Decoding the chemical conversation: amino‐oligosaccharides induce rice volatiles to modify host selection of the egg parasitoid Trichogramma japonicum

BACKGROUND: Plants deploy sophisticated defense strategies, including emission of volatile organic compounds that attract natural enemies of herbivores. Although plant immunity inducers such as amino-oligosaccharides (AOS) are known to enhance direct resistance against pathogens, their influence on tritrophic interactions through the modulation of plant volatiles remains unclear. This study investigates how AOS treatment affects rice volatile-mediated attraction of the egg parasitoid Trichogramma japonicum and its parasitism behavior toward the rice striped stem borer (SSB, Chilo suppressalis). RESULTS: AOS treatment significantly reduced the attractiveness of rice plants to T. japonicum, decreasing parasitism by 33.2% compared with the control. Gas chromatography-mass spectrometry profiling identified 11 differentially emitted volatiles, among which six compounds-methyl salicylate, decanal, d-limonene, 6-methyl-5-hepten-2-one, octanal, and eucalyptol-exhibited concentration-dependent effects on parasitoid orientation. Metabolomic analysis indicated that AOS activates salicylic acid biosynthesis and enhances trypsin protease inhibitor activity, while concurrently altering the composition of the volatile blend. CONCLUSION: AOS primes rice defense responses but reduces parasitoid recruitment, unveiling a trade-off between direct and indirect plant defenses. The identification of key behaviorally active volatiles and their dose-dependent effects provide novel insights into plant-insect chemical ecology. These findings deepen our understanding of the ecological consequences of plant immunity inducers and lay the foundation for precision plant protection strategies that balanced resistance with conservation biological control. © 2026 Society of Chemical Industry.