In vitro and in planta antagonistic effects of plant growth-promoting rhizobacteria consortium against soilborne plant pathogens of Solanum tuberosum and Solanum lycopersicum

Potatoes (Solanum tuberosum L.) and tomatoes (Solanum lycopersicum L.), among the main crops belonging to the Solanaceae family, are attacked by several pathogens. Among them Fusarium oxysporum f. sp. radicis-lycopersici and Rhizoctonia solani are very common and cause significant losses. Four plant growth-promoting rhizobacteria, Azospirillum brasilense, Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae and Burkholderia ambifaria were tested against these pathogens. In vitro antagonistic activities of single strains were assessed through dual culture plates. Strains showing antagonistic activity (G. diazotrophicus, H. seropedicae and B. ambifaria) were combined and, after an in vitro confirmation, the consortium was applied on S. lycopersicum and S. tuberosum in a greenhouse pot experiment. The bioprotection was assessed in pre-emergence (infection before germination) and post-emergence (infection after germination). The consortium was able to successfully counteract the infection of both F. oxysporum and R. solani, allowing a regular development of plants. The biocontrol of the fungal pathogens was highlighted both in pre-emergence and post-emergence conditions. This selected consortium could be a valid alternative to agrochemicals and could be exploited as biocontrol agent to counteract losses due to these pathogenic fungi.