Biocontrol Potential of an Endophytic Strain against the Grapevine Trunk Disease Pathogen and Its Mechanism of Action.

Grapevine trunk diseases (GTDs) impact the sustainability of vineyards worldwide and management options are currently limited. Biological control agents (BCAs) may offer a viable alternative for disease control. With an aim to develop an effective biocontrol strategy against the GTD pathogen , this study investigated the following: (1) the efficacy of the strains in suppressing the BD pathogen in detached canes and potted vines; (2) the ability of a strain of (BCA17) to colonize and persist within grapevine tissues; and (3) the mode of action of BCA17 to antagonize . Co-inoculations of the antagonistic bacterial strains with revealed that one strain of (BCA17) suppressed infection by 100% and 80% in detached canes and potted vines, respectively. Stem inoculations of a laboratory-generated rifampicin-resistant strain of BCA17 in potted vines (cv. Shiraz) indicated the bacterial strain could colonize and persist in the grapevine tissues, potentially providing some protection against GTDs for up to 6 months. The bioactive diffusible compounds secreted by BCA17 significantly reduced the spore germination and fungal biomass of and the other representative GTD pathogens. Complementary analysis via MALDI-TOF revealed the presence of an unknown cyclic lipopeptide in the bioactive diffusible compounds, which was absent in a non-antagonistic strain of (JMN13), suggesting this novel lipopeptide may be responsible for the biocontrol activity of the BCA17. Our study provided evidence that BCA17 is a potential BCA to combat , with a potential novel mode of action.