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Eliciting, antimicrobial and film-forming properties of chitosan applied on fresh fruit and vegetables

Gianfranco Romanazzi: Marche Polytechnic University

<div><span lang="EN-US" style="font-family:'Calibri';">Chitosan is a natural biopolymer obtained from crab shells known for its biocompatibility, biodegradability and bioactivity. In human medicine, it is used as stabilizer for active ingredients in tablets, and it is popular in slimming diets. Due to this low toxicity, it is the first compound in the list of basic substances (Reg. EU 2014/563) approved in EU for plant protection, in both organic agriculture and IPM. When applied to plants, chitosan shows a triple activity: i) elicitation of host defenses, ii) antimicrobial activity, and iii) ability to form a film on the treated surface. The eliciting activity of chitosan was studied since the 1990’, starting monitoring the activity of enzymes linked to defense mechanisms (chitinase, β-1,3 glucanase, phenylalanine ammonia-lyase, etc.) in different fruits (i.e. strawberries and other berries, citrus, table grapes), followed by investigations with qRT-PCR and in the last years with RNA-Seq. The antimicrobial activity of chitosan against a wide range of plant pathogens is confirmed by thousands of in vitro and in vivo studies. Once applied on a plant surface by dipping or spraying, chitosan is able to form an edible coating, whose properties (i.e. thickness, gas and water permeability) depends on the acid in which the biopolymer is dissolved. Several commercial chitosan formulations are available to be used as a biopesticides, and their effectiveness arise from the combination of the three involved mechanisms of action.</span></div>