Sources of pest resistance in cassava

Cassava (Manihot esculenta Crantz), a primary food crop in developing countries, can be severely affected by the attack of several Neotropical pests. To contribute to their management, this study sought to identify genetic resources for resistance breeding within the world's largest cassava genebank, held at the International Center for Tropical Agriculture (CIAT), in Colombia. We compiled data from 89 field trials between 1980 and 2004 evaluating natural mite, thrips, and whitefly herbivory in hundreds of cassava genotypes. Highly susceptible genotypes were excluded from subsequent evaluations within one or two trials. Statistical analyses estimating resistance were therefore performed only for genotypes evaluated for a given pest in at least three trials. These analyses revealed potentially-useful genotype variation in resistance to Mononychellus tanajoa (Bondar), Aleurotrachelus socialis Bondar, and Frankliniella williamsi Hood. Based on this variation, we identified 129 potential sources of resistance to F. williamsi, 33 to M. tanajoa, and 19 to A. socialis. Leaf pubescence was positively associated with resistance to the three pests, and root cyanide was negatively associated with resistance to A. socialis. Our results support the potential for developing improved cassava cultivars with high pest resistance.