The aim of the project is to study the response mechanisms induced by biostimulants on tomato plants under controlled conditions and production conditions. In particular, the objective is to determine the direct contribution of biostimulants on plants and their indirect contribution, through the variations in rhizosphere and phyllosphere microbiota.We planned a three-stage approach: Product –Soil – Species. The product approach aims at screening the most effective products for biostimulation in tomato under water stress. Biosolutions of various natures are tested: algae extract, vegetal extract, mineral. The soil approach is designed to assess whether selected biostimulants at the end of the screening influence the microbiota of various types of soil (natural, artificial). The species approach will enable us to conclude if the biostimulants effects can be generalized on different crops.In 2024, we set up an experiment on tomato crop under water stress conditions (n=500). Sevenbiostimulants are tested with two foliar applications, from the 4-6 leaf stage and at 7 days of interval. The stress is applied two weeks after the first treatment. We are carrying out observations and phenotypic measurements at ten time points until fruit production. We also take samples of leaves and roots for metabolomic analysis. This trial is conducted in semi-controlled condition, in a greenhouse. Then, at the end of 2024, the study of the biostimulant effects on plants and plant microbiota will be performed in controlled condition (in vitro and in a growth chamber). We are considering metabolomic investigations combined with metagenomic to assess the influence of selected biostimulants on the phyllosphere and rhizosphere microbiota communities and their functions.Thanks to this project we hope to gain insights into the mechanisms by which plants develop resilience to abiotic stress in response to biostimulant applications directly and on the indirect contribution via the microbiota.Read less <