Gene pyramiding: A strategy for insect resistance management in <em>Bt</em> transgenic crops

Abstract

Preventing or delaying evolution of resistance in insects through adoption of judicial resistance management strategy is critical for the sustainable use of <em>Bt</em> transgenic crops. Strategies for resistance management in insect resistant <em>Bt</em> crops include: high dose strategy, moderate dose strategy, temporal- or time-specific toxins expression, refuge strategy, gene pyramiding/stacking, mixtures, rotations or mosaics of transgenic plants. Among these, pyramided/stacked plants have the potential to delay resistance more effectively than sequential deployment of single <em>Bt</em> toxin containing plants or in mosaics, even with relatively small and more economically acceptable refuge size. Resistance can be delayed for extended period even by reducing the refuge size if two or more toxin coding genes are pyramided in a single plant. If toxins are used independently, there is a possible risk of cross-resistance among the toxins.