Inducing resistance against powdery mildew caused by Sphaerotheca fuliginea in cucumber (cv. Beta Alfa) was investigated under filed conditions as fungicides alternatives. Biotic inducers (Bacillus subtilis) were sprayed onto the upper two true cucumber leaves. And water was used as negative control. Further, specific activities of defense-related enzymes (peroxidase, polyphenol-oxidase,catalses) and total phenols were spectrophotometrically measured in cucumber leaves and after inoculation with fungal spores. Results showed that, biotic tested inducers reduced the disease severity on the treated leaves, increased (plant length, root length, and plant dry weight) and increased the activities of defense-related enzymes, low doses of gamma radiation increased the vegetative growth specially doses at 15 and 20 Gray (Gy).