BACKGROUND: Hydrogels are materials with great potential in agricultural applications. Biodegradable hydrogels are used as preparations, for example to increase the substratum water capacity, and improve soil structure or agrochemical-controlled release. This work aimed to develop biodegradable hydrogels based on chitosan, gelatin and polyvinyl alcohol (PVA) for releasing inulin isolated from Dahlia tubers to induce protection in chili plants against Phytophthora capsici. The hydrogels were characterized by water absorption capacity, Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and stereomicroscopy microscopy, and degradation capacity using the soil burial test with sterile and inoculated soil. RESULTS: This work demonstrated the ability of a fabrication process in the preparation of gelatin-chitosan-PVA hydrogelsfor potential agricultural applications. The hydrogels showed a dense, tridimensional, interconnected and reticulated structure that was more evident in the hydrogel loaded with inulin. The hydrogels showed a water absorption capacity of ≤12 times its mass. FTIR and light microscopy demonstrated that the hydrogels were biodegradable. The percentage of degradation of hydrogels in inoculated soil was higher than in sterile soil using the soil burial test. Hydrogel loaded with inulin was found to be capable of inducing resistance in chili plants against Phytophthora capsici. CONCLUSION:The hydrogels prepared for the described methodology have great potential for use in the agricultural sector as a reservoir for agrochemicals and inductors in plant resistance treatments. Furthermore, the hydrogels were proven to be biodegradable, offering a promising tool in crop protection. Surface morphology of hydrogelsThe hydrogels have a polyhedral irregular shape. Figure 5(a) shows that the surface morphologies of the hydrogels revealed the formation of a reticulate heterogeneous network. When the hydrogel was loaded with inulin and freeze-dried again, inulin aggregates between the macro channels of the structure [Fig. 5(b)]. Biodegradation test of the hydrogelThe degradation of the hydrogels (H and HI), that were buried in the sterile and inoculated soil were monitored after 7, 14, J Chem Technol Biotechnol 2019; 94: 3495-3504

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Chitosan is a natural polymer, and its biological properties depend on factors such as the degree of deacetylation and polymerization, viscosity, molecular mass, and dissociation constant. Chitosan has multiple advantages: it is biodegradable, biocompatible, safe, inexpensive, and non-toxic. Due to these characteristics, it has a wide range of applications. In agriculture, one of the most promising properties of chitosan is as an elicitor in plant defense against pathogenic microorganisms. In this work, four kinds of chitosan (practical grade, low molecular weight, medium molecular weight, and high-density commercial food grade) were used in concentrations of 0.01 and 0.05% to evaluate its protective effect against coffee rust. The best treatment was chosen to evaluate the defense response in coffee plants. The results showed a protective effect using practical-grade and commercial food-grade chitosan. In addition, the activity of enzymes with β-1,3 glucanase and peroxidase was induced, and an increase in the amount of phenolic compounds was observed in plants treated with high-molecular-weight chitosan at 0.05%; therefore, chitosan can be considered an effective molecule for controlling coffee rust.