Forest tree extracts induce resistance to Pseudomonas syringae pv. tomato in Arabidopsis

The widespread use of conventional pesticides for plant pathogen control poses significant risks to human health and the environment, and it is therefore crucial to develop environmentally friendly, human-safe alternatives to these products that offer a sustainable approach for crop protection. Here, we examined the potential of ethanolic extracts from four forest tree species for their antibacterial activity against the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) and their ability to trigger effective defense responses in the model plant Arabidopsis thaliana. The extracts exhibited direct toxic effects against Pst and triggered the expression of defense-related genes naturally induced by oxidative stress cues or the defense elicitor salicylic acid in leaf tissue. The direct antibacterial effects of the tree extracts, together with their defense gene-inducing effects in planta, resulted in a strong host plant-protecting effect against Pst. These findings suggest the eventual effectiveness of forest tree extracts as plant protectants against the bacterial pathogen Pst. They also suggest the potential of these extracts as a sustainable, eco-friendly alternative to conventional pesticides for the management of economically important plant pathogens.