Grey mould caused by Botrytis cinerea is among the most important disease affecting the production of grapevine worldwide. The high economical loss each year has led producers to become more dependent on chemical pesticides for protection. However, environmental impacts of the pesticides overuse have sparked crescent interest in developing alternative biocontrol methods. The use of plant-associated bacteria has, thus, received many attentions as a promising strategy for sustainable agriculture. Three strains, isolated from the rhizosphere of crops cultivated in the northeast of France, were evaluated for their antagonistic effect. They were found to exhibit an antagonistic effect against a set of phytopathogenic fungi. Phenotypic and molecular characterization showed that isolates belong to the genus Burkholderia. The genome sequencing and analysis of isolated strains revealed the presence of gene clusters coding for secondary metabolites potentially involved in the biocontrol. When the grapevine plantlets were infected with B. cinerea, all plants associated with isolated strains showed a significant protection against B. cinerea compared to non-inoculated plants. To understand the mechanisms contributing to the biocontrol effect of selected isolates, the production of reactive oxygen species (ROS) and the expression of several defense genes were investigated. The maximum accumulation of H2O2 was detected in the inoculated cell suspension medium 30 min after the challenge with B. cinerea. After pathogen challenge, results showed that grapevine cell culture inoculated with isolated strains exhibited significant over expression of defense markers genes PR5, PR10, and chit4c, in response to B. cinerea, confirming their priming effect.
Keywords: Biocontrol; Burkholderia; Grapevine; Grey mould; Rhizosphere.