Powdery mildew disease elicited by Blumeria graminis f. sp. tritici( Bgt) occurs worldwide in wheat crops and can reduce grain yield from 5 to 45% depending on the severity of invasion. Although, barley is resistant to Bgt, there is a little information about the non-host resistance ( NHR) mechanisms. In barley, expression of a gene of the PR-1 family, PR-1b, is frequently as a reliable marker during challenge with B. graminis and other pathogens. When the plant gene MLO was expressed, the powdery mildew species could penetrate within the epidermal cells of the host plant. Therefore, we evaluated their effects on non- host resistance response against Bgt using qpcr technique, along with the different time courses from 0- 48 hour after inoculation(HAI) respectively 0, 24, 36 and 48 HAI on seven- old days barley seedlings leaves with Bgt. Results showed that the maximum genes expression of PR-1recorded after 24 HAI. Simultaneously, suppression of MLO gene significantly occurred in this time. This results showed that stability of barley resistance to Bgt conferred by expression of the mentioned gene in salycilic acid pathway that could prevent from pathogen ,s progress. PR-1 accumulated locally and systemically, suggesting an involvement in systemic acquired resistance in this type of NHR. Hypersensitive response( HR) detected with DAB staining method in the non-host barley leaves- Bgt interactions in 48 HAI. Result indicated Reactive Oxygen Species (ROS) key role in regulation of this type ( ɪɪ) non-host resistance. Perhaps accumulation of ROS associated with creating unfavorable conditions suppressed MLO gene expression.