Use of Elicitors and Beneficial Bacteria to Induce and Prime the Stilbene Phytoalexin Response: Applications to Grapevine Disease Resistance

Phytoalexins are naturally occurring molecules with antimicrobial activity deriving from the secondary metabolism of plants; they are synthesized in response to physical agents or stresses and phytopathogenic agents (fungi, bacteria and viruses), as well as numerous chemical compounds and biological control agents. Among these, grapevine phytoalexins, which belong to the chemical group of stilbenes, exhibit biocidal activity against a large number and variety of plant pathogens. It is important to investigate whether induction of stilbene phytoalexin production can serve to protect this plant against its pathogens. Quite a few chemical compounds, derivatives of phytohormones bio-elicitors as well as biocontrol agents, have been used to induce the synthesis of stilbene phytoalexins with the aim of conferring protection to grapevine against its main diseases (gray mold, downy mildew, powdery mildew and esca). This article reviews the experiments that have been carried out in this direction during the last 30 years and shows that the observed protective effects towards pathogens are generally linked to induction and priming of the grapevine phytoalexin response, confirming the interest in using, in a more general way, stimulation of the production of phytoalexins in plants as a basis for crop protection.