Antagonistic activity against Verticillium dahliae of the endophytic bacterial strains isolated from the xylem of olive trees

Nature Conferences (Harnessing the Plant Microbiome), Virtual Conference, October 22-24, 2021.
Olive is one of the most important cultivated trees in the Mediterranean Basin and exhibits a wide range of noteworthy environmental attributes. Nowadays, however, its health status is seriously threatened by phytopathogenic organisms such as the fungus Verticillium dahliae and the bacterium Xylella fastidiosa that obstruct xylem sap flow leading to wilting of plant tissues. Biological control agents represent a promising strategy to control these plant pathogens. We investigated the potential of xylem-inhabiting microorganisms that may compete for infection sites, antagonize the pathogen, and/or induce host plant defense responses, thus contributing to mitigate disease development. A total of 108 bacterial strains isolated from xylem vessels of different cultivated and wild olive genotypes were used to test their antagonistic activity against three Verticillium dahliae strains isolated from olive (defoliating and non-defoliating strains) and tomato. Antagonistic activity was tested in olive xylem sap and in three predefined culture media with chemical composition similar to that of olive xy lem sap, using a high-throughput fungal-bacterial interaction screen method. Results based on a Relative Growth Index indicated that 29 strains restrict V. dahliae (RGI0.2), while 27 strains are neutral regarding V. dahliae (-0.05
Supported by Projects XF-ACTORS 727987 (EU-H2020), AGL2016-75606-R, and PID2020-114917RB-I00 (AEI-MICINN Spain and FEDER-EU)