Antiviral Activity of Clove Oil Nanoemulsion Against Potato virus-Y (PVY)

The inhibitory effect of clove essential oil nanoemulsion on Potato virus-Y (PVY) was studied in vitro and in vivo using two concentrations (5 and 10%). In vitro study, inoculum was mixed with the inhibitor and left to stand for 1, 2 and 3 days at (23±2°C) before plant inoculation. In vivo study, plants were sprayed with the inhibitor 1, 2 and 3 days either after or before inoculation. Chenopodium quinoa plants were used as a local lesion host, while Lycopersicon esculentum seedlings were used as a systemic host. In all cases clove oil nanoemulsion had a significant inhibitory effect on PVY infection either in vitro or in vivo trials. The highest inhibitory effect was achieved in vitro when the inoculum was mixed with the inhibitor at conc. of 10% for three days before inoculation, the local lesion development and the systemic infection were inhibited by 90% and 84.2%, respectively. In the case of in vivo experiments, the highest percentage of inhibition was detected when the plants were sprayed with the inhibitor at the same concentration three days before inoculation (81.6 and 80%, respectively). Moderate inhibitory effect was recorded either in vitro or in vivo, when the inoculum was neither mixed nor sprayed with the inhibitor for two days pre-virus inoculation. Whereas, the lowest inhibitory effect was detected when the inoculum was mixed with the inhibitor for one day before inoculation. ELISA test was used to confirm the results in all cases. Also all treatments gave a significant increase in photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids), total phenols and flavonoids compared with the infected control plants. RT-PCR technique was used to evaluate the inhibitory potential of the two concentrations of clove oil nanoemulsion tested against PVY infection. It was found that the effect of this antiviral agent was concentration dependent. Clove oil nanoemulsion showed strong virucidal activity as band intensity which was the lowest at conc. of 10% when it was mixed with the virus inoculum. The results of this work illustrate, clove essential oil nanoemulsion seems to be a promising tool as an antiviral agent against Potato virus-Y on tomato plants.