Abstract: 【Aim】 The two-spotted spider mite, Tetranychus urticae Koch is an important pest on many agricultural crops worldwide. This study aims to understand the current abamectin resistance and the mutation frequency and expression change of resistance-related genes in different field populations of T. urticae in China. 【Methods】 The resistance of eight field populations of T. urticae to abamectin was determined by vial-leaf dipping (VLD) method, and the gene mutation frequency related to abamectin resistance was detected and the expression levels of genes likely related to abamectin resistance in highly resistant populations were determined by quantitative RT-PCR technique. 【Results】 All the eight field populations of T. urticae tested developed resistance to abamectin. Extremely high resistance to abamectin was found in the populations from Miyun, Beijing (MY-BJ), Weifang, Shandong (WF-SD), Sanya, Hainan (SY-HN), and Changsha, Hunan (CS-HN), with the resistance ratios of 1 526.75-, 481.00-, 315.25-, and 160.75-fold, respectively. In the populations from Tongxian, Beijing (TX-BJ), Haidian, Beijing (HD-BJ), Yuncheng, Shanxi (YC-SX), and Tai’an, Shandong (TA-SD), high resistance was observed with the resistance ratios ranging from 54.38- to 136.38-fold. The mutation frequency of the glutamate-gated chloride ion channel gene GluCl related to abamectin resistance differed in the eight field populations. The highest and lowest mutation frequencies were found in MY-BJ (91.7%) and YC-SX (13.3%) populations, respectively, while moderate mutation frequencies were found in WF-SD and SY-HN populations. There was a significantly positive correlation between resistance level and the mutation frequency of GluCl (P<0.05). The expression levels of GluCl and γ-aminobutyric acid receptor gene (GABAR) in the resistant populations decreased significantly as compared with those in the relatively susceptible strain. 【Conclusion】 Abamectin resistance exists widely in field populations of T. urticae in China. Resistance-related genes with point mutation and the decreased expression are likely relevant to resistance development. Abamectin should be avoided to be applied in controlling T. urticae in fields.

Key words: Tetranychus urticae; abamectin, insecticide resistance, resistance-related gene, gene expression