De novo transcriptomics based identification and characterization of genes involved in spinosad resistance in the egg parasitoid, Trichogramma chilonis Ishii

<i>Trichogramma chilonis</i> (Hymenoptera: Trichogrammatidae), an effective egg parasitoid, commonly used as an innundative biocontrol agent for the management of many lepidopteron pests worldwide. However, its biocontrol potential is severely hampered due to application of broad spectrum of insecticides against insect pests on different crops. Therefore, development of an insecticide tolerant <i>T. chilonis </i>would be very useful and compatible with chemical control to manage the insect pests under insecticide stressed conditions especially in Integrated Pest management Programmes. Furthermore such strategy would reduce the pesticide load on the crops and would protect the non target organisms. Therefore, a spinosad (45% SC) resistant <i>T. chilonis</i> was selected by continuously exposing to the spinosad for 35 generations and its dosage mortality and quantification of detoxifying enxymes viz., glutathione S-transferases and cytochrome p-450 monooxygenases was done in comparison with susceptible laboratory strain. Furthermore, the spinosad susceptible and resistance strain of T. chilonis were sequenced using high throughput RNA sequencing with the aim to identify the molecular mechanism associated with spinosad resistance. <i>De novo </i>transcriptome analysis showed 1026 differentially expressed genes including 654 and 332 up and down-regulated genes, respectively in the spinosad resistant strain of <i>T. chilonis</i>. Multiple transcripts were associated with already known insecticide targets including cuticle, oxidative phosphorylation and metabolic process. qRT-PCR analysis of 10 differentially expressed genes confirmed the pattern observed in the transcriptome sequencing expression profiles. These finding provide a valuable resource for future studies into the molecular mechanisms underlying insecticide resistance in biocontrol agents like parasitoids and predators.