A total of 61 wheat genotypes were screened for powdery mildew disease under natural infection during two
seasons 2012/2013 and 2013/2014 in El Quantra Shark. Genotypes were sown in randomized complete block design in
three replicates. The disease severity for all genotypes was measured to estimate the reaction of each genotype to infect
with powdery mildew. The first scoring was done when the majority of genotypes were in the late booting stage. The
second experiment to examine the effect of nitrogen fertilization and water deficiency on severity of powdery mildew
disease and loss of yield. The experiment was carried out at the experimental Farm of Agronomy Department Fac.,
Agric., Suez Canal Univ., and Ismailia on Sids 12 wheat cultivar. Irrigation allocated at the main plots and the nitrogen
fertilization allocated in sub main plots. Twelve lines showed moderately resistant reaction while thirty eight lines
showed moderately susceptible and eleven lines recorded susceptible reaction to infect with Blumeria graminis tritici.
The genotypes 2, 10, 11, Sakha 94, Sids 12, 66, 82, 89, 91 and 102 recorded the higher yields. Result indicates that
increasing nitrogen dose from low (50 kg/fad. N) up to high N (100 kg/fad. N) had a clear effect on powdery mildew
infection.