Late blight, caused by the fungus Phytophthora infestans is a common foliar disease of potato worldwide. Relatively, little is known about the mechanisms of potato resistance challenged with this disease. In the present work, expression of some well-known defense-related genes viz. PR1, PR2, PR3, PR5 and StSYR1 were monitored in resistant and susceptible potato cultivars at early points of infection using quantitative real-time PCR (qPCR). The results showed significant variance in the expression patterns of the genes between resistant and susceptible potato - P. infestans interactions as compared to the non-inoculated controls. It is also noteworthy that PR3 and StSYR1 genes have a higher constitutive expression and faster induction in the resistant cultivar as compared with the susceptible one after infection with the pathogen. However, PCR (qPCR) analysis revealed higher gene expression in resistant cultivar than susceptible ones with expression for PR3 (6.1 and 2.5-fold) and StSYR1 (8.1 and 2.4-fold), respectively, at 72 hours post inoculation. Our results might supply crucial information concerning potato signaling events that accounts for classical expression gene changes induced by P. infestans invasion.
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