Study on the chitinase-induced efficiency against anthracnose on soybean plant by oligochitosan-Zn2+ complexes

Anthracnose caused by Colletotrichum truncatum (C. truncatum) fungus, a seriously 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 on soybean plants of various oligochitosan-Zn2+ (OC–Zn2+) complexes prepared from gamma radiation-degraded oligochitosans 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 at 50 ppm and inoculated with a disease by a fungal spore suspension spray of C. truncatum to assess the chitinase-elicited effect. The chitinase activity (CA) which described in milliunits per gram (mU/g) of fresh leaves in soybean was determined by the optical density measurement method 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 with Mw of 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 on a large scale. Thus, the complexes have been promising to be potentially applied in sustainable agriculture production.