Abstract: Aphid infestation is one of the most important factors that affects the yield and quality of potato (Solanum tuberosum), whereas polyphenol oxidase (PPO) is a significant anti-insect trait in plants. In order to clarify the interaction between potato and peach aphid (Myzus persicae) after potassium supply, the changes of PPO activity in patato leaves in four treatments, i. e., the control (no potassium supply, no aphid feeding), aphid feeding, potassium supply and aphid feeding plus potassium supply, were assayed using colorimetry, iTRAQ technique and Western blotting. The results indicated that the population size of peach aphid decreased significantly after potassium supply compared with that of the control group in the development processes. Potassium supply of 6 g/seedling had the highest inhibitory effect on the growth of peach aphid populations. The PPO activity in potato leaves increased by 44% and 67% after potassium supply of 6 g/seedling and aphid feeding plus potassium supply, respectively. LC-MS/MS analysis showed that the expression level of PPO protein was up-regulated in varying degrees after the potato leaves were subjected to aphid feeding, potassium supply and aphid feeding plus potassium supply. Western blotting results showed that the relative expression level of PPO increased significantly in treatments of potassium supply and aphid feeding plus potassium supply, and presented the highest relative expression level in aphid feeding plus potassium supply treatments. The results suggest that potassium supply and aphid feeding plus potassium supply may enhance potato resistance to aphids due to, at least in part, the induction of PPO activity in its leaves.

Key words: Solanum tuberosum, potassium supply, aphid infestation, Myzus persicae, polyphenol oxidase (PPO), insect resistance