Bioengineering plant volatile emissions: prospects for plant protection against insect herbivores

Genetically engineered crop plants for enhanced emission of herbivore-induced plant volatiles (HIPVs) offer great potential in reducing the herbivore load on crops by repelling insect herbivores directly or attracting their natural enemies. Plant volatile organic compounds (VOCs) are also essential for pollination, insect reproduction, allelopathy, and serve as antimicrobial agents. Existing research in this field revolves around the routine chemical ecological experiments like identifying VOCs, HIPVs, and synthetic blends. Therefore, a deeper understanding of the role of enhanced volatile emissions and volatile biosynthetic pathways involved in chemical communication can lead to the development of behavior-based novel pest management strategies and lay the foundation for future research in these approaches. Recent discoveries in identifying and isolating the enzymes and genes associated with the biosynthetic pathways of volatiles have opened new avenues for the genetic engineering of crops. Genetically engineered plants could be developed to release volatiles only with an herbivore attack to conserve plant resources by mimicking a natural defensive strategy for direct repellence and/or recruitment of natural enemies. Crops engineered for sustainable volatile production can also serve as companion plants in the push and pull strategies and modify insect behavior to reduce the pest damage. A crop bioengineered for enhanced repellence of oviposition and increased release of insect pheromone-resembling compounds could benefit pest management programs. Further advanced research under field conditions is required to assess the physiological and ecological consequences, especially to the crop and the environment.