	3	10	0	0	0	0	3	5

^† Total number of farmers at Ntueke=30, at Ukpor=20, at Nike=10.

		Farmers in Ntueke					Farmers in Ukpor				Farmers in Nike
S no.	Problem	1	2	3	4	5	1	2	3	4	1	2	3	% of farmers
1	Grazing animals	×	×	×	-	-	×	×	×	-	×	×	-	66.7
2	Lack of cash	×	×	×	×	×	×	×	×	×	×	×	-	91.7
3	Lack of knowledge on germination/growing techniques of species	×	-	×	-	-	-	-	-	-	-	×	-	25.0
4	Lack of knowledge on preservation, storage and utilization techniques	×	×	-	-	-	-	-	-	-	×	×	×	41.7
5	Lack of labour	×	×	×	×	-	×	×	×	×	-	-	-	66.7
6	Lack of seeds and planting material	×	×	×	×	-	×	×	×	×	×	×	-	83.3
7	Lack of water	×	×	×	×	×	×	-	-	×	-	-	-	58.3
8	Land	×	-	-	-	×	×	×	-	-	×	-	×	50.0
9	Seedling mortality and survival	×	×	×	×	-	×	×	×	×	×	×	×	91.7
10	Working tools and materials	×	×	-	×	×	×	×	×	×	-	-	-	66.7

× = positive response.

The 60 participating farmers at the three project centres showed keen interest in the nursery development of vegetable and other edible species. Six vegetable species were grown by them (see Table 4). However, apart from G. latifolium, less than 50% of the farmers cultivated the listed species, for various reasons. The constraints or problems encountered by the farmers are shown in Table 5. These include: (1) lack of various inputs, such as cash, labour, planting materials, water, equipment; (2) lack of knowledge of, and skill in, propagation; (3) pests; (4) mortality of seedlings, etc.

Similarly, Table 6 indicates the prospects and usefulness of conservation of biodiversity, including vegetables, as perceived by the farmers. The importance of different species as sources of food, medicine, cash income and for reasons of cultural observance is clear.

Non-food uses of traditional vegetables

The following vegetable species are reported to have medicinal properties:

Gnetum spp.	Treatment of piles and high blood pressure
Gongronema latifolium	Source of iron, promotes pregnancy, treatment of diabetes.
Moringa oleifera	Relieves frontal headache
Ocimum gratissumum	Eye drop, treatment of stomach problems, diarrhoea and piles
Piper guineense	Promotes pregnancy
Pterocarpus santalinoides	Treatment of diarrhoea, high blood pressure (in conjunction with P. soyauxii and Solanum macrocarpum leaves)
Vernonia amygdalina	Local iodine for wounds, treatment of diabetes
Vitex doniana	Treatment of diarrhoea and stomach pains

Export promotion

Bitters extracted from leafy vegetables V. amygdalina and G. latifolium could be explored for export. These leaves also have potential in beer brewing.

Conclusions and recommendation

The following conclusions can be drawn from the results of the projects described here:

1. Despite the dietary and nutritional importance of traditional vegetables in southeastern Nigeria, several of the species are still only harvested from the wild, including Gnetum spp., Heinsia crinata, Lasianthera africana, among others. They are sources of cash income.

2. Intensive harvesting, including destructive methods such as uprooting, in order to maximize cash returns from such vegetables (e.g. Gnetum), is contributing to increasing threat of genetic erosion of such species. There is a need for education to address this situation.

3. Simple techniques of propagation as developed by the projects are useful in conserving and popularizing traditional vegetables.

4. Conservation efforts are associated with several constraints, which are clearly perceived by farmers themselves. Such problems must be addressed to enhance local participation in conservation.

5. Apart from their food value, traditional vegetables are useful for other purposes, such as medicine, cash income and in cultural observance. These benefits can contribute to the conservation of these species.

