Abstract: 【Aim】 Utilizing chemical elicitors to enhance the resistance of plants to insects and suppress pests is a new green pest management strategy. In this study, we investigated the underlying mechanisms of a chemical elicitor paclobutrazol (PBZ) in inducing the resistance of rice (Oryza savita) to rice planthoppers, to lay a foundation for future application in pest management. 【Methods】 Xiushui 110 rice plants were respectively grown in nutrient solutions containing different concentrations of PBZ for 24 h, then the newly hatched larvae of the brown planthopper, Nilaparvata lugens, or the white-backed planthopper, Sogatella furcifera were introduced, and their nymphal survival rates were determined at different time post insect infestation. The survival rates of N. lugens nymphs fed with the artificial diets containing 5 mg/L PBZ, 10 mg/L PBZ and defensive compounds ［caffeoyl putrescine, carlinoside and prunin (1 and 10 mg/L), and mustard acyl agmatine (0.1 and 1 mg/L)］, or sprayed with 5 and 20 mg/L PBZ solutions, were also measured. Moreover, the contents of signal molecules including salicylic acid (SA), hydrogen peroxide (H₂O₂) and ethylene (ET), and the defensive compounds mustard acyl agmatine, caffeoyl putrescine, carlinoside and prunin in rice plants grown in nutrient solutions with 5 mg/L PBZ, infested by N. lugens nymphs, and grown in nutrient solution with 5 mg/L PBZ and then infested by N. lugens nymphs were detected. 【Results】 When N. lugens nymphs fed on rice plants that were grown in nutrient solution containing 5 mg/L PBZ, their survival rate was reduced by 33.3% at 3 d after feeding, as compared to that in the control ［grown in nutrient solution without PBZ］, and when feeding on rice plants grown in nutrient solution containing 20 mg/L PBZ, nearly all nymphs died at 4 d. However, PBZ itself showed no direct toxic effects on N. lugens nymphs. The SA content in rice plants grown in nutrient solution with 5 mg/L PBZ for 24 h but without BPH infestation for another 24 h, and the H₂O₂ content in rice plants grown in nutrient solution with 5 mg/L PBZ for 24 h and then infested by N. lugens nymphs for 72 h significantly increased, and the contents of ET emitted from the rice plants grown in nutrient solution with 5 mg/L PBZ for 24 h but without BPH infestation for another 48-96 h, infested by N. lugens nymphs for 24-72 h, and grown in nutrient solution with 5 mg/L PBZ for 24 h and then infested by N. lugens nymphs for 48-96 h significantly reduced as compared with those in the control group . In addition, treatment with 5 mg/L PBZ induced the significant enhancement in the contents of two phenolic amine compounds (caffeoyl putrescine and mustard acyl agmatine) and two flavonoid compounds (carlinoside and prunin). The survival rates of N. lugens nymphs were significantly reduced when they fed on the artificial diets containing 1 or 10 mg/L caffeoyl putrescine, mustard acyl agmatine, carlinoside or prunin. 【Conclusion】 PBZ is an effective chemical elicitor that can significantly enhance the resistance of rice plants to rice planthoppers by activating the SA and H₂O₂ pathways, and inhibiting the ET pathway, as well as inducing the synthesis of related defensive compounds in rice.

Key words: Rice; Nilaparvata lugens, paclobutrazol, chemical elicitors, induced resistance