Changes in PR2 and PAL Patterns in Barley Challenged with Leaf Stripe (Pyrenophora graminea) and Powdery Mildew (Blumeria graminis) Diseases

The seed-borne (Pyrenophora graminea; Pg) and foliar (Blumeria graminis; Bg) are two economically important fungal pathogens of barley worldwide. Barley plant resistance genes, as the pathogenesis related proteins play an important role in defense mechanisms. This study aimed to monitor the expression of PR2 and PAL pathogenesis related genes during compatible/incompatible barley interaction with Pg and Bg at different time points of disease development using the Quantitative Real-time PCR technique (qRT-PCR). Comparison of data showed that PR2 and PAL were significantly over expressed in infected resistant and susceptible plants as against their lower expression in controls,. Upregulation of these defense-related genes during Pg and Bg infections was companied with a slow development of disease symptoms at the time course in the resistant genotype. qRT-PCR analysis revealed higher gene expression in resistant barley plants inoculated with Pg as compared with Bg, with a maximum expression for PR2 (13.8 and 5.06-fold) and PAL (14.8 and 4.51-fold) respectively, at the latest stage of each disease development. It was also noteworthy that PR2 and PAL genes, had higher constitutive expression and faster induction for the both pathogens in the resistant genotype as compared with the susceptible one. Obtained results suggest that both genes, PR2 and PAL, positively regulate Pg- and Bg-resistance in barley plants during disease progress. These expression patterns can provide useful insights to better understanding of the barley–fungus interactions with different fungal lifestyles