Bioactive carbohydrate from potato peels: A sweet inducer that mediate resistance against powdery mildew disease of cucumber through phytohormonal alterations

Large volumes of nutritive wastes are generated by food industries, which can be used in the production of bioactive compounds of commercial values. The waste generated by potato chips industries contains high quantities of insoluble starch, high concentrations of total suspended solids and chemical oxygen demand, or environmental issues. In this study, the starch extracted from the potato peels was subjected to bioconversion of isomaltose-oligosaccharide by enzymatic method and further eluted isomatlose by liquid chromatography-mass spectrometry. The structural elucidation of isomaltose was confirmed by 1H NMR and 13C NMR spectroscopy. The purified isomaltose displayed excellent in vitro antifungal action against Erysiphe cichoracearum and Fusarium oxysporum at concentrations 1.0 and 2.5 mg/ml, respectively. Notably, cucumber-seeds primed with isomaltose (2.5 and 5.0 mg/mL) concentrations recorded a significant improvement of germination (91.5 and 89 %) and vigor (2210.93 and 2015.7) over the untreated control. Subsequently, the isomaltose-primed cucumber plants challenged with powdery mildew pathogen showed enhanced protection of 63% in comparison with pathogen alone-induced plants. This enhanced growth parameters and induced resistance in cucumber may be fairly contributed by the upregulation of phytohormone levels in primed plants observed in this study. Taken together, this study is unique in the use of bioactive isomaltose from potato peels, which could enable us to minimize the agro-industrial wastes and most importantly could help to develop new formulations for sustainable crop protection strategies.