Abstract: To evaluate the resistance risk of Panonychus citri to amitraz and clarify the relationship between expression level of cytochrome P450 gene and resistance of P. citri, resistance selection was conducted in the laboratory, and cross-resistance of the amitraz-resistant strain was studied with slide-dip method and cytochrome P450 gene expression profiles between the resistant strain and the susceptible strain were compared using RPKM (reads per kb per million reads) method. After selection with amitraz continuously for 12 generations, a resistant strain was obtained with the resistance ratio (R/S) of 26.32 compared with the susceptible strain. The realized heritability of resistance to amitraz was 0.148. Bioassay data showed that the amitraz-resistant strain had positive cross-resistance to spirodiclofen, diafenthiuron, propargite and azocyclotin (the R/S ratio was 16.85, 4.98, 2.13, and 2.05, respectively), but had no crossresistance to abamectin, fenbutatin oxide, pyridaben and petroleum oil (the R/S ratio was 1.10, 1.21, 0.67 and 0.99, respectively). Gene expression difference analysis results indicated that 16 cytochrome P450 genes were up-regulated and 27 cytochrome P450 genes were down-regulated in the resistant strain. CYP389A6 ［log₂ratio(RS/SS)=11.526］ and CYP389A2 ［log2 ratio(RS/SS) =-12.683］ were the top up-regulated and down-regulated genes, respectively, which are very likely to be associated with the resistance of P. citri to amitraz.

Key words: Panonychus citri, amitraz, cross-resistance, resistant strain, susceptible strain, P450 gene, expression difference