Biochemical and molecular dynamics of metabolic flux and detoxification responses in phosphine‐resistant <i>Tribolium castaneum</i>

Abstract Phosphine (PH 3 ) remains the principal fumigant for the protection of stored grains; however, the widespread occurrence of PH 3 ‐resistant Tribolium castaneum has become a major constraint to its long‐term efficacy. Although alterations in metabolic and detoxification processes have been associated with PH 3 resistance, their coordinated biochemical and molecular responses across geographically distinct populations remain insufficiently understood. This study investigated metabolic and detoxification responses in PH 3 ‐resistant T. castaneum populations by integrating PH 3 bioassays, Bayesian hierarchical modelling, enzyme activity assays, quantitative gene expression analysis and multivariate statistical approaches. Bayesian analysis revealed substantial population‐level variation in PH 3 susceptibility, with resistance ranging from weak to very strong among field populations. Resistant populations consistently exhibited altered glycolytic enzyme profiles, characterized by reduced glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) activity and enhanced triose phosphate isomerase (TPI) activity and transcript abundance, suggesting modulation of energy metabolism under PH 3 stress. Detoxification responses were characterized by elevated carboxylesterase (CE) and glutathione S‐transferase (GST) activities together with increased expression of CE and GST Delta family genes, whereas acetylcholinesterase (AChE) activity remained unchanged despite marked transcriptional induction. Correlation and principal component analyses demonstrated strong concordance between biochemical and transcriptional datasets, indicating coordinated physiological responses across resistant populations. Overall, this study extends current knowledge by providing an integrated biochemical and molecular characterisation of metabolic and detoxification responses associated with PH 3 ‐resistant T. castaneum . These findings improve our understanding of insect responses to fumigant stress and provide a foundation for future functional studies and resistance‐monitoring strategies.