Deciphering the modes of action of bacterial biocontrol agents, candidates for control of Sclerotinia sclerotiorum on oilseed rape

Abstract: Oilseed rape (Brassica napus), one of the main cultivated oleaginous crops
worldwide is susceptible to white mold caused by the fungal pathogen Sclerotinia sclerotiorum. Control of this necrotrophic and polyphagous fungal pathogen relies mainly on chemicals. Therefore, the development of biocontrol agents appears as a promising option to contribute to a more sustainable production of rapeseed. Previous work by our team has identified two bacteria with particularly promising activity against S. sclerotiorum under controlled conditions and in the field. A biocontrol solution based on these bacteria is currently being developed in close collaboration with a company. In order to further develop this solution, we are undertaken the study of the mode(s) of action of these bacteria. Better knowledge of the biocontrol mechanisms of strains and of the abiotic conditions favourable to the expression of the modes of action are required to develop biocontrol agents that are more effective. As part of my PhD, my objectives are to assess the ability of the both candidate bacteria to synthesize metabolites of interest, to identify the metabolites produced, to evaluate the conditions for their synthesis, and to assess the direct effect of these metabolites on the fungus and on the defense mechanisms of the plant.