Derivatives of chitosan-ethyl formate polymers (Chs-EF) show promise as biologically relevant materials. The novelty of this study lies in the innovative use of Chs-EF doped with zinc oxide nanoparticles and beta-cyclodextrin, which significantly enhances the polymers' protective activities against Alternaria early blight disease in Vicia faba by improving both disease resistance and plant health. After doping Chs-EF with zinc oxide nanoparticles (ZnONPs) and inserting it into the beta-cyclodextrin (CD), two products emerged: Chs-EF/ZnONPs and Chs-EF/CD. Using βCD and ZnONPs to modify the Chs-EF polymer improves the optical properties of the generated polymers. Also, the energy gab values of the modified polymers (Chs-EF/ZnONPs and Chs-EF/βCD) were 3.3 and 3.7 eV, respectively, while energy gab value of the Chs-EF polymer was 3.9 eV. In this study, the effects of ZnONPs, chitosan, β-CD, and Chs-EF/ZnONPs on Alternaria solani early blight disease in Vicia faba plants were investigated. The treatments were evaluated based on disease symptoms and a disease index (DI) to assess their ability to protect against Alternaria early blight disease blight. The results show that the modified polymer with ZnONPs and beta-cyclodextrin (β-CD) and the modified polymer with ZnONPs (Chs-EF/ZnO NPs) provided the best protection, with DI values of 25 % and 12.5 %, respectively. Furthermore, it was discovered that the levels of carotenoids, chlorophyll a, and chlorophyll b in the infected plants had dropped by 52.6 %, 69.2 %, and 36.1 %, respectively. Chs-EF/ZnONPs were the most effective treatment, showing significant increases in the contents of chlorophyll a and b in infected plants by 120.8 % and 225.4 %, respectively. The study revealed that Chs-EF/ZnONPs exhibited a 131 % increase in the total phenolic content of plants, peroxidase (POD) activity (110.6 %), and a 347 % increase in polyphenol oxidase (PPO) activity, respectively, compared to healthy plants. Malondialdhyde (MDA) decreased by 50.7 %, 49.7 %, 43.4 %, 36.6 %, 31.7 %, and 7.5 % in response to Chs-EF/ZnONPs, Chs-EF/β-CD, Chs-EF, ZnONPs, Chitosan, and β-CD, respectively. Also, application of Chs-EF/ZnONPs, Chs-EF/β-CD, Chs-EF, ZnONPs, Chitosan, and β-CD reduced the production of H2O2 by 77.5 %, 62.8 %, 62.5 %, 39.6 %, 22 %, and 15.1 %, respectively, compared to infected controls. We recommend considering these substances as promising candidates for agricultural use, as they may effectively serve as control agents against early blight caused by Alternaria solani.
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