EVIDENCE OF GENETIC DIVERSITY AND TAXONOMIC DIFFERENTIATION AMONG ACACIA SENEGAL POPULATIONS AND VARIETIES IN KENYA BASED ON RANDOMLY AMPLIFIED POLYMORPHIC DNA MOLECULAR MARKERS

Abstract

Acacia senegal is a multipurpose tree species that forms an essential component of many farming systems in Sub-Saharan Africa where it is commercially exploited for gum arabic production. However, the species is yet to be put to optimal production in some countries due to inadequate information on its population genetics and taxonomic delimitation. This study reports the use of 13 randomly amplified polymorphic DNA (RAPD) markers to determine genetic diversity and taxonomic relationships among 12 natural populations of A. senegal in Kenya. High genetic diversity was found for all populations. Mean gene diversity (He) for all populations was at 0.288 with effective number of alleles per locus (Ne) of 1.496. Analysis of molecular variance (AMOVA) revealed most genetic variations residing within (60%) rather than among populations. However, significant differentiation was detected among populations (ɸst = 0.130; P < 0.001). Cluster analysis based on similarity coefficient delimited three main groups corresponding to the three putative varieties of A. senegal namely senegal, kerensis and leiorhachis. The RAPD technology suggested high genetic diversity within the species and taxonomically differentiated the three varieties, however, there was evidence of admixture among the varieties. For high quality gum production and better economic returns, gum arabic collections should be designed based on the varieties and their locations. Seed collections for tree improvement or conservation programmes should take into account the groups detected for quality controls.