Natural elicitors of plant defense response in strawberry

Natural substances such as elicitors of plant defense response, has become a promising option for effective management of plant diseases and are a prerequisite for sustainable and ecological agriculture. Recognition of diverse elicitors, effectors and modulators by specific and nonspecific plant receptors activates signalling cascades eventually leading to gene expression and defense responses. Elicited plants or primed plants display either faster, stronger, or both activation of the various cellular defense responses that are induced following attack by either pathogens or insects or in response to abiotic stress. The aim of this work has been to develop new elicitor compounds from natural vegetal substrates, and predict its effectiveness in the field by using robust molecular techniques and appropriate biomarkers of plant defense. Thus, Fragaria x ananassa Duch. cv. Chandler cell suspension cultures, and real-time, quantitative PCR analysis (RTqPCR) were utilized to test the elicitor capability of new natural elicitors. This experimental approach was applied to analyze the pattern of gene expression of specific strawberry genes already known to be good markers of SA- and JA-dependent signalling pathways, which were used as defense induced biomarkers in plants. In addition, determination of total phenols and antioxidant activity, and HPLC-DAD-MS analysis of polyphenolic compounds was performed in these cell suspension samples. Susceptibility to C. acutatum of strawberry plants treated with the new elicitor was performed in greenhouse under controlled conditions. In collaboration with AGROMETODOS, S.A., we have produced new natural compounds that can act as elicitors. We have compared the elicitor activity of a new compound (EH) with the commercial product BROTOMAX (R). The new product EH and BROTOMAX (R) activate plant defense related genes in cell suspension cultures. Also, both products induce polyphenol production in this assay. The new product EH and BROTOMAX (R) increased the strawberry (Fragaria x ananassa Duch. cv. Camarosa) and olive (Olea europaea L. cv. Picual) resistance against Colletotrichum acutatum and Fusicladium oleaginum plant infections, respectively. We can conclude that new natural bioelicitors can be produced by low-cost procedures based on fermentation of natural substrates derived from plants. The use of suitable, sensitive, appropriate and robust molecular biomarkers also provide an excellent molecular tool to predict the effectiveness in the field of natural compounds with potential eliciting ability, which may be conveniently exploited as ecological bioinducers of plant defense response in strawberry and in many other important crops.