Transcriptome Analysis Unveils Molecular Mechanisms of Acaricide Resistance in Two-Spotted Spider Mite Populations on Hops

Broad-spectrum crop protection technologies, such as abamectin and bifenthrin, are globally relied upon to curb the existential threats from economic crop pests such as the generalist herbivore Tetranychus urticae Koch (TSSM). However, the rising cost of discovering and registering new acaricides, particularly for specialty crops, along with the increasing risk of pesticide resistance development, underscores the urgent need to preserve the efficacy of currently registered acaricides. This study examined the overall genetic mechanism underlying adaptation to abamectin and bifenthrin in T. urticae populations from commercial hop fields in the Pacific Northwestern region of the USA. A transcriptomic study was conducted using four populations (susceptible, abamectin-resistant, and two bifenthrin-resistant populations). Differential gene expression analysis revealed a notable disparity, with significantly more downregulated genes than upregulated genes in both resistant populations. Gene ontology enrichment analysis revealed a striking consistency among all three resistant populations, with downregulated genes predominately associated with chitin metabolism. In contrast, upregulated genes in the resistant populations were linked to biological processes, such as peptidase activity and oxidoreductase activity. Proteolytic activity by peptidase enzymes in abamectin- and bifenthrin-resistant TSSM populations may suggest their involvement in acaricide metabolism. These findings provide valuable insights into the molecular mechanisms underlying acaricide resistance in the TSSM. This knowledge can be utilized to develop innovative pesticides and molecular diagnostic tools for effectively monitoring and managing resistant TSSM populations.