Assessment of the yield of individual cacao trees in four field trials.

Abstract

In four field trials of Upper Amazon cacao hybrids 16.8- 27.2 % of the cacao trees produced no useable pods, 38.8-66.3 % yielded 1-10 pods and 6.8-38.0 % had more than 10 pods per year. Some trees of T60/887 progenies were very high yielding and produced up to 180 pods per year. Tree-to-tree variation in yield was very high (C.V. = 30.2- 76.0%). Heritabilities for individual tree yield were very low, hence it is recognised that this variation is partly due to environmental and partly due to genetic factors. In our study, individual tree yield was highly correlated with stem girth, suggesting that inter-tree competition may be involved. There were no significant differences between the yields of the control crosses at the four trial sites, indicating that there was very little genotype x environment interaction. The results indicate that breeders should aim at a high proportion of individual trees contributing to yield in any selected variety. This could be improved, on one side, by using more uniform cacao varieties (i.e. clones or genetically uniform hybrid varieties). On the other side, environmental effects could be reduced by applying good and uniform agronomic practices, which might include the thinning of densely planted cacao stands at adult age to reduce inter-tree competition.