Jean Hanson and John R. Lazier
Forage Agronomy Group
International Livestock Centre for Africa
P.O. Box 5689, Addis Ababa, Ethiopia
Introduction
The germplasm collection
Improving the collection
Storage of material
Germplasm data
How to select germplasm from the genebank
What germplasm to select
References
Abstract
The International Livestock Centre for Africa (ILCA) holds a large collection of forage germplasm of legumes, grasses and browse in controlled storage conditions at its headquarters in Addis Ababa. The germplasm collection is a major responsibility of the forage agronomy programme at ILCA. The forage germplasm available and its storage is described. The types of data recorded about each accession and how to use these data to select suitable germplasm for screening activities is explained.
The success of a forage research or development and improvement programme is usually dependent on the availability of adapted, productive and appropriate forage germplasm for selection of promising lines. In most African countries such germplasm has been difficult to obtain in the past because the sources were in institutions with no particular interest in or responsibility for forage development in Africa.
It was in recognition of this serious impediment to forage development in Africa that the Forage Agronomy Group (FLAG) at ILCA Headquarters in Addis Ababa established a forage genetic resources collection as a service to collaborators and other research workers in national programmes in Africa and for forage development work in ILCA programmes. This collection was begun in 1982 and has grown over the past five years until it now contains 9166 accessions of forage species, including legumes, grasses and browse.
The maintenance of such a large and varied collection is now a major responsibility of FLAG, which has accepted the international responsibility to store this germplasm and make it freely available for research and development. All original material is being duplicated in other forage genebanks for security under the IBPGR global network of base collections (Hanson et al., 1984).
The germplasm collection is composed of about 75% legumes and 10% each of grasses and browse with 111 genera and 341 species represented in the collection. The major part of the collection is made up of experimental lines of germplasm which were either acquired from other institutions or original collections of forages from various countries in Africa, including Ethiopia, Kenya, Rwanda, Niger, Burundi, Eastern Zaire, Mali and Tanzania. Due to FLAG being located in Ethiopia and the resulting ease and economy of collection there, the largest number of ILCA collected accessions are Ethiopian, and they constitute 30% of the total collection. FLAG collecting missions in the other countries have contributed a further 10% of the accessions. Commercial lines of legumes and grasses make up about 5% of the collection and are held as a service to users who wish to test commercial lines in small quantities for preliminary evaluation.
Due to the great range of environments in ILCA's mandate region and due to the centre of diversity of many important legumes lying outside Africa, primarily in South and Central America and Asia, FLAG has made considerable efforts to acquire representative sets of germplasm of potential value for development in Africa from institutes with collections from these regions. Almost 20% of the collections were obtained from the Centro International de Agricultura Tropical (CIAT) based at Cali in Colombia which has a large collection of legume germplasm from Central and South America, the main centre of diversity of forage legumes. FLAG has strong co-operative links with the staff of the tropical pastures programme at CIAT, and in the past CIAT and ILCA have held joint collection missions for forages in Africa. Another major donor of germplasm has been the Division of Tropical Crops and Pastures (CSIRO) based in Queensland, Australia from whom ILCA has received almost 10% of its germplasm. The remaining accessions have been acquired in smaller numbers from other research organizations, from individual scientists or as duplicates of materials held by ILCA's field programmes in Nigeria and Mali.
Despite the number of accessions already in the genebank, there is much variation in both exotic and native African species of recognised forage value which is not represented in the collection. In addition, there are more than 50 of the 111 genera held by the genebank which are as yet only represented by very few accessions. These genera cannot be usefully tested with such a narrow range of material.
African germplasm of forage potential has been little explored, and legumes, grasses and browse can be profitably collected. Concentration of collection activities in individual species and genera has captured tremendous genetic variation, for example in the East African highlands, Trifolium species (collected by ILCA), Brachiaria decumbens (collected by ILCA-CIAT) and Panicum maximum (collected by ORSTOM).
Genera worthy of attention in Africa due to their diversity, include among others the legumes Macrotyloma, Lablab, Aeschynomene, Crotalaria, the browse Sesbania, Erythrina and Acacia and many species of grasses, including Digitaria, Pennisetum, Cynodon and Chloris.
Forage species are also needed for development for specific African environments. For example there are few truly promising legumes for semi-arid and acid soil conditions. Browse germplasm is very limited for acid soils and high altitudes. Such germplasm may be obtainable from other genebanks, or collections may have to be undertaken within or outside of Africa.
There is an urgent need to collect and preserve genetic variation in species with genetic potential from areas subject to rapidly increasing population pressures before they are lost due to the resulting drastic environmental changes. Genetic erosion in forages and other wild species is occurring at a rapid rate in many areas, and timely action to collect is essential if valuable germplasm is not to be lost.
Due to the small amount of forage germplasm collection done to date in Africa, almost any well planned collection is bound to produce new and substantial variation. Collecting missions require considerable forward planning to be successful. The target species, area of collection and time of year must be defined in order to optimise the number of accessions obtained. In 1987 FLAG has planned two collecting missions. One is genus-specific to collect mainly Sesbania species in Tanzania during July to August, although other genera of interest will also be collected if time allows. The other is a more general Ethiopian browse collection mission, which will probably be split into several short missions beginning in May to cover the seeding period of many species.
