Abstract: 【Aim】 To investigate the biochemical mechanisms of defense responses of kidney bean to insect herbivory. 【Methods】 The activities of defense enzymes in kidney bean subjected to feeding by the western flower thrips (WFT), Frankliniella occidentalis (Pergande), mechanical wounding, and treatment of exogenous methyl salicylate (MeSA) and jasmonic acid (JA), respectively, were detected. 【Results】 The results showed that the peroxidase (POD) activities in kidney bean subjected to different treatments increased significantly compared to control. The POD activities induced by F. occidentalis feeding and mechanical wounding reached a peak at 72 h, while those induced by JA or MeSA reached a peak at 48 h. The proteinase inhibitor (PI) activities in kidney bean increased most obviously after thrips feeding. The activities of the key enzymes of JA pathway, lipoxygenase (LOX) and polyphenol oxidase (PPO), increased significantly after F. occidentalis feeding, mechanical wounding and JA induction, respectively, while MeSA did not induce their activities. The activities of phenylalnine ammonialyase (PAL), a key enzyme of SA pathway, increased firstly and then decreased in kidney bean subjected to thrips feeding or mechanical wounding. PAL activity induced by MeSA was significantly higher than the control at 24 h after treatment (P<0.05) but was similar to the control at other treatment time. JA induction failed to cause significant changes of PAL activity (P>0.05). Thrips feeding, JA induction, MeSA induction and mechanical wounding caused β-1,3-glucanase (PR-2) activities to increase significantly (P<0.05). 【Conclusion】 These results indicated that different treatments can induce distinct defense responses in kidney bean, and changes in defense enzyme activities are related to treatment types and treating time.

Key words:  Frankliniella occidentalis, kidney bean, insect herbivory, mechanical wounding, jasmonic acid, methyl salicylate, defense enzyme, enzyme activity