Ecological constraints to the deployment of arthropod resistant crop plants: A cautionary tale
About 300 insect-resistant crop varieties are grown in different parts of the world and the majority of these are used in major cereal production systems. Until now development of these cultivars has been the product of selection programs that use germplasm derived From geographical regions where the insect is endemic or the plant originated. Recent advances in plant molecular biology have the potential to change this approach as the technology offers the opportunity to insert novel sources of insect resistance in the host plant through the introduction of foreign primary gene products. This technology will influence both the rate at which new cultivars con be developed and, eventually the range of novel resistance characteristics that can be incorporated into plants. These changes could have a profound impact on pest management practices. However, the impact of synchronous use of resistant cultivars, based on single genes, across regions will require careful management if this approach is to be sustainable. In addition, transgenic plants are only one component of integrated management practices and their influence on preferred agronomic characters and beneficial organisms needs careful evaluation.In this paper we examine a range of ecological issues that need to be addressed if the potential of resistant host plants is to be fully exploited. These includea. how to develop deployment strategies that maintain susceptibility in the pest populationb. the potential consequences of ontogenetic, seasonal and environmentally-mediated expression of resistance traitsc. the impact of the introduced foreign genes on plant fitness and the way 'costs of resistance' and pest dynamics interact, andd. determining the potential consequences For multi-trophic interactions.These questions are explored through examination of the literature on insect-plant interactions and models of the dynamics of insect populations.