Ph. D. Sebastien BRUISSON

Potentiation of defense responses following mycorrhization of Grapevine and effects on stilbene production.

Defended in April 2015.

Supervisor: Pr. Bernard Walter

Co-supervisors: Pascale Maillot and Laurence Deglène-Benbrahim.

Chemical control is widely used to limit the impact of the main vine diseases, however the most efficient phytosanitary products are toxic for the environment and the consumer.

The work presented in this thesis explores the use of AMF (Arbuscular Mycorrhizal Fungi) to obtain plants that are less susceptible to diseases. These AMF naturally have the ability to associate with the roots of many plant species, including grapevines, to form a symbiosis, one of the effects of which is the establishment of an induced resistance called MIR (Mycorrhiza-Induced Resistance). This resistance is manifested by the stimulation and/or potentiation of defense pathways. Potentiation is characterized by a faster and stronger recruitment of defenses when the plant is confronted with a pathogen.

Analyses by qRT-PCR show that the presence of AMF in the plant potentiates the expression of several defense genes in leaves and roots (Pinot noir grafted on 41B), as revealed after foliar treatment with Bion®, a chemical elicitor analog of salicylic acid, or infection by the pathogens P. viticola and B. cinerea. In addition, HPLC assays show higher concentrations of stilbene compounds (pikeid, resveratrol, viniferins and pterostilbene) in leaves of mycorrhizal plants following infection by these two pathogens.