Characterizations of Oligochitosan-Degraded Irradiation and Chitinase-Induced Efficiency by Oligochitosan-Zn²⁺ Complexes on Soybean Plant

Colletotrichum truncatum (C. truncatum) fungus, a seriously one-damaged in many soybean growing areas, has almost no effective control strategy. Recently, biostimulants for disease prevention of plants have been considered a feasible solution. In this study, the chitinase-induced effect, a marker of pathogen-related proteins, on soybean of various oligochitosan-Zn²⁺ (OC-Zn²⁺) complexes prepared from gamma radiation-degraded OCs with the different molecular weights (Mw) of 2.5, 5.1, and 7.8 kDa was investigated in the first time. The potted soybean plants in a greenhouse were treated with a foliar spray of OC-Zn²⁺ solutions and inoculated with a disease by a fungal spore suspension spray of C. truncatum to assess the chitinase-elicited effect. The chitinase activity (CA) of fresh soybean leaves was determined by the optical density measurement based on the reducing sugar reaction. The obtained results indicated that the OC-Zn²⁺ complex exhibited a synergistic effect of OC and Zn²⁺. The OC5.1-Zn²⁺ complex prepared from the OC 5.1 kDa showed a high chitinase-induced effect with the CA ~12 mU/g. The OC-Zn²⁺ complexes with effective chitinase inductivity could be feasibly produced into mass production. Thus, the complexes have been promising to be potentially applied in sustainable agriculture. (author)