Crown gall disease of grapevine caused by Agrobacterium tumefaciens, often results in severe economic loss to grape production worldwide damage in vineyards. In this study, the ability of the endophytic bacteria Pseudomonas sp. Sn48, Pantoea sp. Sa14 isolated from domesticated and wild grapevines to induce resistance at both above- and below-ground tissues of grapevines infected with Agrobacterium tumefaciens was demonstrated. Our results provide evidence that both strains can colonize roots and/or shoots. We showed that the strains Pseudomonas sp. Sn48 and Pantoea sp. Sa14 are capable of inducing stilbenic phytoalexin production in grapevine tissues and to further prime plantlets for enhanced phytoalexin production after A. tumefaciens inoculation. We also showed that in the majority of treatments, polyamine accumulation remained unchanged or slightly increased in plantlets treated with strains Pseudomonas sp. Sn48 and Pantoea sp. Sa14 compared with the control. Our findings indicated that the levels of polyamines remained unchanged or significantly decreased in plantlets treated with endophytic bacteria after A. tumefaciens challenge compared to the control and plantlets treated with individual endophytic bacterial strains. PR1, PR2 and PR4 gene expression levels of plantlets treated by Pseudomonas sp. Sn48 and Pantoea sp. Sa14 significantly increased after A. tumefaciens inoculation. Overall, the findings revealed the efficacy of the selected endophytic bacteria in triggering grapevine resistance against A. tumefaciens and the possible use of these strains as an alternative to chemical control methods safe tool in grapevine crown gall disease management.
