Functional analysis of major detoxification gene superfamilies driving flubendiamide resistance in South Indian Tuta absoluta field populations

The tomato pinworm Tuta absoluta (Meyrick), a major pest, has spread worldwide and caused substantial economic losses in tomato cultivation. Repeated insecticide use has resulted in widespread resistance, especially to the diamide insecticide flubendiamide. This study explored the molecular mechanisms underlying flubendiamide resistance in a field population of T. absoluta from South India, focusing on detoxification-related gene families, such as cytochrome P450 monooxygenases (CYP450s), glutathione S-transferases (GSTs), and carboxyl/choline esterases (CCEs). Phylogenetic analysis was performed using 26 gene sequences from T. absoluta and related lepidopteran species. Bioassays revealed that the Krishnagiri (KNG) population is highly resistant, and gene expression analysis was conducted on KNG and susceptible populations treated with sublethal LC₂₅ doses of flubendiamide. Quantitative real-time PCR showed significant overexpression of CYP248f in resistant larvae at 24 and 48 h after treatment, suggesting a role in metabolic detoxification. Among the GSTs, TaGSTe and TaGSTd were notably upregulated, whereas TaGSTs, TaGSTt, and TaGSTz were not differentially expressed. CCE genes (TaCCE1 and TaCCE2) showed no significant expression, indicating a limited role in resistance. Molecular docking supported these findings, showing strong ligand-binding affinities for the overexpressed CYP and GST proteins, highlighting potential molecular targets for resistance monitoring and management.