Effect of genotype of cocoa (Theobroma cacao) on attractiveness to the mirid Sahlbergella singularis (Hemiptera: Miridae) in the laboratory

BACKGROUND: Mirids are a major constraint to cocoa growing in Africa. Cocoa breeding for tolerance/resistance could be effective in an integrated pest management system. Attractiveness is one aspect of tolerance/resistance, and decreasing the attractiveness of cocoa trees should be a good way of reducing damage. RESULTS: Small-scale laboratory tests were carried out in Cameroon to assess differences in the attractiveness to mirids of eleven cocoa genotypes. The genotypes were ranked according to their attractiveness score and a distance from a mean value. An analysis of variance was performed and revealed significant differences between cocoa genotypes (F=3.15, P<0.001). The cocoa genotype groupings revealed three major categories, with BE10 and SNK413 proving to be the most attractive. In contrast, five genotypes, IMC60, the Catongo Trinitario genotypes, Playa Alta2 (from Venezuela), SIC5 and SNK614, proved to be less attractive than the mean. Four genotypes (PA107, SNK619, UPA134 and T60/887) displayed similar attractiveness to the mean. CONCLUSION: The circular microtest offered the advantage of not needing a reference cocoa genotype. The least attractive clones, such as IMC60, were also the most tolerant in the field. Comparisons with the results of other studies are proposed.