An assessment of genetic diversity among marula populations using the amplified fragment length polymorphism (AFLP) technique

Marula is a wild-growing dioecious leafy tree species indigenous to Africa. The species exhibits a high phenotypic variability, especially in fruit size and quality and these traits are exploited by indigenous communities for commercial gain. As a first step towards assessing the relationship between the phenotypic and genotypic properties of the marula species, the genetic structure of natural marula populations was assessed using the Amplified Fragment Length Polymorphism (AFLP (TM)) technique. Seven primer combinations were used to assess the degree of genetic diversity within and among natural marula sampled from the Bochum, Tzaneen and Nelspruit areas of South Africa. A total 141 unambiguous bands were amplified, of which 83 (59%) displayed polymorphism in one or more populations. Representative levels of genetic diversity were observed within all local populations. Coefficients of genetic differentiation showed evidence of drift among populations from the Limpopo- and Mpumalanga Provinces. A Bayesian assignment technique supported this trend, and suggested a true genetic structure of two populations, containing the Limpopo and Mpumalanga trees respectively. This diversity provides a plausible foundation for the marked phenotypic variation observed in marula, and suggest genetic diversity to provide for artificial selection during future artificial propagation programmes is present.