Quorum-quenching halotolerant bacteria as biocontrol agents against potato phytopathogens.

Potato is highly susceptible to phytopathogens such as Dickeya solani, Pectobacterium atrosepticum and P. carotovorum, which cause an oxidative stress in the vegetal tissues, promote necrosis, and ultimately compromise postharvest quality. In many Gram-negative bacteria, virulence is regulated by quorum sensing (QS) via N-acyl homoserine lactones (AHLs). Quorum quenching (QQ), the enzymatic degradation of AHLs, has emerged as a promising biocontrol strategy. This study evaluated the biocontrol potential of two halotolerant bacterial strains, Pseudomonas kilonensis B34 and Psychrobacter sp. B38, capable of partially degraded AHLs produced by these phytopathogens. Co-cultures of these QQ strains with the mentioned pathogens significantly reduced tissue maceration in potato tubers, with strongest protective effect observed against D. solani. Under this biotic stress, both strains enhanced antioxidant defense responses in potato tissues, with strain B38 demonstrating the highest effectiveness. This protection was related with higher levels of phenolic compounds, which supported the antioxidant machinery and preserved tissue integrity. Overall, these results highlight the potential of halotolerant QQ bacteria as efficient biocontrol agents and sustainable alternatives to chemical treatments in potato disease management.