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14th International Conference on Microbial Interactions & Microbial Ecology

Vienna, Austria

Francesca Brescia

Research and Innovation Centre, Fondazione Edmund Mach (FEM), Italy

Title: Pseudomonas spp. strains isolated from grapevine leaves modulate the inhibitory activity of the biocontrol agent Lysobacter capsici AZ78


Biography: Francesca Brescia


Statement of the Problem: Bacterial biocontrol agents can improve plant heath with various mechanisms. The bacterial genus Lysobacter includes different species producing compounds and lytic enzymes active against phytopathogenic microorganisms and therefore can be a source of new biocontrol agents. In particular, L. capsici AZ78 (AZ78), isolated from tobacco rhizosphere, effectively controls the causal agent of grapevine downy mildew (Plasmopara viticola), thanks to the production of antibiotics. Since bacterial communities might modulate the antibiotic production of biocontrol agents, the aim of this research was to understand if grapevine phyllosphere bacteria could affect the antibiotic production of AZ78. To test the hypothesis we used a simplified model system with a culturable phytopathogenic oomycete (Pythium ultimum).

Methodology & Theoretical Orientation: 47 bacterial strains were isolated from leaves of Vitis vinifera L. cv. Pinot gris and Goldtraminer, identified by 16S rDNA phylogenetic analysis and their impact on AZ78’s inhibitory activity was assessed in vitro according to the experimental design described in Figure 1.

Findings: Most of the Gram-negative bacterial isolates were γ-Proteobacteria, while the Gram-positive isolates belonged to Actinobacteria and Firmicutes. None of the isolated strains showed an inhibitory activity against P. ultimum. Interestingly, most of them promoted AZ78 inhibitory activity. In particular Pseudomonas sp. L35 increased AZ78 inhibitory activity of the 29.6±0.95%, this can be related to a change in AZ78 gene expression triggered by the presence of the strain.

Conclusion & Significance: The interaction with the natural microbiota is an important factor to be considered in evaluating biocontrol agent’s efficacy, because their inhibitory activity can be affected by the microbiota itself. To gain a full picture, additional studies are necessary, taking into account the plant response, as well as considering the variation in AZ78 gene expression.