Abstract: More and more attention was paid to the induced resistance in plant pest control. In order to explore a new control method for wolfberry pests, the induced defense response in wolfberry and the defense mechanism were studied. The changes of activities of protease inhibitors (PIs), superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL), and the contents of polysaccharide and xylogen in wolfberry (Lycium barbarum) leaves subjected to exogenous JA treatment and damage by gall mite Aceria pallida were tested. The results showed that the activities of PIs, SOD and PAL and the xylogen content increased significantly in wolfberry leaves subjected to treatments with JA at the concentrations of 0.001 and 0.1 mmol/L and the damage by A. pallida compared with the control not subjected to JA treatment and the damage by A. pallida， but the polysaccharide content was dramatically reduced. The JA treatment or the damage by A. pallida caused significant increase in activities of chymotrypsin inhibitors (CI) and trypsin inhibitors (TI) and the change extent differed among the three treatments (two JA treatments and one damage treatment by A. pallida) (P<0.05). Activities of CI and TI increased 96% and 128%, respectively, in wolfberry leaves treated with 0.1 mmol/L JA, and 94% and 122%, respectively, in wolfberry leaves damaged by A. pallida. The polysaccharide content in wolfberry leaves treated with JA or gall mite reduced significantly (P<0.05), and the reduction was related with the JA concentrations, the higher the JA concentration, the less polysaccharide content. The xylogen content increased significantly in wolfberry leaves treated by 0.1 mmol/L JA, gall mite and 0.001 mmol/L JA (P<0.05), and reached the peak at 5 d after treatment, which increased by 70%, 41% and 36%, respectively. The activities of SOD and PAL increased significantly in wolfberry leaves treated by JA or gall mite (P<0.05), and also reached the peak at 5 d after treatment. The SOD activity in wolfberry leaves treated with 0.1 mmol/L JA increased from 70.77 to 128.98 U, and PAL activity from 10.91 to 20.59 U at 5 d after 0.01 mmol/L JA treatment. The activities of both enzymes decreased at 10 d after 0.01 mmol/L JA treatment but still higher than that of the control. These results suggest that both exogenous JA treatment and gall mite damage could induce defense responses in wolfberry, which are concentration- and time-dependent.

Key words: Wolfberry, Lycium barbarum, defense response, jasmonic acid, gall mite, protease inhibitor, xylogen, polysaccharide