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Evaluation of resistance of Theobroma cacao mirids in Côte d'Ivoire : Results of comparative progeny trials

Sounigo O., Coulibaly N., Brun L., N'Goran J.A.K., Cilas C., Eskes A.. 2003. Crop Protection, 22 (4) : p. 615-621.

DOI: 10.1016/S0261-2194(02)00244-2

Susceptibility of Theobroma cacao L. to mirids (Distantiella theobromae Distant and Sahlbergella singularis Haglund) was assessed in four seedling progeny trials planted in Côte d'Ivoire by visual estimation of the cumulative damage on a 5 point scale. Although a significant effect of the progenies was identified in all trials, a clear discrimination between entries was only observed in one trial. In three trials, set up according to a North Carolina II design, it was possible to rank the female or the male parents according to the values of their progenies. Genotypes from the upper amazon Forastero appeared to include the most promising parents, while germplasm from the Trinitario (Central America) group appeared as the least promising. A good correlation (R = 0.85) between the phenotypic level of susceptibility of six clones and their general combining ability was observed in one of the trials but not in another trial. Broad and narrow sense heritabilities were identical, varying between 0.09 and 0.38, according to the trial. The highest value was found for the trial comparing genetically diverse parents, represented by a high number of offspring. The prospects of including mirid resistance in cocoa breeding programs are discussed.

Mots-clés : theobroma cacao; résistance aux organismes nuisibles; sahlbergella; miridae; essai de variété; critère de sélection; aptitude à la combinaison; héritabilité; clone; distantiella theobromae

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