		No. of farmers at Ntueke					No. of farmers at Ukpor				No. of farmers at Nike			Total no. for codes†
S no.	Prospects	1	2	3	4	5	1	2	3	4	1	2	3	1	2	3
1	Gnetum spp. (Okazi)
	Food	1	3	1	2	3	2	3	2	2	1	1	1	5	4	3
	Cash	3	1	2	1	2	1	1	1	1	1	1	1	9	2	1
	Medicine	-	-	3	-	1	3	-	3	3	-	-	2	1	1	4
	Culture	-	-	-	-	-	3	-	3	3	3	3	-	-	-	5
2	Vernonia amygdalina (Bitter leaf/Onugbu)
	Food	1	3	1	2	2	2	1	2	2	1	1	1	6	5	1
	Cash	2	2	1	2	2	2	1	2	2	1	1	1	5	7	-
	Medicine	3	-	1	1	1	1	1	1	1	1	1	-	9	-	1
	Culture	-	-	-	-	-	-	-	-	-	1	1	-	2	-	-
3	Pterocarpus spp. (Ora)
	Food	1	2	1	1	2	2	1	2	2	1	1	1	7	5	-
	Cash	-	2	2	1	2	1	1	1	1	1	1	1	8	3	-
	Medicine	-	-	3	-	-	-	-	-	-	-	-	-	-	-	1
	Culture	3	-	-	3	-	2	1	1	2	-	-	-	2	2	2
4	Gongronema latifolium (Utazi)
	Food	3	3	1	-	-	2	1	2	2	1	1	1	5	3	2
	Cash	-	1	2	2	2	2	1	2	2	1	2	1	4	7	-
	Medicine	1	-	1	1	1	1	1	1	1	-	1	2	9	1	-
	Culture	-	-	-	-	-	3	-	3	3	3	-	-	-	-	4
5	Pterocarpus soyauxii (Uturukpa)
	Food	1	2	1	1	2	2	1	2	2	1	1	1	7	5	-
	Cash	-	2	2	1	2	1	1	1	1	1	1	1	8	3	-
	Medicine	-	-	3	-	-	-	-	-	-	-	-	-	-	-	1
	Culture	3	-	-	3	-	2	1	1	2	-	-	-	2	2	2
6	Piper guineense (Uziza)
	Food	-	2	1	-	2	2	1	2	2	1	-	1	4	5	-
	Cash	-	2	1	3	2	1	1	1	1	1	-	1	7	2	1
	Medicine	1	-	1	3	-	1	1	1	1	-	3	1	8	-	1
	Culture	-	-	-	-	-	1	-	1	1	-	2	-	3	1	-

^† Codes: 1 = high use; 2 = moderate use; 3 = low use; used in rating by farmers.

References

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Keay, R.W.J. 1959. An Outline of Nigerian Vegetation. Federal Department of Forestry Research, Federal Ministry of Information, Lagos.

NEST. 1991. Nigeria's Threatened Environment. A National Profile. Nigerian Environmental Study/Action Team (NEST), Ibadan.

Okafor, J.C. 1979. Edible indigenous woody plants in the rural economy of the Nigerian forest zone. In The Nigerian Rainforest Ecosystem (D.U.U. Okali, ed.). Proceedings of M.A.B. Workshop on the Nigerian Rainforest Ecosystem. University of Ibadan, Nigeria.

Okafor, J.C. 1983. Horticulturally promising indigenous wild plant species of the Nigerian forest zone. Acta Hort. 123:165-176.

Okafor, J.C. 1989. Agroforestry aspects. Appendix 2 of plan for Developing the Cross River National Park, and its support zone, Oban Division. WWF, Godalming, UK.

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Okafor, J.C., H.C. Okolo and M.A.N. Ejiofor. 1996. Strategies for enhancement of utilization potential of edible woody forest species of south-eastern Nigeria. Pp. 684-695 in The Biodiversity of African Plants (L.J.G. van der Maesen et al., eds.). Kluwer, The Netherlands.