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Field tests for antixenosis and tolerance of cocoa towards mirids

Babin R., Sounigo O., Dibog L., Nyassé S.. 2004. Ingenic newsletter (9) : p. 45-50.

Field tests for antixenosis (feeding non-preference) and tolerance of cocoa trees to mirid damage were conducted as part of the CFC/ICCO/IPGRI Project, in the budwood garden of IRAD Nkolbisson Station. Antixenosis was assessed by counting the number of mirid bites on the flush after 24 hours, while assessment of tolerance was based on regular observations of the evolution of mirid damage and of the ability of twigs to recover from it. An analysis of covariance, with the surface area of the flush leaves as a covariable, revealed a highly significant effect of the clone on the number of mirid bites, and SIC 5 and CATONGO showed a stronger effect of antixenosis than the other clones. The results obtained by observing the evolution of mirid damage and the sprouting of twigs revealed that the ability of clones to contain the extent of damage, and their ability to recover from it must be considered as two distinct components of genetic resistance to mirid attack. The analysis of covariance also revealed a highly significant effect of clones for these two components. UF 676 and IMC 60 showed the best ability to contain the degree of damage, while PLAYA ALTA 2, ICS 1 and UF 676 were the best clones in terms of ability to recover from mirid damage.

Mots-clés : theobroma cacao; miridae; résistance aux organismes nuisibles; dégât; essai de variété; clone; cameroun

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