Genetic variation in Leucaena leucocephala (Lam.) de Wit. (Leguminosae: Mimosoideae).

Abstract

Leucaena leucocephala is a multipurpose neotropical tree with a long history of human use, which is now distributed pantropically. The level of genetic variability within and among 24 populations of L. leucocephala (from Mexico, Guatemala, Honduras, Haiti and Madagascar) was assessed using isoenzyme analysis (324 plants; 12 populations) and restriction analyses (23 populations) of the chloroplast DNA (ctDNA) and nuclear ribosomal DNA (rDNA). In a survey of three isoenzyme systems (aspartate aminotransferase, peroxidase and phosphoglucose [glucose-6-phosphate] isomerase), multi-enzyme phenotypes were encountered such that it was possible to identify the two sub-species of L. leucocephala and inter-population differentiation. Partitioning of phenotypic diversity within and among populations revealed that 76% of the variation resided among populations. Evidence of either multiple introductions or hybridization/introgression was found in a Haitian collection. Seven restriction fragments showed ctDNA variation and there was evidence for between 1 and 5 rDNA repeats per population. These results are discussed in relation to the utilization of L. leucocephala as a multipurpose tree crop.