Progeny trials were planted at Tafo in 1952 and 1954 to compare 3 selfed local-Trinitarios, 1 outcrossed and 3 sibbed Upper Amazon progenies and 13 hybrids between Amelonado or local-Trinitarios and Upper Amazons; 1 trial included West African Amelonado. The Amazon hybrids and the outcrossed Amazon were particularly vigorous and precocious and maintained a yield advantage for 20 years. The 13 hybrids were similar in yield potential, but varied in net yield following differential losses from pod diseases, mainly caused by
Phytophthora palmivora. Disease losses were lowest on one of the sibbed Amazons and the outcrossed Amazon and lower on Amelonado than on any of the 7 hybrids tested with it; in both trials losses were lower on Amelonado hybrids than on Trinitario hybrids.
There was wide variation in both size and growth rates of mature trees and no consistent relationship between continued growth and crop. It seemed that later yields were not prejudiced by the precocity of Amazon hybrids, the yields from all types fluctuated together. Because the differences in disease losses are likely to be accentuated under farmer's conditions. Amelonado hybrids are preferable to local-Trinitario hybrids. The results also suggest that commercially acceptable pure Upper Amazon varieties could be developed.
Index words
Theobroma cacao
- cacao - cocoa - Amelonado - Upper-Amazon hybrids - yield - growth - blackpod - Ghana
On secondment on technical assistance from the United Kingdom Ministry of Overseas Development.