Abstract: The potted test indicated that the glucohexaose can induce the disease resistance of cucumber to cucumber downy mildew and protective effect was 65.40% after glucohexaose inducing three times continuously. The content of salicylic acid in different time was assayed through reverse phase HPLC, which demonstrate that there is a peak in one day after glucohexaose inducing the young cucumber three times continuously, and SA content is alwaysmuch higher than control in eight days. When glucohexaose treats only one time,SA content of induced leaf ( the first euphylis) increase remarkably, and there is a peak in six hours, but noninduced leaf ( the second euphylis) having a peak in twelve hours after induce treatment.

Key words: Glucohexaose, Cucumber, Downy mildew, Induced resistance, Salicylic acid