Preparation of radiolysis-degraded oligochitosan, oligochitosan-Zn²⁺ complex and their induced effect against Anthracnose on soybean plants

Anthracnose is the severely devastating disease in soybean cultivation. Employing chemical fungicides have been limited in modern agriculture. Currently, the oligochitosan (OC) and OC-Zn²⁺ complex have been evaluated as efficient fungicides. However, finding a proper method to produce them is still being actively encouraged. This work presents a preparation of 4% OC solution (Mw∼5000 g/mol, the chemical structure unchanged in comparison with the chitosan) by gamma-ray irradiation combined with a small amount of H₂O₂. The OC-Zn²⁺ complex were prepared from OC and Zn²⁺ ion with a molar ratio of 1/0.5 by stirring at ambient condition. The importance characterization of OC-Zn²⁺ complex were determined by the GPC, UV-Vis, XRD, FT-IR techniques and that was evaluated the effectiveness of anthracnose resistance Soybean plants grown in a greenhouse. After the third spraying, a spore suspension of C. truncatum was introduced. The obtained results indicated that the OC-Zn²⁺ complex exhibited a significantly stronger disease resistance than that of OC. The disease incidence was of 52.2 % and 33.3 % (compared to 92 % of the control); disease severity was of 35.7 % and 13.8 % (79.9 % in the control) for OC and OC-Zn²⁺, respectively. Thus, the OC-Zn²⁺ complex has the potential for large-scale production and agricultural application. (author)