CHITOSAN AND ITS HYDROLYSATE AT TOBACCO-Phytophthora parasitica INTERACTION
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Instituto Nacional de Ciencias Agrícolas
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Chitosan is the non-acetylated derivative from chitin, a polymer of N-acetyl-glucosamine that is extracted from crustacean exoskeleton. Both polymers as well as their oligomers protect several species of plants against fungal diseases by means of the induction of histological and biochemical defensive mechanisms that stop pathogen advance in the plant. In our work a chitosan preparation was carried out by means of basic desacetylation of chitin of pharmaceutical quality. Afterwards, chitosan was exhaustively hydrolyzed with a commercial enzymatic preparation (celluclast) to obtain small-sized oligomers. Chitosan polymer and its hydrolysate were studied regarding their potentialities to induce systemic resistance in tobacco plants by means of assays under controlled conditions where the capacity of both elicitors was determined for the induction of resistance markers (chitinase, glucanase and PAL activities) and in the hydrolysate case, its capacity to induce tobacco plantlet protection against the invasion of pathogen Phytophthora parasitica var. nicotianae was also tested. Results demonstrated an induction of chitinase and glucanase activities by chitosan at the concentrations of 50 and 500 mg.L-1, much higher in the case of the topmost concentration of the elicitor. Tobacco plantlet protection against Ppn was also observed when plants were treated through the roots with the enzymatic hydrolysate at the concentrations between 5 and 500 mg.L-1 with an induction of differentiated PAL and â 1-3 glucanase response during plant exposition to the pathogen.
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