Abstract: The application of oligosaccharides has been shown to have effects in regulating crop growth, delaying senescence and improving resistance. In order to investigate the mechanism and reveal the effects of oligosaccharides on metabolites in the rhizosphere soil surrounding the plant, a cucumber greenhouse experiment was conducted in this study. The mixed-oligosaccharide (KP) was selected as the preparation treatments, while tap water control (CK) were compared as controls. During the full flowering, full fruiting and seedling stages, the rhizosphere soil samples around cucumbers were collected and analyzed to identify the differences in metabolites among different treatment groups using gas chromatography-mass spectrometry (GC-MS) method. The results showed that the cucumber treated with oligosaccharides (KP) during the full flowering period showed significant differences in bulk soil metabolites when compared with the water control group (CK). Meanwhile, nonanoic acid was the most up regulated substance, with a difference multiple of 2.795. However, the amount of heterocyclic compounds and sugars decreased. The heterocyclic compounds showed the most significant reduction in substance content, by a difference multiple of 0.002. Based on the KEGG metabolic pathway analysis, there was a significant difference in metabolic pathways between KP and CK treatment, with a difference ratio of 83.33%. Based on differential metabolite enrichment analysis, it was believed that the mixed-oligosaccharides could increase the content of nonanoic acid in the rhizosphere soil by up regulating the expression of the lipoic acid pathway, while the decrease in heterocyclic compounds and carbohydrate content might be related to the down regulation of bacterial chemotaxis metabolism, fructose and mannose metabolism pathways during the full flowering stage.

Key words: Mixed-oligosaccharide, Cucumber, Full flowering stage, Rhizosphere soil, Metabolites