Conservation of traditional vegetable germplasm in the SADC region

C.N. Nkhoma, G.Y. Mkamanga and T.J. Ruredzo
SADC Plant Genetic Resources Centre, Lusaka, Zambia

Introduction

The SADC Plant Genetic Resources Centre (SPGRC) is a regional programme that coordinates plant genetic resources activities in the Southern African Development Community (SADC) through a network of National Plant Genetic Resources Centres (NPGRCs) and technical guidance of regional crop working groups. The SPGRC maintains the base collection on behalf of the member countries while NPGRCs maintain an active collection of this germplasm for use in the various national programme activities. Whereas in the past vegetable germplasm was only collected during missions that targeted other species, more emphasis will be given to this category of genetic resources with the formation of the Regional Vegetable Crop Working Group in May 1995.

Traditional vegetables of the SADC region

Numerous indigenous plant species that are utilized as vegetables occur throughout the SADC region. These range from wild to cultivated species with varying categories of domestication as outlined below (Okigbo 1990):

· wild and harvested in time of food scarcity
· wild but regularly harvested
· semi-wild, partly protected or harvested from fallow land
· cultivated in mixtures in traditional farming systems
· cultivated in market gardens and specialized horticultural enterprises.

Table 1. Common traditional vegetables of the SADC region.

Species	Common name	Species	Common name
Abelmoschus esculentus	Okra	Dioscorea hirtiflora	-
Amaranthus spp.	Amaranth	Gynandropsis gynandra	Cat's whiskers
Bidens pilosa	Blackjack	Hibiscus spp.	Roselle
Brassica spp.	Mustard	Plectranthus esculentus	Livingstone potato
Celosia spp.	-	Satyrium/Habenaria	Ground orchids
Ceratotheca sesamoides	-	Sesamum spp.	Sesame
Cleome spp.	Cleome	Solarium spp.	African eggplant
Corchorus spp.	Jute	Zanthoxylum chalybeum	-
Cucumis spp.	Cucumbers

Another group of important traditional vegetables are exotic species which were introduced for their fruits, tubers or grain but have been adopted as sources of green leaves. Examples are sweet potato, pumpkin, cassava and beans. Some sweet potato varieties are being cultivated specifically for their leaves and are in fact planted on flat land, unlike tuber sweet potatoes which are planted on mounds. Some indigenous species like cowpeas are often listed as traditional grain legumes. However, their leaves are commonly utilized as vegetables.

History of collecting and conservation

During the IBPGR-funded collecting missions of the late 1970s to mid-1980s, over 1200 accessions of different vegetable species were collected in the SADC region (IBPGR 1984). However, these were largely from Zambia and Zimbabwe and were in fact mainly different species of cucurbits. Table 2 shows vegetable accessions collected with IBPGR support during this period.

Table 2. Vegetable germplasm collections supported by IBPGR in the SADC region.

Species	No. of accessions
Amaranthus spp.	104
Capsicum spp.	57
Corchorus spp.	8
Brassica spp.	27
Cucurbitaceae	927
Hibiscus spp.	15
Solanum spp.	62
Total	1245

These species were never specifically targeted but were collected during multicrop collecting missions that concentrated on the major crops, such as sorghum, millets, maize, cowpea and beans.

During this period there were no suitable storage facilities for long-term conservation in the region. Consequently, most of the subsamples left in the region after collecting were lost or deteriorated over the years.

Conservation at SPGRC

Whereas most of the germplasm collected with the support of IBPGR and other organizations is not currently represented in the SPGRC base collection, indications are that this material is largely available on request from various genebanks throughout the world. Through IPGRI it has been possible to trace most germplasm collected in the region. Consequently SPGRC has embarked on retrieving subsamples of this germplasm on behalf of the NPGRCs.

At present, there are 148 accessions of vegetables in the base collection. Details of species and number of accessions are given in Table 3.

Seed of this germplasm is packed in hermetically sealed bottles and aluminium foil and stored at -18°C. Subsamples are maintained in the active collections at the NPGRCs in the respective countries of origin of the germplasm for routine activities and utilization.

