CONICET | Buscador de Institutos y Recursos Humanos

Agriculture faces a growing global demand for food in combination with a reduction of fertile area due to climate changes and accumulation of pesticides and fertilizers worldwide. In this context, the development of new bioactive materials with emerging properties fits with the actual challenge of augmenting crop productivity with reduced environment impact. In agriculture, the use of toxic pesticides to control plant diseases is a common practice which causes hazards to the human health and environment [1].Chitosan (CS) is the second most abundant polysaccharide in natureafter cellulose, and it is a deacetylated derivative of chitin found mainlyin the exoskeletons of crustaceans [2].Despite the valuable contribution of new pesticides to control plant diseases, smart and sustainable options to develop a bioplaguicide as an alternative to agro-chemicals still remains as a challenge in phytopathology. In this sense, CS has been proved as an environmental friendly polymer for agricultural uses due to its wide spectrum biological activity including antimicrobial effect against many bacteria, fungi and yeasts, with a lower toxicity toward mammalian cells [3] and induce host defense responses in both monocotyledons and dicotyledons plants [4] Bentonite (Bent) is one of the most commonly used clays because of its easy industrial scaling, and low toxicity which allows its use in food and agriculture. Bent displays high cation exchange capacity, large surface area and porosity. Consequently, it has the possibility of lodging multiple organic cations between its sheets. The aim of our project is the production and characterization of sustainable agroimputs based in innovative nanoformulations. On one hand, we have developed CS microparticles (MP), basedon the polymer obtained from local shrimp waste, loading with different amounts of salicylic acid (SA) asthe anti-stress phytohormone and a master regulator of plant defense programs against biotic and biotic stresses.Both, CS-MP and CS-SA-MPtriggergrowth stimulation and plant defense responses withpositive traits to be used in agriculture. . On the other hand, in addition to CS, SA, and the multifunctional free aminoacidproline (Pro-L) as an antioxidant and osmoprotector against draught and salt were immobilized in Bent.; and Experimental Chitosan MPCS was synthesized from exoskeleton of Pleoticusmuelleriassociated to fish industry waste in Argentine. CS is obtained through typical three steps of demineralization, deproteinization anddeacetylation.MP Preparation. CS-based MPs were prepared by the gelation method with modifications using TPP as crosslinker. Firstly, 1 L of asolution of CS (0.1 or 0.2% w/v, pH 3.0), prepared in an aqueous solutionof 1% (v/v) acetic acid was kept under vigorous stirring. WhenCS was completely dissolved, SA was added in different ratios (1, 5, 10and 20% w/w with respect to CS)BentMaterials: Bent was provided by Minarmco SA (Argentina??)SA was provided by Sigma Aldrich (USA) and CS was obtained from DrogueriaSapporiti (Argentina?). Pro-L was provided from Biopack (pais). Modified nano clay Preparation: Bent−CS, Bent-SA and Bent-Pro nanoclays were obtained by cationic exchange by preparing a solution of the active agent and stirred it with a Bent dispersion in distilled water for 2 h. The anoclays obtained were then centrifuged, washed, and lyophilized.Characterization. Thermo gravimetric analysis (TGA): Analyses were performed using TA Auto-MTGA Q500 Hi-Res equipment in air atmosphere. X- Ray Difraction (XRD) patterns were obtained in a Analytical Expert Instrument equipment (K∞Cu=1.54 Å) from 2θ = 3 º to 60 º. Fourier transform infrared spectroscopy (FTIR): Nicolet FT-IR 7600 spectrometer was used with an ATR accessory. Bioassays: For the analysis of biochemical and physiological responses, composites were sprayed at different times and concentrations on tomato (Solanumlycopersicum cv. Platense) plantlets. Growth parameters and defense compounds were analysed along the plant life cycle. Results and Discussion CS based MPs were capable to entrap SA andprepared using TPP as crosslinker. MPs display sizes between 1.57 μm and 2.45 μm. Entrapment efficiencies from 59% to 98% and SA sustained release was measured over 24 h. CS MPswerenon-toxic in most of the doses applied in lettuce seedlings. MPs were able to modulate lettuce growth in addition to improve plant defence responses against environmental stress.In particular,SA loaded MPs activated defence protein in lettuce plants which were tested as a model of horticultural plant species.ForBent, powder XRD patterns showed that the distance between the planes of the crystal lattice of the modified clays (with SA, CS and Pro) was found to be higher than for unmodified Bent. The increased interlayer spacing of the clay after modification with each active principle (AP) indicates that at least some part of the AP were intercalated and housed in the clay strata. In the thermogramDTGA curves showed a peak of approximately 300 °C corresponding to the modified clay. However, it did not appear in those of the unmodified clay. This peak would indicate retarded degradation of intercalated active principle inside the clay. The absence of the peak corresponding to the hydroxyls (OH), centred at 3500 cm-1 and the carbonyl group (C=O) centred at 1710 cm-1 in the infrared spectra (FTIR) of the modified clay could be also related to the intercalation of the AP in the clay sheets. Bent-CS and Bent-SA clays sprayed on 10 days-old tomato seedlings elicited the accumulation of the PR2 which is a pathogenesis-related (PR) protein currently used as markers for innate immunity. Bent-SA application protected tomato plants against the infection with the phytopathogenicbacterium Pseudomonas syringepv. tomatoDC3000. In the case of Bent-CS showed antimicrobial actions against Pseudomonas syringep.v. tomato DC3000 and the necrotrophic fungus Fusariumsolani f. sp. eumartii. Similarly effects were also demonstrated for Bent-SA. Currently, experiments are in progress in order to evaluate the role of formulated Bent-APin the protection of plants against environmental stresses in the field. References 1.Mishra, S., Keswani, C., Abhilash, P., Fraceto, L. F., & Singh, H. B. (2017). Integrated approach of agri-nanotechnology: Challenges and future trends. Frontiers in Plant Science, 8: 471-485.2.Kanmani, P., Jeyaseelan, A., Kamaraj, M., Sureshbabu, P., &Sivashanmugam, K. (2017)Bioresource Technology, 242, 295?3032.3.Kong, M., Chen, X. G., Xing, K., & Park, H. J. (2010). Microbiology, 144(1), 51?63.4.El Hadrami, A., Adam, L. R., El Hadrami, I., &Daayf, F. (2010). Marine Drugs, 8, 968?

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