Egg-induced defensive volatiles in rice: a strategy to recruit egg parasitoids for biological control of rice stem borers

Plants deploy a sophisticated arsenal of chemical defenses to combat herbivore threats, utilizing semiochemicals that recruit natural enemies for protection. Oviposition-inducing plant volatiles (OIPVs) play a pivotal role in mediating plant-natural enemy interactions. This study delves into the behavioral responses of Trichogramma japonicum to volatile compounds emitted by rice plants following oviposition by the rice striped stem borer (SSB), Chilo suppressalis. Employing a Y-tube olfactometer, we evaluated the attraction of Trichogramma wasps to SSB-infested rice plants. Our findings indicate a pronounced preference of the wasps for rice plants directly subjected to SSB oviposition. Through gas chromatography-mass spectrometry (GC-MS) analysis, we identified six volatile compounds, D-limonene, linalool, nonanal, methyl salicylate, longifolene, and heptadecane, that were significantly more abundant post-SSB egg deposition. Subsequent Y-tube assays confirmed that these compounds attract female wasps in a dose-dependent manner. This research underscores the critical role of SSB egg deposition in modifying rice volatile profiles, thereby increasing the plant's attractiveness to Trichogramma wasps via specific more abundant volatiles. Our results illuminate the intricate tri-trophic interactions among rice, herbivores, and parasitoids, offering novel insights into plant-insect dynamics and paving the way for enhanced biological control strategies. This study not only reveals how T. japonicum responds to volatiles induced by SSB egg deposition but also contributes to our understanding of the chemical ecology underlying plant defense mechanisms.