Streptomyces sp. G21 mitigates postharvest mango anthracnose by tuning ROS and phenylpropanoid metabolism

Mango (Mangifera indica L.), a tropical fruit of significant economic importance, is highly susceptible to postharvest infections by pathogenic microorganisms, leading to substantial quality deterioration. This study explored the biocontrol efficacy of Streptomyces sp. G21, previously identified as an antagonist against Colletotrichum gloeosporioides, the causal agent of mango anthracnose. Results showed that treatment with G21 significantly enhanced disease resistance in mango fruits, as evidenced by a reduced disease index. Moreover, G21 application delayed the decline in key storage quality parameters, including firmness, titratable acid, ascorbic acid and total phenol content. Mechanistically, G21 treatment enhanced the activity of defense-related enzymes (SOD, CAT, POD) and the expression of their corresponding genes (POD,PAL, 4CL), while reducing ROS accumulation and mitigating membrane lipid peroxidation. Further study showed that G21 modulated the synthesis and enrichment of phenylpropanoid-like compounds, thereby contributing to enhanced disease resistance. Correlation analysis identified MiPAL6 and Mi4CL-like9 as potential regulatory candidates mediating G21-induced resistance. These findings demonstrate that Streptomyces sp. G21 has potential as a biological control agent for maintaining mango storage quality and reducing postharvest disease incidence, offering a promising strategy for sustainable disease management.