Resistance of cacao (Theobroma cacao L.) to Sahlbergella singularis (Hemiptera: Miridae): investigation of antixenosis, antibiosis and tolerance

Cacao genotypes of various origins were evaluated for resistance to the cocoa mirid (Sahlbergella singularis (Haglund)) based on field damage, antixenosis, antibiosis and tolerance. Field damage was assessed by scoring recent and cumulative damage by the mirid to the major genetic groups of cacao. Antixenosis assessment was based on the number of feeding lesions on twig segments using a choice test. Antibiosis was measured through survival of young mirid nymphs on shoots and pods, whereas tolerance was assessed through the reaction of the twigs to mirid feeding punctures. Among the genetic groups of cocoa, the Upper Amazon, the materials from Guiana and hybrid genotypes were the least damaged by the mirids, both for recent and cumulative damage. The Catongo group was, by far, the most susceptible group with more than 50% of the canopy showing both recent dieback and cumulative canker damage. With regard to antixenosis, antibiosis and tolerance, significant differences (P