GENETIC-VARIATION IN LEUCAENA-LEUCOCEPHALA (LAM) DE WIT (LEGUMINOSAE,MIMOSOIDEAE)

Leucaena leucocephala (LAM.) DE WIT. is a multi-purpose neotropical tr ee, with a long history of human use, which is now distributed pantrop ically. The level of genetic variability within and among 24 populatio ns of L. leucocephala has been assessed using isozyme analysis (324 pl ants; 12 populations) and restriction analyses (23 populations) of the chloroplast DNA (cpDNA) and nuclear ribosomal DNA (rDNA). In a survey of three isozyme systems (AAT; PER; PGI) multi-enzyme phenotypes were encountered such that it was possible to identify the two subspecies of L. leucocephala and inter-population differentiation. Partitioning of phenotypic diversity within and among populations revealed that 76% of the variation resided among L. leucocephala populations. Evidence of either multiple introductions or hybridisation/introgression was fo und in a Haitian collection. Seven restriction fragments showed cpDNA variation and Evidence for between 1 and 5 rDNA repeats per population was encountered. These results are discussed in relation to the utili zation of L. leucocephala as a multi-purpose tree crop.