The impact of hot water and salicylic acid treatments on metabolomic changes and defense mechanisms against anthracnose caused by Colletotrichum gloeosporioides in mango fruit

This study evaluated the effects of hot water (HW), salicylic acid (SA), and their combination (HW + SA) on disease suppression, metabolomic alterations, and defense-related responses in ‘Nam Dok Mai Si Thong’ mango (Mangifera indica L.). Fruits were treated with HW (49 °C for 10 min), SA (2 mM for 10 min), or combined HW + SA, inoculated with Colletotrichum gloeosporioides, and stored at 25 °C. We assessed the infection index, metabolomic profiles, total phenolic content (TPC), and activities of superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), chitinase, and β-1,3-glucanase in both peel and pulp. Four days after inoculation, the infection index was significantly reduced by HW (40 %), SA (38 %), and HW + SA (15 %) compared to the control (48 %), with the combined treatment exhibiting the greatest efficacy. The HW + SA treatment significantly decreased disease severity, with infection indices lower than those observed in fruits treated with HW or SA alone. Untargeted metabolomics revealed that the combined HW + SA treatment preserved metabolic features similar to freshly harvested fruit while inducing unique defense-related metabolites, including phenolic compounds, flavonoids, and lipid derivatives. Biochemical assays confirmed that combined HW + SA markedly enhanced TPC and upregulated the activities of defense-related enzymes such as PAL, PPO, POD, SOD, chitinase, and β-1,3-glucanase. These responses were more rapid in the peel and sustained in the pulp, suggesting both local and systemic defense activation. These findings demonstrate that combined HW and SA treatment can effectively regulate anthracnose rot in mango.