**10. Conclusion**

The aphid-plant coevolution is a continuous arms race that helps to improve defense strategies employed by plants to ward off aphids and counter defense mechanisms employed by aphid herbivores. For a compatible aphid-plant interaction, aphids not only need to alter local and systemic events but also need to modify resource allocation to suit phloem sap to their requirements. Generally, the JA-mediated defenses are employed by plants to control aphids. But aphids through the use of specific effectors are able to modify the JA-mediated defense response of plant and are able to establish successful feeding. Plants, on the other hand, have evolved to use aphid salivary components as elicitors of defense response. The phloem sealing mechanism is one such response observed in resistant plants. In addition, plants have also evolved a plethora of plant secondary metabolites (PSMs) that have defensive functions. But some specialist aphids have learned to use these compounds to their own advantage and use them as cues for feeding and colonization and even sequester them for their advantage.

The current knowledge on aphid-plant interactions is still in its infancy. But the recent studies have provided insights into such interactions which will have far-reaching implications at different levels including development of novel aphid management strategies.
