Chitosans as bioactive macromolecules to protect economically relevant crops from their main pathogens

ABSTRACT Studies were carried out as part of the Agriculture Biotechnology program, to prepare and characterize chemically and biologically different chitosans obtained from Cuban lobster chitin. Chitosan polymers were subjected to acid and enzymatic hydrolysis by using low-cost commercial enzymatic preparations, and the resulting oligosaccharide mixtures were further characterized. Their potential antimicrobial activities were also evaluated versus fungi and oomycetes, also testing their ability to induce defensive and protective responses in tobacco and rice plants against two economically relevant pests, Phytophthora nicotianae and Pyricularia grisea, respectively. With the aid of international collaboration, different oligochitosans mixtures were compared for activating defensive responses in suspension cultures of Arabidopsis thaliana cells. These results bring knowledge on the physical-chemical properties of the chitosans obtained, such as molar mass and acetylation grade, and their influence on activating defensive responses, the inhibition of growth in pathogens and the induction of resistance in tobacco and rice plants. Some of these chitosan derivatives were selected as possible active components to protect both type of cultivars, being applied at field-scale to evaluate their effects for the main natural pathogens and bringing very promising results. This research allowed us to establish a methodology for preparing oligochitosans, and results shown inhere were part of BSc, MSc and PhD theses, and were also published in more than 20 scientific papers and presented in more than 40 scientific conferences