The Role of Salicylic Acid in Stimulating Acquired Systemic Resistance in Tomato Plants Against Infection with Cucumber mosaic virus

Abstract

The effect of salicylic acid (SA) on the induction of systemic acquired resistance (SAR) in tomato plants against infection with Cucumber mosaic virus (CMV) was investigated. Plants treated with two concentrations of 1 and 2 mM of salicylic acid, using two application methods, spraying and irrigation, three days before mechanical inoculation with the virus, during the fall of 2022 in Tartous Governorate, Syria. The effect of acquired systemic resistance was assessed by: time required for symptoms development, disease severity, concentration of free salicylic acid and peroxidase activity in experimental plants. The results obtained showed that treatment with salicylic acid delayed the appearance of symptoms of viral infection by up to 21 days compared to 12 days for the control, and reduced disease severity by 38.3% in the sprayed treatment at a concentration of 2 mM compared to the rest of the treatments. The value of free salicylic acid increased to 124.5 μg/g compared to the healthy control (21.54 μg/g) and the infected plants not treated with salicylic acid (13.73 μg/g). In addition, the peroxidase enzyme concentration increased to 0.209 μmol/mg compared to the healthy control (0.112 μmol /mg), at the time when enzyme activity of infected plants not treated with salicylic acid reached 0.044 μmol/mg. An increase in the content of free salicylic acid and peroxidase activity, a delay in the onset of infection symptoms, and decrease in the disease severity were good indicators for the induction of acquired systemic resistance as a result of treatment with salicylic acid.

Keywords:

Salicylic acid, systemic acquired resistance, Cucumber mosaic virus, tomato.