Morphological characterization of traditional cacao (Theobroma cacao L.) plants in Cuba

Plantations of cacao (Theobroma cacao L.) more than 60 years old still exist in Cuba and are probably quite similar to the original introductions. We studied the phenotypic diversity of a representative sample of 537 traditional Cuban cacao plants and 165 reference plants from the different T. cacao genetic groups, using 33 morphological descriptors. The results were compared with the previously determined allelic compositions at 15 simple sequence repeat (SSR) loci designated as international standards. Most morphological traits showed high variation, with all but one found to be polymorphic. The most frequent character states were (1) in the seeds: flat transversal sections, intensely violet color and slightly acidic flavor, (2) in the fruit: yellow color at maturity with no anthocyanin, ten ridges distributed in five pairs, medium-depth furrows, intermediate rugosity and hard mesocarp and (3) in the flower: divergent, intensely purple staminodes, white horizontal sepals, intense yellow petals, white stamen filaments, light purple peduncles and white closed flowers. By comparison with reference plants, the traditional Cuban cacao samples were classified as Trinitario group members using cluster and multiple correspondence analyses. We found associations among several fruit color states and allelic forms at mTcCIR12, a locus probably related to anthocyanin pigmentation. Other fruit morphological trait states were related to one another and were correlated with 10 SSR markers, reflecting the complex genetic basis of T. cacao fruit morphology. Cotyledon color was associated with the mTcCIR18 locus in linkage group 4, and thus most likely near loci coding for this trait.