Revitalizing copper's efficacy: Using carvacrol to overcome copper tolerance in Pectobacterium carotovorum subsp. carotovorum for enhanced prevention of soft rot disease during crop storage

•Carvacrol improved the susceptibility of copper tolerance Pcc (CTP) to copper.•The combination of carvacrol and copper increased antibacterial activity by inhibiting copper-tolerant and biofilm-related genes.•The combination can effectively diminish the rotted tissues on detached vegetables used by copper tolerance Pcc (CTP). The phytopathogen Pectobacterium carotovorum subsp. carotovorum (Pcc) is a major causal agent of soft rot disease in various vegetables, leading to substantial pre- and post-harvest losses in agriculture. Moreover, the emergence of copper-tolerant Pcc strain is increasingly threatening the efficacy of copper sulfate treatments to control soft rot. Here, we investigated the impact of carvacrol, copper sulfate and their combination application on a copper-tolerant strain of Pcc (CTP). The results showed that the minimum inhibitory concentrations (MIC) for copper sulfate and carvacrol against CTP was 500 and 200 µL/L, respectively. Notably, the combination of these chemical agents significantly enhanced their antibacterial efficacy, reducing the MIC to 140 µL/L. In follow-up control tests using detached potatoes, Chinese cabbage leaves and onions, the carvacrol-copper combination reduced the severity of soft rot and this treatment strongly affected the biofilm produced by CTP, with minimum biofilm inhibition concentration (MBIC) and minimum biofilm eradication concentration (MBEC) values of 250 and 500 µL/L, respectively. The scanning electronic microscopy (SEM) and confocal laser scanning microscopy (CLSM) results confirmed the structural deformations and disruptions of CTP's biofilm under the carvacrol-copper sulfate treatment combination. Furthermore, the transcriptomic analyses and RT-qPCR validation revealed the significant down-regulation of genes associated with CTP's motility, biofilm formation, and copper tolerance after its exposure to carvacrol. Altogether, our findings demonstrate that carvacrol impairs biofilm formation in CTP, thus reducing its copper tolerance and restoring its sensitivity to copper sulfate. This comprehensive study is the first to report on the potential of carvacrol to enhance copper sensitivity in CTP and diminish its copper tolerance, offering a novel approach to managing copper-tolerant phytopathogens in agriculture. [Display omitted]