Concerning axis 2, in the current agro-ecological context, which aims to reduce the use of conventional chemical inputs in agriculture, the development of alternative methods of crop protection is an expectation of the agricultural world, which is materialized by reduction plan of chemicals in agriculture (Ecophyto 1 and 2). In order to help meet this demand, we are looking for biomolecules that have elicitric properties, or biocides that allow a direct (biocidal) or indirect protection (stimulation of the defenses of the plant) against pathogens. In addition to the screening of candidate biomolecules, the work focuses on the efficacy and mode of action of these molecules using phenotypic, cytological, biochemical and molecular markers. The molecular approach requires the implementation of a quantitative PCR (qPCR). This device makes it possible to highlight the genes expressed during the defense reactions of the plants and consequently the metabolic pathways used.