Invasive Species Compendium

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Abstract Full Text

Effects of host plants on activities of three groups of enzymes in Spodoptera frugiperda (Smith)larvae.

Abstract

Objective: To clarify the effects of different host plants on activities of threegroups of enzymes (digestive enzymes, protective enzymes and detoxification enzymes) in fall armyworm (FAW), Spodoptera frugiferda (Smith) larvae, and provide theoretical basis for further study on host selection and adaptation mechanism of S. frugiferda Method: Leaves of four host plants, including maize, wheat, potato and tobacco, were used to feed FAW larvae from the 1st instar to the 5th instar, and the activities of digestive enzymes (lipase, pepsin, and α-amylase), protective enzymes superoxide dismutase(SOD), peroxidase(POD), and catalase(CAT) and detoxification enzymes glutathione S-transferase(GST), carboxylesterase(CarE), multifunctional oxidase(MFO), cytochrome P450(CYP450) in the 5th instar of S. frugiperda were determined. The secondary metabolites(total phenols, tannins, flavonoids)and nutrients substance(soluble sugars, soluble proteins)content in the four host plant leaves were tested, and the correlation between enzyme activities in FAW larvae and the contents of secondary metabolites and nutrients in host plants was analyzed. Result: The activities of lipase and pepsin inlarvae fed on potato leaves were higher or significantly higher than those in larvae fed on the other three host plant leaves(P<0.05, the same below), while the α-amylase activity in larvae fed on tobacco leaves(0.48±0.08 U/mg) was highest, which was significantly higher thanlarvae fed onother three host plants. The activities of SOD and POD in larvae fed on potato leaves were significantly higher than those in larvae fed on the other three host plant leaves. The CAT activity(225.54±51.56 U/mg)in larvae fed on tobacco leaves was the highest, which was as 2.71 times as that in larvae fed on maize;the activities of GST, CYP450 and MFO in larvae fed on potato and tobacco leaves were higher than those in larvae fed on maize and wheat leaves, the GST activity in larvae fed on potato and tobacco leaves(100.50±4.71 U/mg and 98.69±6.21 U/mg)were significantly higher than in larvae fed on maize and wheat leaves(54.85±1.94 U/mg and 70.62±4.04 U/mg). The activity of CarE was the highest in larvae that fed on tobacco leaves(184.79±9.05 U/g). The contents of total phenols,tannins, and flavonoids in the four host plant leaves werethe highest in potato, followed by corn and wheat, and werethe lowest in tobacco. The soluble sugar content was the highest in wheat leaves(18.65±1.08 mg/g), and the soluble protein content was the highest in potato leaves(306.30±29.07 mg/g), soluble sugar content were soluble protein content were the lowest in tobacco leaves. Pearson's linear correlation coefficient indicated that some of the activities of digestive and protective enzymes in S. frugiperda larvae fed on different host plants were significantly related to the content of host plant nutrients and secondary metabolites. Conclusion: S. frugiperda shows strong physiological plasticity on different host plants. Its larvae may increase the activities of digestive enzymes to absorb as much nutrition as possible from plants, and regulate activities of protective and detoxification enzymes to increase the adaptability to secondary metabolites and toxin substances in host plants. The larvae flexible adaptation ability may be an important reason for the wide range of host plants.