Influence of peel morphology on pesticide distribution and metabolic responses in mango after postharvest immersion treatment.

Pesticide residues in agricultural products pose substantial food safety challenges, necessitating an improved understanding of pesticide behavior for optimized application. We examined the residue distribution patterns and metabolic responses of two non-systemic pesticides (thiram and tolfenpyrad) and three systemic ones (pyriproxyfen, pyraclostrobin, and tebuconazole) in two mango cultivars with distinct peel characteristics, thick-peel R2E2 and thin-peel Guifei, following postharvest immersion. The results demonstrated that peel morphology, fruit maturity, and pesticide properties collectively govern migration behavior, with thick-peel R2E2 exhibiting significantly lower penetration compared to thin-peel Guifei. Systemic pesticides accumulated 1.32-1.86 times more extensively in Guifei than in R2E2 after 9 h, whereas fruit maturity enhanced migration, increasing residues by 1.27-3.14 times in Guifei and 1.04-2.76 times in R2E2. All systemic pesticides displayed consistent spatial distribution, with peduncle residues exceeding apex levels by 1.27-3.84 times. This difference is attributable to structural differences wherein peduncle regions with dense vascular bundles, elevated crude fiber, and soluble solids promoted accumulation, whereas apex regions with high vitamin C and total sugar contents facilitated metabolic compensation. Metabolomic profiling identified the activation of key defense pathways, including glycolysis, tricarboxylic acid cycle, and flavonoid biosynthesis, establishing integrated energy compensation and antioxidant mechanisms. These findings elucidate the spatially distinct metabolic and defense adaptations in mangoes under pesticide stress and provide a scientific foundation for optimized pesticide management and enhanced food safety protocols.