BBI project. Impact of P. oligandrum on grapevine trunk studies

Grapevine trunk diseases have become a major concern in viticulture. Since the ban in 2001 of sodium arsenate (the only approved pesticide), the use of alternative methods, such as biocontrol, has become a major issue. Among the promising microorganisms, the oomycete Pythium oligandrum is known to improve the plants health by increasing their natural defenses and reducing diseases to up than 40%. The BIOBESTicide project (BIO-Based pESTicides production for sustainable agriculture management plan), funded by the European Commission, aims to industrialize the production of a biopesticide solution to fight grapevine trunk diseases. Efficiency evaluation of the product formulated from P. oligandrum will be carried out at different scales, from the nursery to vineyards, and the environmental impact of this solution will be assessed in order to ensure its safety. Thus, an experiment in semi-controlled conditions was carried out in a greenhouse with the objective of assessing the impact of the P. oligandrum biopesticide on microbial communities by a high-throughput sequencing approach. Overall, 240 vines were treated with two P. oligandrum formulations and were inoculated with two fungi involved in wood diseases: Neofusicoccum parvum (involved in Botryosphaeria Dieback) and Phaeomoniella chlamydospora (involved in ESCA). A three-month follow-up was carried out with samples from different compartment plants (leaves, wood and rhizosphere environment) to allow the evaluation of potential changes on microbial communities, whether as part of grapevine trunk disease or after P. oligandrum action. The results obtained revealed that the microbial communities were driven by plant part, regardless the treatment. Moreover, the addition of P. oligandrum had no effect on the rhizosphere microbial communities, which may suggest that the biopesticide is environmentally safe.