The Effect of Salicylic Acid and Jasmonic Acid on Disease Symptoms and Defense Genes Expression in a Greenhouse Cucumber Infected with CMV

Acquired systemic resistance (SAR) is one of the defenses that can make plants resistant to systemic viral infections. Acquired systemic resistance is associated with a hypersensitivity response in the host, and salicylic acid is known as its signal. In this study, the effect of plant inducers such as salicylic acid and jasmonic acid on cucumber viral disease with cucumber mosaic virus, CMV and the expression of some defense genes were investigated. Treatments included plants treated with CMV, salicylic acid (with a concentration of 1.5 mmol), jasmonic acid (with a concentration of 1.5 mmol), as well as salicylic acid and jasmonic with CMV. The results of this study showed that the maximum severity of CMV-induced disease was observed in plants treated only with CMV (68.85%). In the treatment of salicylic acid and jasmonic acid with CMV, the severity of symptoms was significantly reduced (10.23%). Then, the effect of these treatments on the expression of four genes Peroxidase (POX), Catalase (CAT), Superoxide Dismutase (SOD) and Phenylalanine Ammonialyase (PAL) was investigated. The results showed that the expression of these genes in treated plants had an upward trend until the ninth day after treatment. But this upward trend was much less observed in control plants (treated with water and virus). The highest level of gene expression in the studied enzymes compared to the control plant was related to the catalase enzyme (401.7 times), followed by peroxidase enzymes (266.8), superoxide dismutase (152.7) and phenylalanine ammonialyase (101.8). According to these results, salicylic acid and jasmonic acid, increased plant resistance to CMV and reduced the symptoms of the virus in cucumber plant by inducing plant defense mechanisms.