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Keywords:

  • small brown planthopper;
  • P450;
  • esterases;
  • acetylcholinesterase;
  • semi-quantitative RT-PCR;
  • quantitative real-time RT-PCR;
  • RNAi

Abstract

BACKGROUND

Laboratory selection is often employed in resistance mechanism studies because field-derived populations commonly do not have high enough resistance for such studies. In the present study, a field-collected Laodelphax striatellus population from eastern China was laboratory selected for chlorpyrifos resistance and susceptibility, and the developed strains, along with a field population, were studied for cross-resistance and resistance mechanisms at biochemical and molecular levels.

RESULTS

A 158.58-fold chlorpyrifos-resistant strain (JH-chl) and a chlorpyrifos-susceptible strain (JHS) were established after laboratory selection of 25 generations. Cross-resistance to deltamethrin, diazinon, methomyl, carbosulfan, acephate and imidacloprid were detected in JH-chl and a field-collected strain (JHF). Synergism and enzyme activity data suggested potential involvement of P450s and esterases in JH-chl as well as AChE alteration. Furthermore, CYP6AY3v2, CYP306A2v2, CYP353D1v2 and LSCE36 genes were significantly overexpressed in JH-chl (6.87–12.14-fold). Feeding of dsRNAs reduced the expression of the four target genes (35.6–56.8%) and caused significant adult mortality (75.21–88.45%), implying resistance reduction. However, mechanism(s) conferring chlorpyrifos resistance in JHF were unclear.

CONCLUSION

In contrast to previous reports, multiple overexpressed detoxification genes were potentially associated with chlorpyrifos resistance, as confirmed by RNAi feeding tests. Chlorpyrifos resistance exhibits cross-resistance with insecticides in the same and different classes. © 2013 Society of Chemical Industry