Population structure in Gliricidia sepium (Leguminosae) as revealed by isozyme variation
Gliricidia sepium (JACQ.) WALP. is a woody legume native to seasonally dry sites in Meso-America. It has been introduced to many other parts of the tropics, where it is utilised as a source of fuelwood, living fences, animal fodder and green manure by rural communities. These introductions have, however, been founded on a narrow, or unknown, genetic base, and poor growth performance has been reported at a number of locations. There is, therefore, a need to diversify the genetic base of this species in domestication, and to explore its population structure as a basis for this diversification. Here the authors report the use of isozyme markers to investigate the distribution of genetic diversity within and among populations of G. sepium. Marked differentiation between populations (FST= 0.172) was observed, although most variation occurred within populations. Averaged over all populations, there was a mean number of alleles per locus (A) of 2.0, a mean percentage polymorphic loci (P) of 60% and a mean observed heterozygosity (Ho) of 0.238, values which suggest a rather higher level of genetic diversity than those reported from other comparable species. The values of these variables, however, differed considerably between populations, those believed to be native maintaining higher levels of variation than those believed to be naturalised or introduced. Some of the most genetically diverse populations have also been recommended for forage and fuelwood production, indicating that there is a sound basis for the genetic improvement of this species.
Silvae Genetica (1996) 45 (2/3) 112-118