Studies on the Effects of Cross-Incompatibility on the Cropping of cocoa in Ghana

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Abstract
Summary The effects of self- and cross-incompatibility on yield in cocoa were studied in six Amazon X Trinitario or Amelonado progenies in two 20-year-old progeny trial areas at Tafo, Ghana. The patterns of segregation for compatibility alleles corresponded to the accepted theory of incompatibility in cocoa. Differences in yield between compatibility groups within progenies were measured by regression of yield on tree size, on a tree-by-tree basis. In progenies where half the trees were self- compatible, there were indications that the self-compatible trees were higher yielding than the incompatible trees, whereas when all the trees were self-incompatible the half with highly restricted cross compatibility were lower yielding than the half which were more freely cross-compatible. Self-compatible trees cropped earlier in the season than incompatible trees of the same progeny. In entirely self-incompatible progenies there were no differences in cropping patterns between parents differing in S alleles. There was no evidence of variation in pod characters between compatibility groups within a progeny or within plots. The need to plant mixtures of progenies with differing S alleles is stressed. It is suggested that breeders should avoid using clones with independent compatibility alleles as female parents in seed gardens.

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