Transgenerational phenotypic plasticity of the two-spotted spider mite (Tetranychus urticae Koch) in response to abamectin.

Tetranychus urticae Koch, commonly known as the two-spotted spider mite, is a serious threat to many crop species. This species can rapidly develop resistance to acaricides, rendering chemical control of the mite extremely difficult. In the present study, a homozygous mite population of T. urticae was established, and the potential involvement of transgenerational phenotypic plasticity in the development of resistance to the acaricide abamectin was investigated. The mite methylome was analyzed for the first time to evaluate the possible role of this epigenetic mark in the observed response to abamectin. The results showed a significant maladaptive transgenerational phenotypic response. Mites, previously exposed to abamectin treatments for seven consecutive generations, showed lower acaricide resistance compared to mites that were never treated with abamectin. This phenotype persisted for two consecutive generations after the termination of abamectin exposure. Methylome analysis of treated and untreated mite groups revealed that this species possessed an extremely low level of cytosine methylation, if any, suggesting that this epigenetic mark is unlikely to be involved in the transgenerational response. Overall, the results show that transgenerational phenotypic plasticity can significantly modify the phenotype of T. urticae. However, under the conditions tested, transgenerational phenotypic plasticity is not directly involved in the development of abamectin resistance. Further work is needed to better understand how transgenerational phenotypes are involved in the response of T. urticae to acaricides.