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he 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.

he effects of essential oils of clove and fennel seeds and their major components as foliar spray were screened for inducing resistance against Potato Virus Y in vivo in both systemic and local lesion hosts at different concentrations. Clove oil at conc. of 15% gave the highest inhibitory effect against PVY infection than fennel oil. The inhibition percentages were 85, 80 % in pepper as a systemic host and up to 90, 87 %, respectively in Chenopodium amaranticolor as a local lesion host when applied 48 hrs before virus inoculation. Whereas, the inhibitory effect was less pronounced when essential oils were sprayed on the tested plants 24 hrs before virus inoculation. However, the severity of symptoms was assessed by visual inspection. ELISA test was used to confirm the results in all cases. When the major components of essential oils were applied individually, Eugenol gave the highest inhibitory effect (90%) on PVY-systemically infected pepper plants and 91.8% on Ch. amaranticolor as local infected plants when applied 48 hrs before virus inoculation followed by Anethol. While, Limonene was less effective in reduce PVY infection. Considerable increase in total protein content in pepper plants sprayed with essential oils and their major components before virus inoculation was recorded compared with healthy and infected control plants. Moreover, SDS-PAGE revealed a new protein band 20 KDa which was found only in pepper plants sprayed with clove oil at conc. of 15%. Also new proteins 19, 20 KDa and 25 KDa were found only in pepper plants sprayed with Eugenol. It has been suggested that, the induced proteins may help to limit virus spread or multiplication.

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Plant viruses are a global concern for sustainable crop production. Among the currently available antiviral approaches, nanotechnology has been overwhelmingly playing an effective role in circumventing plant viruses. Alfalfa mosaic virus (AMV) was isolated and identified from symptomatic pepper plants in Egypt using symptomatology, serological tests using the direct ELISA technique, differential hosts and electron microscopy. The virus was biologically purified from a single local lesion that developed on Chenopodium amaranticolor. The AMV infection was further confirmed using an AMV coat protein-specific primer RT-PCR. We further evaluated the antiviral potential of chitosan nanoparticles (CS-NPs) and chitosan silver nanocomposites (CS-Ag NC) in different concentrations against AMV infections in pepper plants. All tested concentrations of CS-NPs and CS-Ag NC induced the inhibition of AMV systemically infected pepper plants when applied 24 h after virus inoculation. The foliar application of 400 ppm CS-NPs or 200 ppm CS-Ag NC produced the highest AMV inhibitory effect (90 and 91%) when applied 24 h after virus inoculation. Treatment with CS-NPs and CS-Ag NC considerably increased the phenol, proline and capsaicin contents compared to the infected plants. Moreover, the agronomic metrics (plant height, fresh and dry pod weights and number of pods per plant) were also significantly improved. According to our results, the potential applications of CS-NPs and CS-Ag NC may provide an effective therapeutic measure for better AMV and other related plant virus management.