The material collected must be conserved in an appropriate manner so that it remains available for distribution and is not lost or merely stored without being utilised. The easiest storage method is in a seed genebank. ILCA has recently installed new drying and cold rooms to process and store seeds under conditions in line with the IBPGR recommendations for the storage of seeds in genebanks (IBPGR, 1985). Seeds are first dried to between 3-7% moisture content in a dehumidified drying room, which operates at 15°C and 20% relative humidity. Under these conditions small seeds reach the required moisture content within one week while larger seeds take up to two weeks. When the seeds are dry they are packed in moisture-proof laminated aluminium foil bags which are carefully labelled and placed into store. ILCA has two types of germplasm storage. The active collection, composed of larger seed samples for distribution, is stored in a cold room at 5°C. The base collection is for security storage only and is stored in deep freezers at -20°C.
Another method of conservation is to maintain plants in field genebanks. ILCA has a field genebank in the Rift Valley where a large collection of Brachiaria species and some other grasses are planted out. Many grass species rarely produce viable seeds and at ILCA maintenance in plots is the only feasible way to conserve these species. In vitro genebanks where meristem cultures are maintained in test tubes under controlled environmental conditions, are an alternative method of storage of species which do not readily produce seeds. FLAG is already culturing meristems of Brachiaria species for distribution, and work will begin later this year on methods of culturing other grass genera and the development of in vitro storage procedures.
In order that germplasm can be efficiently utilised, basic information should be available about each accession, thus allowing selection of potentially adapted materials for specific ecological zones. At collection, as much useful field data as possible is recorded about each accession and the site where it was collected. In genetic resources terms this data is known as passport data. A standard collecting form is used to record the data (Lazier, 1985) which is then entered into the computerised database. More data is obtained from references and analyses of soil samples. Further identification of herbarium specimens may be necessary. The database which ILCA uses has been made as comprehensive as is practical in order that a maximal amount of data is available to researchers.
Another set of data known as preliminary characterisation data is recorded when the material is first grown in the field. This is, in general, observation data on morphology and adaptation obtained from a small number of plants in unreplicated plots. Further evaluation in replicated strip trials provides agronomic data which allows selection of promising material for multi-site evaluation trials in national programmes.
To date only the passport data has been entered into the germplasm database, but it is envisaged that a supplementary database of agronomic characters will also be established in the development of the genebank documentation system. The computer is a valuable tool in germplasm work because it allows rapid selection of subsets of accessions by query on specific fields, preparation of germplasm catalogues and lists of passport data and manipulation of data.
With such a wide array of germplasm available, the user may find it very difficult to select accessions for evaluation. The forage agronomists in FLAG can provide advice on promising materials to test, but selection is also possible directly by the user. FLAG publishes a germplasm catalogue which is updated at regular intervals (ILCA, 1985). This lists all accessions available in the genebank in three ecologically organised volumes: tropical lowland, temperate/Mediterranean and tropical highland. The accessions in each volume are divided into annual and perennial legumes and grasses and presented in alphabetic and accession number order. A section on browse species is included in the tropical lowland germplasm catalogue, since the majority of the multi-purpose tree species are of tropical origin. As our collection expands with the addition of more temperate materials, sections on browse may be added to other catalogues.
Since the catalogue cannot contain all useful data on an accession because of the amount of data available and large number of accessions, only the fields most useful for selection of appropriate germplasm for evaluation were included in the catalogue. This includes collection site data such as geographic location, rainfall, soil type and pH and other identification numbers of each accession.
The catalogue can be used to select annual or perennial accessions of species of interest which were collected from areas of similar environment to the trial site. Users can then fill the ILCA numbers of selected lines onto an ILCA seed request form and submit this to FLAG.
Germplasm is freely available from the FLAG genebank in small experimental quantities of a few seeds to a few grams. The recipients must multiply seeds of any promising material for use in subsequent experiments themselves. In return for the seeds, recipients are requested to provide the genebank with information on the performance of the lines tested, in order that the genebank can provide adapted germplasm for similar environments with greater assurance, thus providing a better service and considerable savings in time and labour.
It is obvious that with the wide range of environments encountered in sub-Saharan Africa, that sets of adapted germplasm must be developed for different ecological situations. FLAG currently evaluates its germplasm in four major environments. Three are in Ethiopia: tropical sub-humid, mid-altitude on acid soils, tropical semihumid highland. More recently evaluation was commenced on tropical sub-humid lowland acid soils in Nigeria. Over the last four years a series of trials have been carried out in the Ethiopian sites and promising experimental materials have been selected for each of these environments. These are then planted in larger plots to see if they maintain their comparative advantage compared to commercial or previously available lines and to obtain sufficient seeds for larger scale trials. FLAG is building up its stocks of seeds of promising accessions so that they can go into wider testing in national programmes in 1988. Collaboration with national research centres through PANESA is the next important step in the development of promising forage germplasm for utilisation in animal production systems in the region.
Hanson, J., Williams, J.T. and Freund, R. 1984. Institutes conserving crop germplasm: the IBPGR global network of genebanks. IBPGR, Rome.
IBPGR. 1985. IBPGR Advisory Committee on seed storage. Report of the third meeting. IBPGR, Rome.
ILCA. 1985. ILCA forage germplasm catalogue 1985. Vols 1-3. ILCA, Addis Ababa, Ethiopia.
Lazier, J.R. 1985. Theory and practice in forage germplasm collection. In: J.A. Kategile (ed.), Pasture improvement and research in Eastern and southern Africa. IDRC-237c.