Table 3. Vegetable germplasm in the SPGRC base collection.

Species	No. of accessions
Amaranthus spp.	12
Corchorus spp.	5
Hibiscus spp.	16
Cucumis spp.	5
Cleome spp.	2
Cucurbita spp.	13
Citrullus spp.	94
Zanthoxylum chalybeum	1
Total	148

Conservation at the NPGRCs

The NPGRCs are currently building up their stocks of vegetable germplasm in some SADC countries. Table 4 shows details of vegetable germplasm maintained at the NPGRCs. However, some of the germplasm may still be maintained by the various national horticultural and vegetable research programmes. Such germplasm not duplicated at the NPGRCs is not reflected in this table.

Table 4. Vegetable germplasm at the NPGRCs active collections.

Genus	Country
	Botswana	Malawi	Namibia	Swaziland	Tanzania	Zambia	Total
Abelmoschus	-	-	-	-	-	119	119
Amaranthus	2	-	-	11	-	88	101
Bidens	-	-	-	-	-	1	1
Brassica	-	-	-	-	-	1	1
Citrullus	110	-	21	-	1	83	215
Cleome	15	-	-	-	1	2	18
Corchorus	10	-	-	3	-	4	17
Cucumis	17	-	22	-	1	20	60
Cucurbita	8	-	-	-	28	252	288
Hibiscus	-	-	1	-	2	93	96
Sesamum	7	6	7	-	8	37	65
Solarium	-	-	1	-	-	4	5
Total	169	6	52	14	41	704	986

Note: Data for Angola, Lesotho, Mozambique, South Africa and Zimbabwe are not currently available.

Regional Vegetable Crop Working Group

The SPGRC is at the moment facilitating four Regional Crop Working Groups (RCWGs): Cereals and Food Legumes; In Situ and Underutilized Plants; Forage and Fodder, and Vegetables. The RCWGs are each made up of five scientists nominated in their personal capacity from the SADC member States who are working in National Agricultural Research Systems (NARS) as specialists in their mandate species. Researchers from the SADC regional programmes, projects and IARCs are coopted into the RCWGs. These RCWGs complement the scientific expertise that exists at SPGRC. The main function of the RCWGs is to make recommendations to the Director of SPGRC on: strategies; priorities for plant species to be collected and conserved; priorities for plant species and areas of in situ conservation; guidelines for acceptance of material, standards for seed quantity and quality, methods and techniques for regeneration and multiplication of accessions in order to ensure genetic integrity.

At its first meeting on 18 May 1995, the Regional Vegetable Crop Working Group made the following recommendations which will be presented to the Board of SPGRC in October 1995:

1. Members of the Vegetable Crop Working Group (VCWG) will assemble lists of utilized vegetables from their countries and/or organizations and submit them to SPGRC for compilation before the next meeting.

2. The SPGRC will circulate the compiled list among all the NPGRCs to get an indication of which species are utilized in the different countries.

3. The SPGRC should solicit literature on vegetables from member States and IARCs.

4. The SPGRC should facilitate the systematic collection of pertinent data and information on the status of indigenous vegetable research including staffing and facilities.

5. The VCWG listed the priorities for collecting and ex situ conservation as follows:

· species of regional and/or national economic importance
· species facing danger of genetic erosion
· indigenous species
· landraces of exotic species
· species on the mandate list of VCWG.

6. The VCWG recommended that all material to be included in the collection should be accompanied by passport data.

7. The VCWG will compile standards to be used at SPGRC for the conservation of indigenous vegetable germplasm. Literature should be collected and sent to SPGRC which should compile and send these to the VCWG members before the next meeting to facilitate the compilation of these standards.

8. SPGRC should encourage relevant institutions such as IPGRI, FAO, SADC-AVRDC, NARS and NGOs to conduct socioeconomic surveys on the use of indigenous vegetables in the SADC region.

