Effects of multi-generation feeding with different host plants on activities of enzyme in Spodoptera frugiperda larvae.
To fully understand the impact of multi-generation feeding with different host plants on the activities of enzymes in fall armyworm (FAW), Spadoptera frugiperda larvae, referred to as the leaves of three host plants (maize, wheat and potato) were used as the food for FAW larvae from the first generation to the third generations of 5th instar, and the activities of protective enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), digestive enzymes (lipase, pepsin and a-amylase) and detoxification enzymes glutathione S-transferase (GSTS), carboxylesterase (CarEs) and cytochrome P4508 (CYP4SOS) were determined in the 5th instar of S. frugiperda, the analysis of the correlations among the development, the enzymes activities in FAW larvae and the concentrations of secondary metabolites in host plants were also conducted. The results showed that the larval development duration was longest when fed on potato leaves and shortest fed on wheat leaves, and the difference was significant. The concentrations of total phenols, tannins, flavonoids and alkaloid in the maize and potato leaves were significantly higher than those in wheat. The activities of CAT, POD and SOD in larvae fed on potato leaves were highest, while those in the larvae fed on wheat leaves were lowest. Besides, the POD and SOD activities in larvae fed on potato leaves were 1.34 and 1.26 times higher than those in larvae fed on wheat leaves, while the activities of pepsin in larvae fed on potato leaves (10.502 U/mg. prot) were more than 6.96 times of those in larvae fed on maize leaves (1.508 U/mg. prot), and there was no significant difference in the activities of lipase and x-amylase between FAW that fed on three host plant leaves. Moreover, the activities of CYP450$ in S. frugiperda fed on maize leaves were significantly higher than that fed on wheat and potato leaves, however, the activities of GSTS and CarEs larvae those fed on different host plant leaves had no significant difference. In summary, multi-generation feeding with different host plants may has different concentrations of secondary metabolites, and the activities of enzymes in FAW had changed and the development duration of larvae were different.