Application of microbial cocktails from olive oil mill sludge to promote plant health and welfare

The main objective of this work was the physicochemical and microbiological characterization of Olive Mill Waste sludge (OMWs) to develop strategies aimed at increasing plant well-being and phytoprotection. Eighteen strains were tested in vitro for their ability to suppress pathogens such as Botrytis cinerea, Fusarium oxysporum f. sp. melonis, Xanthomonas campestris and Clavibacter michiganensis subsp. michiganensis. Among them, three microbial strains with promising antagonistic activity were selected for further analysis. These strains also improved seedling germination and increased root weight through biopriming. The selected strains were identified as Bacillus wiedmannii (OR-BS-1), Aspergillus terreus (OR-HS-2) and Penicillium paneum (OR-HS-6) and were tested in vivo as a microbial cocktail. The microbial cocktail caused phytostimulant activity in seedlings and a notable protective effect against fungal phytopathogens, though results varied depending on the pathosystem. These findings highlight the importance of revaluing OMWs as a source of beneficial microorganisms, contributing to a more sustainable agriculture.