Abstract—This study aimed to evaluate the effect of some different biotic and abiotic inducers i.e., potassium silicate, humic acid,
propolis extract, and died spores (DS) of Pseudoperonospora cubensis in addition to amistar fungicide in controlling cucumber downy mildew
disease and induction the systemic acquired resistance of treated plants in protected houses. Spraying cucumber plants with all tested inducers
reduced disease severity of downy mildew and increased the fruit weight/plant. Amistar fungicide followed by potassium silicate and DSI were the
best effective treatments without significant differences between them in reducing disease severity and increasing fruit weight/plant respectively. All
treatments increased phenols and flavonoids, content in treated cucumber plants at 2, 5 and 8 days post inoculation with the downy mildew
pathogen. Also, spraying cucumber plants with the tested inducers increased the activities of peroxidase (PO), polyphenoloxidase (PPO),
phenylalanine ammonia lyase (PAL), chitinase and β-1,3- glucanase enzymes post inoculation the plants with downy mildew pathogen. In general,
the died spores of DS1 followed by DS3 and potassium silicate were the most effective treatments in increasing activities of PO, PPO and PAL
enzymes. Meanwhile, the died spores of DS3, DS1 and DS2 followed by potassium silicate were the superior in increasing the activities of
chitinase and β-1,3- glucanase enzymes in leaves of treated cucumber plants in protected houses.