Elicitors Of Natural Plant Defense Mechanisms: A New Management Strategy In The Context Of Sustainable Production. I. Principles Of Induced Resistance

For a long time, agriculture across the world was dependent on pesticides. Today, it is influenced by a movement that favours practices that are more sustainable and environmentally safe. To meet these new demands, producers wishing to exploit natural resources and make them profitable must turn to new agronomic practices that combine culture performance and protection at a low environmental cost. In this context, the development of biological molecules able to stimulate natural defence mechanisms in plants (or SDN, for "stimulateurs des defenses naturelles des plantes") is a strategy that attracts much attention. A SDN molecule is an elicitor capable of initiating a series of biochemical events leading to the expression of disease resistance in plants. Signal perception by ultra-specific membrane receptors and its transduction by diverse signalling pathways lead to the synthesis and synchronized accumulation of defence molecules; some of these molecules play a structural role while others have a direct antimicrobial function. Structural barriers contribute to delaying pathogen ingress in plant tissues and prevent the diffusion of deleterious substances such as cell wall hydrolytic enzymes or toxins. Biochemical mechanisms include, among others, the synthesis of stress proteins and protease inhibitors as well as the production of phytoalexins, which are secondary metabolites with a strong antimicrobial potential. The remarkable advances made over the last few years as regards our understanding of the mechanisms involved in induced resistance in plants now translate into the marketing of an increasing number of SDN molecules able to stimulate a plant's "immune system" by mimicking the effect of pathogens.