Study of PR gene expression and activity of effective enzymes in induced resistance to powdery mildew by salicylic acid

Powdery mildew caused by Podosphaera xanthii is a common and serious foliar disease in Cucurbitaceae. In this study, salicylic acid was used in two concentrations (0.1 and o.5 mM) and distilled water as control. After 24 hours post treatment, plants inoculated with 50 μl fungi spore suspensions (at a concentration of 105 conidia ml-1) with dotting procedure and then plants incubated in green house conditions. Molecular analysis showed increased expression of PR-1 in 24, 48 and 72 hours after inoculation. The analyses of antioxidant enzyme activities in stressed plants showed that the concentrations of 0.1 and 0.5 mM salicylic acid significantly increased the activity of GPX, 48 and 72 hours and PAL, 72, 168 and 240 hours post inoculation.