ALLOZYME DIVERSITY IN A GERMPLASM COLLECTION OF THEOBROMA-CACAO L

Allozyme data for eight polymorphic loci encoding six enzymes were used to describe 86 clones from the USDA/ACRI Theobroma cacao germplasm collection. To further characterize gene diversity, the total population was subdivided two ways: by geographical origin and by morphological type. Contingency chi(2) analysis showed the Caribbean and Central American groups to be distinct from South American clones. Among types, the Forasteros differed from the Trinitarios at four of six loci. Some differences were due to the presence or absence of certain alleles. Phenetic trees were constructed using gene frequency data averaged over groups. Most gene diversity was found to exist within, rather than between, groups; this differentiation was somewhat higher among morphological types than among geographical origins. A core collection of clones selected across all morphological types, using both morphological and allozyme descriptors, might provide an optimal method of maintaining a germplasm collection of this species.