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The codling moth, Cydia pomonella, is a major pest of apple and pear orchards. However, with intensive use of pesticide, an increasing number of resistances has been reported. Detoxification is one of the main mechanisms involved in resistance in Lepidoptera, and there is still much to discover about the molecular mechanisms underlying it. This study was conducted to decipher the molecular mechanisms involved in the insecticide resistance of C. pomonella and to identify genetic markers associated with resistance upon exposure to several pesticides. To that aim, an experimental evolution was carried out from a wild population resistant to several active substances. We generated three lines by combining genetic crosses and experimental selection using chlorantraniliprole, deltamethrin and spinosad. High throughput RNA-sequencing (RNA-seq) was performed on the three lines to verify whether similar mechanisms were involved in pesticide resistance across lines and to assess the role of detoxification and other mechanisms in resistance. In total, we found 592 mutations and 157 differentially expressed genes. Of the candidate genes identified as involved in resistance, a very limited number were shared between lines. We found in total 20 genes belonging to already known candidate genes, with 2 of them known to be involved in C. pomonella resistance (CYP4C1 and CYP6B2) and identified several genes that have never been linked with resistance before (mainly associated with odorant perception and stress). [ABSTRACT FROM AUTHOR]

As temperature is expected to strongly increase in the future, understanding temperature-mediated toxicity of insecticides is determinant to assess pest management efficiency in a warming world. Investigating molecular and biochemical mechanisms associated with cross mechanisms of temperature and insecticides on pests' tolerance would also be useful in this context. This study aimed to investigate cross effects between temperature and insecticides on the survival of a major pest, the codling moth Cydia pomonella , and their underlying mechanisms. The effect of three insecticidal active ingredients, i.e. chlorantraniliprole, emamectin and spinosad, was assessed at different temperatures on: (i) C. pomonella larval survival; (ii) detoxification enzymes activities (cytochrome P450 multi-function oxygenases, carboxylesterases and glutathione S-transferases) and (iii) genes expression of some detoxification enzymes, heat shock proteins and receptors targeted by the insecticides. We observed a decreased efficiency of emamectin and spinosad at high temperature to control the codling moth while no influence of temperature on chlorantraniliprole efficacy was observed. Detoxification enzymes activities were improved by heat stress alone but not by double stress (temperature + insecticides). Moreover, two detoxification genes (Cyp9A61 and Gst1) were over-expressed by a single stress but not by two stresses while Hsp70 and Cyp6B2 genes may be involved in tolerance to two stresses in C. pomonella. These results confirmed the cross effects of temperature and insecticides on C. pomonella for emamectin and spinosad and provided clues to understand how temperature affects the susceptibility of C. pomonella to insecticides. They illustrate however the complexity of molecular and biochemical responses of individuals facing multiple stresses. [Display omitted] • Evidence of cross effects of temperature and insecticides on C. pomonella mortality. • Some active ingredients efficiency on C. pomonella are affected by high temperature. • Molecular and biochemical responses of codling moth facing one or two stresses. [ABSTRACT FROM AUTHOR]