EVALUATION OF THE EXTENT OF GENETIC-VARIABILITY AMONG THEOBROMA-CACAOACCESSIONS USING RAPD AND RFLP MARKERS

Random amplified polymorphic DNA (RAPD) and restriction fragment lengt h polymorphism (RFLP) markers were used to evaluate genetic relationsh ips within the Theobroma cacao species and to assess the organization of its genetic diversity. Genetic variability was estimated with 18 pr imers and 43 RFLP probes on 155 cocoa trees belonging to different mor phological groups and coming from various geographic origins. The majo rity of the RFLP probes issued from low-copy DNA sequences. On the bas is of on the genetic distance matrices, the two molecular methods gave related estimates of the genetic relationship between genotypes. Alth ough an influence of cocoa morphological groups and geographical origi ns of trees was observed, a lack of gene differentiation characterized the T. cacao accessions studied. The continuous RFLP variability obse rved within the species may reflect the hybridization and introgressio ns between trees of different origins. Nevertheless, the Nacional type was detected to be genetically specific and different from well-known types such as Forastero, Criollo and Trinitario. Some of those genoty pes were characterized by a low heterozygosity rate and may constitute the original Nacional pool. These results also provide information fo r the constitution of a cocoa tree core collection.