Deciphering microbial interactions protecting grapevine against downy mildew: Integrating field studies and synthetic community approaches
Résumé
Grapevine hosts numerous microorganisms that impact its health and growth. Among the key pathogens are Plasmopara viticola (downy mildew) and Erysiphe necator (powdery mildew). When these pathogens colonize grapevine leaves, they encounter the resident microbiome, which can act as a barrier to their growth through various ecological interactions. Additional interactions may occur in the soil and litter but these have been largely overlooked. A current challenge is to identify microbiome members that naturally regulate mildews and find management practices that support these natural antagonists. To address this, we analyzed leaf and soil microbiomes in vineyard plots with long-term epidemiological records. We compared microbial community compositions between plots with contrasting disease susceptibilities and between symptomatic and asymptomatic tissues. Using differential abundance analyses, Random Forest algorithms, and network learning methods, we identified potential antagonists or facilitators. Microbial taxa of interest for downy mildew were found in the topsoil, which serves as both a microbial reservoir and the overwintering site for pathogen oospores, and in the phyllosphere, where pathogen zoospores enter leaves. The leaf endosphere contained very few taxa of interest. The diversity of microbial communities was not consistently related to disease susceptibility, suggesting that susceptibility is more related to the abundance of specific microbial taxa. Several taxa were integrated into Synthetic Microbial Communities (SynComs) and tested against downy mildew in vitro and in the field, aiming to develop microbial biocontrol of grapevine diseases and move towards pesticide-free viticulture.
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