by
C.E. Hughes
Oxford Forestry Institute
South Parks Road
Oxford OX1 3RB
UNITED KINGDOM
Following a collaborative initiative between CATIE, the University of Hawaii, the Visayas State College of Agriculture in the Philippines and the Oxford Forestry Institute in 1983 (Glover and Brewbaker, 1984) OFI, in collaboration with nine Latin American countries, completed rangewide seed collection of Gliricidia. These collections, assembled over four seasons from 1983–1986, sampled over 2400 individuals from 30 provenances in eight countries (see Map 1). Basic biological information on taxonomy, distribution, ecological amplitude, phenology, breeding systems and patterns of variation which formed the basis for sampling, will be reported elsewhere (Hughes, in press). Collections were designed to sample as widely as possible over the complete range of latitude and altitude, including the extremes of climate and soil encountered within the natural distribution. In addition, a number of land races from other parts of Central America and northern South America were included and it is anticipated that seed of material selected for local adaptability in Nigeria and land race material from Thailand will also be available. The sampling of a broad genetic base will allow flexibility in future selection of provenances/land races to be introduced at a larger scale, and their subsequent improvement.
Distribution of experimental quantities of the seed collected of Gliricidia sepium for international trials started in January 1987, and has now gone to some 155 trials in 53 countries leaving seed stocks depleted.
1 Manuscript received January 1987.
BACKGROUND
Gliricidia sepium (Jacq.) Walp. is a medium-sized, thornless, leguminous tree native to Mexico and Central America. In the past it has been introduced to many tropical areas and is cultivated and sometimes naturalized in northern South America, the Caribbean, Hawaii, west Africa, sporadically in eastern and southern Africa, India, Sri Lanka, South-East Asia (including Thailand, the Philippines and Indonesia) and Australia. More recently Gliricidia was included as one of the 26 dry zone multipurpose tree species selected for species elimination trials by OFI (see Hughes and Styles, 1984) and seed has now been distributed to some 145 trials in 42 countries (Hugues, 1986).
In Central America and Mexico Gliricidia is one of the most common trees occurring in areas below 1500 m elevation sometimes in great abundance, yet its native distribution is not clearly known. Meticulous exploration of the region has now allowed a tentative distribution map to be drawn up (Map 1). While the literature suggests that Gliricidia produces a very wide range of useful products including fuelwood, fodder, poles, green manure and bee forage (Falvey, 1982, NAS, 1980) and can be used in a variety of production systems from pure plantations to intimate agroforestry mixtures, its benefits and usefulness are not always clearly perceived by the users. Gliricidia is extremely easy to establish, cultivate and manage and on many sites is fast growing and therefore particularly well suited for use by farmers in agroforestry or other farm situations, making Gliricidia a valuable alternative e.g. to Leucaena leucocephala; it is showing particular promise for green manure production in alley-cropping systems (Agboola et al., 1981). Gliricidia grows well on a wide range of soils from pure sands to stony freely drained regosols and deep black vertisols in the pH range 5.5–7.0. It is apparently moderately salt tolerant but will not grow where waterlogging is prevalent. In the natural distribution rainfall ranges from 600 to 3,500 mm with the majority of sites around 1,000 mm and a 5 to 6 month dry season. Although Gliricidia can survive with rainfall as low as 400 mm, dry season dieback and slow growth are apparent and best results will be obtained in areas with more than 600 mm. Gliricidia is frost intolerant but can withstand fires by resprouting.
Gliricidia sepium was identified by the FAO Panel of Experts on Forest Gene Resources in 1985 as meriting highest priority for exploration and evaluation (FAO, 1988). Several regional organizations are now involved with and promoting Gliricidia. These include the Centro Agronómico Tropical de Investigación y Enseñanza, CATIE, in Costa Rica (CATIE, 1986), the International Livestock Centre for Africa, ILCA (Sumberg, 1985), the Nitrogen Fixing Tree Association, NFTA (Glover and Brewbaker, 1984), and the Australian Centre for International Agricultural Research, ACIAR. In addition, several national research programmes are working with Gliricidia including those in the Philippines, Sri Lanka, Brazil and Colombia.
Systematic genecological investigations are lacking for Gliricidia with no complete studies to define its natural distribution, phenology and ecological amplitude, and variation. Most early introductions were poorly documented, and seed is likely to often have come from single provenances and often even a single parent tree (e.g. in Sri Lanka, where Gliricidia was introduced in 1880 probably from Trinidad (Weerawardene, pers. comm.) to, where it had been earlier imported from Nicaragua). Many land races 1 are, therefore, probably sub optimal and inbred. Atta-Krah (1986) has shown that all recent accessions tested in Nigeria have outperformed the local Ibadan land race. More recent seed collections have concentrated on small parts of the natural distribution. Sumberg (1985) collected a mixture of 54 family and bulk seedlots from North-Western Costa Rica while Chang and Martínez (1985) collected a series of provenances mainly from South-Eastern Guatemala and North-Western Costa Rica. Thus, present research on introduced Gliricidia is based on incomplete biological knowledge and narrowly based germplasm often from a very restricted part of the distribution.
Further Information
Readers who wish to have further information should contact the author of this article.
Acknowledgements
The assembly of seed collections has been carried out in close collaboration with the forest authorities of Mexico, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, Panama, Colombia and Venezuela. The work was financed by the UK Overseas Development Administration.
MAP1 TENTATIVE DISTRIBUTION of GLIRICIDIA SEPIUM & LOCATION of SEED COLLECTION SITES
References
Agboola, A.A., Wilson, G.F., Getahun, A. & Yamoah, C.F. 1981 Gliricidia sepium: a possible means to sustained cropping. In: MacDonald, L.H. (ed.). Agroforestry in the African Humid Tropics Proceedings Workshop, Ibadan, Nigeria. (U.N. University, Tokyo, Japan). (159 pp.).
Atta-Krah, A.N. 1986 Gliricidia Progress Report. (ILCA, Ibadan, Nigeria). (Unpublished). (24 pp.).
CATIE 1986 Silvicultura de especies promisorias para producción de leña en América Central. Serie Técnica. Informe Técnico No. 86. (CATIE, Turrialba, Costa Rica). (220 pp.).
Chang, B. & Martínez, H. 1985 Collection of Gliricidia sepium seed in Central America for provenance trials. Forest Genetic Resources Information 14: 50–55. (FAO, Rome).
Falvey, J.L. 1982 Gliricidia maculata - a review International Tree Crops Journal 2: 1–14.
FAO 1988 Sixth Session of the FAO Panel of Experts on Forest Gene Resources. (FAO, Rome).
Glover, N. & Brewbaker, J.L. 1984 Network trials of Gliricidia sepium. Nitrogen-Fixing Tree Research Reports 2: 34.
Hughes, C.E. 1986 Progress in collection and evaluation of NFT germplasm from Central America. Nitrogen-Fixing Tree Research Reports 4: 49–51.
Hughes, C.E. Biological considerations in designing a seed collection strategy for Gliricidia sepium (Jacq.) Walp. (Leguminosae). Commonwealth Forestry Review. (In press).
Hugues, C.E. & Styles, B.T. 1984 Exploration and seed collection of multiple-purpose dry zone trees in Central America. International Tree Crops Journal 3: 1–31.
National Academy of Sciences. 1980 Firewood Crops: shrub and tree species for energy production. (NAS, Washington, USA). (237 pp.).
Sumberg, J.E. 1985 Collection and initial evaluation of Gliricidia sepium from Costa Rica. Agroforestry Systems 3: 357–361.
