The response to potato virus X (PVX) infection of tomato plants treated with systemic acquired resistance (SAR)- inducing elicitors

Improving the ability of the host plant to resist or withstand the attack of a pathogen, such as a virus, is prominent. Systemic acquired resistance, or simply SAR can be triggered using some biotic and abiotic factors called elicitors. This investigation aimed to characterize the effect of some elicitors inducing the SAR on tomato plants after challenge inoculations with Potato virus X (PVX). Pot experiment was established to test the exogenous foliar application of three doses of Messenger (M1= 1X, M2= 2X, M3= 0.5X) and of ISR2000 (R1= 1X, R2=2X, R3=0.5X) on the healthy plants and check their effects on viral disease development in plants infected with PVX at three different inoculating times, 48, 72 and 96 hours post treatment (hpt). Different parameters (e.g. chlorophyll content, growth parameters) were measured to assess the response to the infection exerted by elicitors of SAR in leaves and roots of tomato. The evaluations were made at three different sampling times with one week interval, and the results showed that there were some significant differences between the doses of ISR2000 and Messenger as compared to the water control, and the inoculation and sampling times significantly affected the results. The dose R2 resulted in the maximum significant increase in the chlorophyll content, plant height and leaf area after 9 days of treatment (9dpt), with the rates of 113.75%, 170.16% and 327% of the corresponding water control, respectively. Root total length was significantly increased to 254.47% after 23 days of the R3-treatment. Tomato plants inoculated 96 hours after the R2 treatment showed the maximum recovery in plant height (167.9%) and leaf area (281.11%) at sampling time of 9dpt, as compared to non-treated plants. Similarly, upon 96hpt-PVX inoculation, while R1 treatment brought about the highest significant recovery in chlorophyll content (120.1%) at sampling time of 23dpt, the increase in the root total length of the infected plants after the treatments was not significant.