Unconventional compounds versus endogenous defence mechanisms against powdery mildew: what drives grapevine phyllobiome composition?

"Under a global changing scenario, the reduction of antimicrobial treatments and the application of eco-friendly compounds is an impelling challenge for grapegrowers in the optic of a more sustainable viticulture. We addressed this research to study if non-conventional compounds can counter leaf powdery mildew attack and how they can influence the phyllobiome of Vitis vinifera 'Moscato' and 'Nebbiolo' plants. The effect of antifungal treatments in shaping the foliar microbial community of powdery mildew-infected vines was evaluated by: i) community-level physiological profiling (CLPP) by using Biolog EcoplatesTM; ii) high throughput sequencing of ITS2 region; iii) depict of virome, viroids and phytoplasma; iiii) analysis of cuticular wax content and secondary metabolites. Independently of the applied compound, integration of metabolic and fungal profiling analyses revealed a more complex phyllobiome and a lower incidence of the pathogen in 'Moscato', which showed higher concentrations of stilbenoids than 'Nebbiolo'. These results unraveled distinct genotype-mediated defense mechanisms as main factors driving fungal community composition. Supported by Fondazione CRC, project 'SAFEGRAPE'"