VARIABILITY FOR NUCLEAR RIBOSOMAL GENES WITHIN THEOBROMA-CACAO

Restriction fragment length of the rRNA genes was studied in Theobroma cacao using heterologous rDNA probes. One hundred and ninety-two indi viduals including both cultivated and wild clones were analysed. DraI and EcoRI restriction sites were mapped. Both length heterogeneity and restriction site polymorphism have been found. Fifteen different type s of rDNA units have been characterized. As opposed to previous enzyma tic studies, the rRNA gene analysis indicates a clear distinction of t he three genetic groups Criollo, Forastero and Trinitario within cocoa and points out the hybrid origin of Trinitario.