The native rice leaf folder can enhance rice resistance against the invasive fall armyworm by inducing the jasmonate‐mediated tryptophan metabolism pathway

BACKGROUND The fall armyworm (FAW), as a destructive invasive pest, poses a serious threat not only to maize production, but also to rice yield in Asia. Understanding plant‐mediated impacts of native insects on invasive counterparts is important to assess the consequences of biological invasions. Yet it remains unclear whether infestation by native pests such as the rice leaf folder (RLF) can enhance rice resistance, thereby limiting the FAW's capacity to invade paddies and preventing it from becoming a serious rice pest. RESULTS Here, we found that pre‐infestation by either the native RLF or FAW itself induces defenses and significantly reduces the performance of subsequently feeding FAW larvae. Transcriptomic analysis revealed that both herbivores activate the jasmonic acid (JA) signaling pathway. Consistently, exogenous methyl jasmonate (MeJA) application enhanced rice resistance to FAW, whereas inhibition of JA biosynthesis attenuated RLF‐induced resistance. Metabolomic profiling showed that herbivory induced the tryptophan metabolic pathway, leading to the accumulation of defensive tryptophan‐derived metabolites. Feeding assays confirmed that these metabolites, particularly tryptamine and 5‐methoxyindoleacetate, significantly suppressed FAW larval growth in a concentration‐dependent manner. The key role of JA‐tryptophan defense was further validated by exogenous application of MeJA, which upregulated the tryptophan pathway and increased defense metabolite accumulation. CONCLUSION Our findings reveal a potential mechanism whereby native herbivore attack induces the jasmonate and tryptophan metabolic pathways, thereby enhancing rice resistance to the invasive FAW. This provides mechanistic evidence for plant‐mediated biotic resistance and identifies the JA pathway and tryptophan‐derived metabolites as targets for sustainable pest management.