Defense enzyme activity of dallisgrass in response to grasshopper feeding

Defense enzymes are potential defense mechanisms against herbivorous insects in plants. It is important to learn about the changes in protective enzymes in response to insect-induced stresses in excellent forages, such as dallisgrass (Paspalum dilatatum). In the present study, total antioxidant capacity (T-AOC), peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), tyrosine ammonia-lyase (TAL), lipoxygenase (LOX), polyphenol oxidase (PPO), glutathione S-transferase (GST), and phenylalanine ammonia-lyase (PAL), as well as total phenol (TP) content of dallisgrass were investigated at 0, 24, 48, 72, and 96 h after grasshopper (Oxya chinensis) feeding. The results showed that the activities of POD, LOX, CAT, PPO, TAL, and GST as well as the TP content in dallisgrass were significantly increased after grasshopper feeding compared with the control (P < 0.05). T-AOC increased significantly 24 h after feeding (P < 0.05). Moreover, the activities of PPO, TAL, and GST first increased and then decreased over time. At 48, 72, and 24 h of treatment, the activity of TAL, PPO, and GST peaked at 3.71, 2.10 and 21.25 times of CK, respectively. In contrast, grasshopper feeding significantly reduced the activity of SOD and PAL (P < 0.05). Overall, it could be speculated that protective enzymes such as POD, CAT, PPO, TAL, GST, and LOX play very important protective roles against insect herbivores.