Elicitors of natural plant defense mechanisms: a new management strategy in the context of sustainable production. II. Interest for SDN in crop protection

Over the past decades, advances made in understanding the mechanisms involved in plants' induced resistance have stimulated the development of innovative projects that focus on the natural defense strategy of plants in a context that combines environmental preservation with the massive production of agricultural products. Today, an increasing number of formulations containing elicitors of natural defenses (or SDN, for stimulateur des defenses naturelles) as active ingredients are being marketed, and there is good reason to believe that more induced resistance-mediated molecules will be available in the near future. A SDN is a biological molecule capable of initiating the molecular, biochemical and cellular events that lead to the expression of plant resistance. As such, a SON is similar to a vaccine in that it is capable of stimulating a plant's immune system, thus turning a plant that was initially susceptible to a pathogen into a resistant one. If chitosan has been well known for years, other SDNs of various origins have recently been discovered, and some of them have been commercialized. Such is the case of lodus 40((R)), a beta-1,3-glucan polymer isolated form a brown alga, Messenger((R)), whose active ingredient is a bacterial peptide, and Stifenia((R)), which contains extracts from fenugreek, an African legume. Exploiting plants' induced resistance in biological agriculture or sustainable agriculture (alternation between biological control and chemical control) is a very promising strategy since it is essentially based on the stimulation of natural plant defense mechanisms. It is however obvious that more research is needed to demonstrate that this approach 1) does not present risks for consumers (allergies or other disorders); 2) does not affect yields; 3) is not too variable in terms of performance; and 4) is not too expensive compared with chemical control approaches.