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Genetic differentiation of cocoa (Theobrotna cacao L.) populations revealed by RAPD analysis


  • One of our research themes is the development and exploitation of molecular polymorphic assay procedures for tropical tree species. Joanne Russell (née Wilde) is a postgraduate student registered in the Department of Agricultural Botany, University of Reading. Liz Johnson and Felicia Hosein are visiting workers from the Cocoa Research Unit (CRU), University of West Indies, who are concerned with the transfer of PCR-based technology developed by Joanne Russell to CRU. The research is directed and co-ordinated by Wayne Powell and Robbie Waugh.

Wayne Powell


In order to preserve and exploit the valuable genetic resources of tropical forest trees, such as cocoa, a systematic assessment of the available genetic variability is necessary. The approach we have used is based on a simple mini-prep DNA extraction procedure together with a polymerase-chain-reaction- (PCR)-based polymorphic assay procedure (RAPD). Twenty-five cocoa accessions: IMCs and PAs collected from Peru and LCTEENs collected from Ecuador, which are difficult to distinguish using morphological or biochemical descriptors, were uniquely fingerprinted using a minimum of three oligonucleotide primers. Analysis of the variability detected using RAPDs clearly discriminated between the geographical origin of the three cocoa populations. Partitioning of variability into within and between population components revealed that most variation was detected within a population. The potential of RAPD analysis to facilitate the rationalization of field gene banks and provide accurate estimates of diversity to allow optimization of collecting strategies is discussed

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