Prospects for the future

Some member States have in recent years initiated programmes that are resulting in improved varieties of vegetables such as Amaranthus and Solanum macrocarpon. These programmes will require a wider pool of genetic material that should be collected, characterized and utilized as and when the need arises. With the formation of the Regional Vegetable Crop Working Group, collecting and conservation of traditional vegetable germplasm will increase in the region.

Table 5. SPGRC Vegetable Regional Crop Working Group Mandate list for conservation.

Species	Common name	Indigenous/Exotic	Status
Abelmoschus esculentus	Okra	I	P
Abutilon cabrae	-	I	-
Acacia arabica	-	I	-
Adansonia digitata	Baobab	I	-
Albizia spp.	Rain tree	I	-
Allium ascalonicum	Shallot	E	P
A. schoenoprasum	Chives	E	-
Amaranthus hybridus	Amaranth	I	P
A. viridis	Amaranth	I	P
Amaranthus spp.	Amaranth	I	P
Apium graveolens	Celery	E	-
Asparagus spp.	Asparagus	I	-
Basella alba	-	E	-
B. rubra	-	E	-
Bauhinia esculenta	-	I	-
Bidens bipinnata	-	I	-
B. pilosa	Blackjack	I	-
Brassica juncea	Mustard	I	P
Cajanus cajan	Pigeon pea	I	-
Canavalia ensiformis	Jackbean	E	-
Capsicum frutescens	Pepper	E	P
Ceiba pentandra	-		-
Celosia argentea	-		P
Ceratotheca sesamoides	-		P
Chenopodium murale	-		P
Cholophora excelsa	-		-
Cissus spp.	-		-
Cleome hirta	-		P
C. monophylla	-		P
Colocasia esculenta	Taro	E	P
Colocynthis vulgaris	Bitter lemon		-
Commelina diffusa	-		-
Corchorus aestuans	-		P
C. tridens	-		P
C. olitorius	-		P
Crassocephalum biafrae	-		-
C. crepidioides	-		-
Croton mubange	-		-
Cucurbita maxima	Pumpkin	E	P
Cyperus esculentus	Nutsedge		-
Dracaena spp.	-		-
Ficus spp.	Fig		-
Grewia spp.	-		-
Gynandropsis pentaphylla	-		P
Hibiscus sabdariffa	Roselle		P
H. rosasinensis	Hibiscus		-
Ipomoea batatas	Sweet potato	E	P
Lactuca taracifolia	-		-
Lagenaria siceraria	Gourd		P
Luffa cylindrica	Luffa		P
Manihot esculenta	Cassava	E	P
Mentha spp.	Mint	E	-
Ocimum viride	Fever plant	I	-
Phaseolus vulgaris	French bean	E	P
Plectranthus esculentus	Livingstone potato	I	P
Polygonum spp.		I	-
Portulaca oleracea	Purslane	I	-
Ricinus communis	Castor	E	-
Rumex bequaertii		I	-
Saccharum officinarium	Sugarcane	E	-
Sesamum radiatum	Sesame	I	P
Sesbania aegyptiaca	Sesbania	I	-
Solanum aethiopium	African eggplant	I	P
S. incanum	-	I	-
S. macrocarpon	African eggplant	I	P
S. melongena	Aubergine	E	-
S. nigrum	-	I	P
S. nodiflorum	-	I	-
Telfairia pedata	Fluted pumpkin	E	P
Trichosanthes cucumerina	Snake pumpkin	E	-
Typha spp.	-	I	-
Vernonia anygdelina	-	E	-
Vigna subterranea	Bambara	I	-
V. unguiculata	Cowpea	I	P
Zea mays	Maize	E	-

Note: Under "Status", P = priority

IBPGR. 1984. Collection of Crop Germplasm. The First Ten Years 1974-1984. IBPGR, Rome.

Lewis, G. 1974. The Preliminary Collection of the Useful Wild Plants of Zambia.

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.

Williamson, J. 1975. Useful Plants of Malawi. Revised. University of Malawi, Zomba.