Beyond Bt: Alternative Strategies for Insect-Resistant Genetically Modified Crops

Abstract

Bacillus thuringiensis (Bt) plants dominate today’s commercial market for insect-resistant transgenic crops. However, not all pests are susceptible to Bt Cry toxins and there are concerns that even susceptible species may evolve to become resistant to these crops. The search for alternatives is well under way, with significant progress already made towards producing transgenic crops expressing insecticidal compounds from plants, such as protease inhibitors, lectins and alpha-amylase inhibitors. New types of proteins from B. thuringiensis, such as the vegetative insecticidal proteins, are also being exploited. At an earlier stage of development but attracting much research interest are other insecticidal compounds, such as chitinases, defensins, enhancins, biotin-binding proteins, proteases and toxins, sourced from bacteria, viruses, plants and arthropods. Fusion proteins, combining the features of different insecticidal proteins, have significant potential for extending the range of insect species which could be controlled via transgenic plants. In the future, metabolic engineering of plants could allow us to alter with great precision the ways in which plants and insects interact. The compatibility of these novel insect control strategies with biological control and integrated pest management is discussed.