The molecular marker of kdr against fenpropathrin in Tetranychus cinnabarinus

The carmine spider mite, Tetranychus cinnabarinus (Boisduval), is one of the most important pests in agricultural industry. Pyrethroid insecticide has been used to control insects and mites worldwide. However, the intensive use of pyrethroid insecticide resulted in the development of resistance, which has mainly been induced by a variety of point mutations responsible for voltage-gated sodium channel (VGSC) insensitivity and has become the biggest obstacle to sustain the use of pyrethroid insecticide. In this study, we cloned cDNA full length of the para-homologous sodium channel gene from T. cinnabarinus named TC-vgsc. The complete open reading frame of TC-vgsc contains 6,579 nucleotides, encoding 2,193 amino acids. A point mutation, F1538I, was identified from both the DNA and RNA sequences of VGSC in fenpropathrin-resistant strain, which developed approximately 100-folds resistance against fenpropathrin. The result indicated the F1538I kdr mutation underwent DNA mutation events rather than RNA editing. Single nucleotide polymorphisms detection of F1538I mutation from indoor susceptible strain, fenpropathrin-resistant strain, and seven field populations found that this mutation appeared in all the strains (populations), but the frequency of mutation was closely related to the resistance level, with a r2 value of 0.665 (P < 0.05), that is, the higher the resistance level, the larger the mutation frequency. These results demonstrated that the F1538I mutation in the kdr gene can be used as a molecular marker for fenpropathrin-resistance monitoring in field T. cinnabarinus populations.