Overexpression of salicylic acid methyltransferase ( ZmSAMT ) enhances resistance to Rhopalosiphum padi in maize

BACKGROUND Aphids are important pests of maize, including Bt‐transgenic maize, and their effective management remains a major challenge. Herbivore‐induced plant volatiles (HIPVs), particularly methyl salicylate (MeSA), play a critical role in mediating tritrophic interactions and plant defense in agroecosystems. Exogenous application of synthetic MeSA can be effective against aphids, however, its pronounced volatility and maintenance costs limit large‐scale agricultural applications. RESULTS In this study, we generated ZmSAMT ‐overexpressing transgenic maize to enable continuous endogenous MeSA emission, establishing a sustainable strategy for aphid management. In vitro enzymatic assays confirmed that ZmSAMT specifically methylated salicylic acid (SA) to form MeSA. Notably, aphid infestation triggered significant upregulation of ZmSAMT expression in wild‐type maize. Behavioral assays demonstrated that elevated MeSA emission in transgenic line OE3 significantly repelled Rhopalosiphum padi and actively recruited the predator ladybeetle Harmonia axyridis . Independent of olfactory‐mediated effects, aphids feeding on OE3 plants exhibited prolonged developmental duration, a shortened reproductive period, and reduced total fecundity. Furthermore, we observed a significant airborne defense effect that wild type maize situated adjacent to the transgenic plants OE3 harbored fewer aphids. CONCLUSION Taken together, our studies indicate that ZmSAMT represents a highly valuable genetic resource for breeding aphid‐resistant maize varieties and developing green pest control strategies.