Study of PR Gene ExpressionPattern related to in Induced Resistance to Powdery Mildew in Susceptible Wheat Genotype after Treating with Salicylic Acid

Bread wheat is one of the most important food crops which has main position in nutrition of the world''s population. The production of this crop were always been faced to a variety of challenges. Powdery mildew¡ caused by the biotrophic pathogen Blumeria graminis f.sp tritici (Bgt)¡ known as a destructive disease of wheat worldwide. There are several methods to control the disease¡ but use of inducers as of SA¡ able to induce a systemic resistance in plants are very important. In order to examination the ability of SA for inducing resistance in wheat against Bgt fungus¡ Flat was selected as susceptible cultivar and treated with SA and then exposed to Bgt fungi together with control plants. Then examine the expression rate of PR1¡ PR2¡ PR3 and PR5 genes using Real Time PCR technique in response to Bgt was carried out at 5 time courses and in 3 independent replicates. Results indicated that in both groups of treated and control plants¡ levels of gene expression were increased after infection for all genes. Maximum expression level of genes were observed at 24 hours after infection. This process was observed slowly in control plants but caused early and faster induction of plant defense genes in treated plants early hours after infection rather than control plant. At 48 hours after inoculation¡ transcript levels of induced genes started to dampen in both groups of experimental plants¡ indicating effective suppression of defense associated genes upon haustorium development. Overall¡ results indicated that SA inducer beacause of able to induce resistance in susceptible cultivar through overexpression of resistance genes and reducing number of colonies grown on Bgt fungus per unit area can one of the candidate of induced resistance in susceptible cultivar.