Inheritance of acaricide resistance in inbreeding lines of two-spotted spider mite
Background: The two-spotted spider mite is one of the economically important crop pests. Its control has been and still is largely based on the use of acaricides. However, due to its short life cycle and abundant progeny it is able to develop resistance to acaricides very rapidly. The information on mechanisms of resistance is the aim of devising resistance management strategies. Materials and methods: A laboratory-selected susceptible and resistant inbreeding lines of the spider mite Tetranychus urticae Koch. were used to determine toxicological, cross-resistance, biochemical and genetic data. Mortality caused by acaricide in the F1 progeny and backcrosses with F1 females revealed striking differences in the mode of inheritance. Results: The resistance ratio (RR) calculated from the LC50s of selected susceptible and resistant to dimethoate, bifenthrin, abamectin and bromopropylate lines were 1000, 2600, 2000 and 2000-fold, respectively. Resistance to dimethoate is monogenic dominant inheritance associated with a strong increase in isoenzyme carboxylesterase activity and that could be considered as biochemical marker. Mortality caused by selecting by abamectin in the F1 and backcross progeny indicated that the mode of inheritance resistance is dominant digenic and by selecting bifenthrin and bromopropylate was incompletely recessive linked with two main genetic mutations. Conclusion: The biochemical/physiological mechanisms of resistance to acaricides can be categorized as target site insensitivity or regulatory changes in gene expression elevated some enzyme activity that determines the degree viability in arthropods.