Abstract: 【Aim】 This study aims to explore the mechanism of aphid feeding-induced salicylic acid (SA) in improving the insect resistance of potato (Solanum tuberosum) under potassium application, so as to provide the scientific basis for insect resistance in crops. 【Methods】 The endogenous contents of SA and proline, and the activities of phenylalanine ammonia lyase (PAL) and antioxidases including peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in potato leaves after potassium application (6 g potassium sulphate/plant), insect damage (aphid feeding, 5 adults of Myzus persicae/plant), potassium application plus aphid feeding, and spraying exogenous SA (20 mL/plant at the concentrations of 15, 30 and 45 μmol/L, respectively) were measured. 【Results】 The results showed that the SA contents in potato leaves in the treatment groups of potassium application, aphid feeding, and potassium application plus aphid feeding were 1.1, 1.3, and 1.5fold higher than that in the untreated control, respectively, and the PAL activities in these treatment groups were increased by 23.3%, 223% and 35.0% as compared to that in the untreated control, respectively. Both the SA content and PAL activity in potato leaves with potassium application plus aphid feeding were the highest among the above three treatments. Irrespective of potassium application, the SOD activities in potato leaves were increased significantly when the potato plants were sprayed with 15 μmol/L SA. After potassium application, the POD activities in potato leaves treated with SA at the doses of 15 and 45 μmol/L were 1.7- and 1.8-fold as high as those of the corresponding controls, respectively. Similarly, the CAT activities in potato leaves in potassium application group treated with SA at the doses of 15 and 30 μmol/L were 1.3- and 1.5-fold as high as those of the control groups, respectively. After 15 μmol/L exogenous SA was sprayed on potato leaves, the proline content in the treatment group (1.2 OD/g pro) was significantly higher than that in the control group (0.4 OD/g pro). 【Conclusion】 Both treatments of aphid feeding and potassium application plus aphid feeding significantly enhance the endogenous SA content and the PAL activity in potato leaves. Spraying exogenous SA at the dose of 15 μmol/L on potato leaves can significantly increase the activities of anoxidases including POD, SOD and CAT and the proline content in the potassium application group, indicating that 15 μmol/L SA is the most suitable treatment concentration. At this treatment concentration a positive interaction between applying potassium and SA happens. The results suggest that both aphid feeding and potassium application can increase the SA signal pathways and so enhance plant resistance to pest insects.

Key words: Solanum tuberosum, salicylic acid, potassium fertilizer, Myzus persicae, anoxidase, proline content