Fungi as biocontrol agents: screening strategy towards various plant pathogens – promising results on potato plants challenged by Phytophthora infestans

Potato plants are facing numerous pathogens. Among these is Phytophthora infestans, the causal agent of late blight. Currently, chemical treatments are the most recommended strategies for the control of this disease, despite their detrimental impacts on environment and human health. The development of alternative strategies is thus becoming essential for reducing/controlling pesticides applications. In that context, the use of fungi and fungal bio-effectors represents a promising strategy to control, at least partially, below and above-ground pathogens, and the screening of collections opens the perspective of discovering new environmental-friendly actives molecules. The main objective of our research was to develop an efficient screening method to identify efficient fungal strains for the biocontrol of P. infestans and alternatively of other fungal diseases. One hundred fifty fungal strains were first selected from the literature for their potential as biocontrol agent. These strains were provided by the Mycothèque of the Université catholique de Louvain (BCCM/MUCL), one of the world largest collection of fungi of agro-food and environmental interest. A 96-well microplate in vitro test was used to screen crude extracts of the fungal collection. Sixty-nine organisms (i.e. crude extracts) displayed a strong inhibitory on the growth of P. infestans. Their potential activity was then evaluated in vitro on potato plantlets grown in microboxes. Seventeen strains showed a strong activity against P. infestans. These strains mostly belong to Aspergillus, Chaetomium, Fusarium, Hyphomyces, Penicillium and Trichoderma species. Further isolation, purification and characterization of the active molecules are on-going. This screening strategy allows the fast track identification of fungi as well as fungal bio-effectors effective against P. infestans and will be extended to other major root and shoot pathogens in the SMARTBIOCONTROL project