Gossypol-induced fitness gain and increased resistance to deltamethrin in beet armyworm, Spodoptera exigua (Hübner).

BACKGROUND: In plant-insect interactions, phytotoxins such as gossypol, exert a defensive role on behalf of the plant by interfering with the essential metabolic, biochemical and physiological pathways of herbivorous insects. The beet armyworm, Spodoptera exigua (Hübner), is a key pest for many important crops including a range of vegetables, ornamentals, and cotton. For this study we investigated how resistance to deltamethrin relates to enzyme activity in gossypol-pretreated larvae of S. exigua.

RESULTS: Through selection with deltamethrin insecticides on gossypol-pretreated larvae for 10 generations, the Gos-SEL population developed a 113.29-fold resistance. Under the same conditions the Delta-SEL selected population showed a 69.76-fold increase resistance along with corresponding levels of xenobiotic defense enzymes activity. Similarly, the fecundity of the Delta-SEL population along with male and female longevity were found to be significantly lower when compared to the Gos-SEL population and the lab susceptible-strain group (SS-strain). In addition, the activities of cytochrome P450s in S. exigua were significantly enhanced when the insects were fed on a deltamethrin and gossypol-pretreated diet compared with being fed on deltamethrin alone.

CONCLUSION: The reproductive capacity of S. exigua is significantly reduced in the Delta-SEL and Gos-SEL populations compared to the control group (SS-strain). Elevation of the major detoxification enzyme cytochrome P450 monooxygenase and esterase might play an important role to induce tolerance to the deltamethrin in gossypol-fed S. exigua populations. This study enhances our understanding of detoxification enzyme pathways for S. exigua gene expression and their role in responses to insecticides and plant secondary metabolites. This article is protected by copyright. All rights reserved.