Viral disease control in strawberry plants: A potential impact of green nanotechnology

Abstract

Aims: Strawberry (Fragaria ananassa Duch.) is a member of the family Rosaceae and one of the most important vegetable crops in Egypt for local fresh consumption and exportation. Suspected symptoms of Strawberry mild yellow edge virus (SMYEV) on naturally infected strawberry plants were observed in Al Qaluobia Governorate. The main goal of this study was to develop a novel eco-friendly biogenic silver nanoparticle using clove (Syzygium aromaticum) (Sz-AgNPs) aqueous extract to control viral infection. Methodology and results: Mechanically inoculated sixteen plant species representing seven families, Apocynaceae, Chenopodiaceae, Cucurbitaceae, Fabaceae, Moraceae, Rosaceae and Solanaceae, were used as hosts for SMYEV. Systemic mosaic, chlorotic local lesions, vein clearing, marginal chlorosis, marginal necrosis, yellowing and vein banding were observed 7 to 20 days post-inoculation. Transmission electron microscopy (TEM) of diseased tissues revealed severe degeneration of the chloroplasts and nucleus structures and the formation of cell wall protrusions. Sz-AgNPs were characterized using UV-Vis spectroscopy, TEM, dynamic light scattering (DLS) and Fourier transform infrared (FTIR). Foliar application of Sz-AgNPs (200 µg/mL) 24 h post and/or concurrently with SMYEV inoculation dropped the infection rate by 90% and 55%, respectively, whereas it was only reduced by 35% when applied 24 h prior to viral inoculation compared to control groups. DAS-ELISA and RT-PCR verified SMYEV inhibition (75-90%) in all plants treated with 200, 150 and 100 µg/mL Sz-AgNPs 24 h post-viral inoculation. Complete viral eradication was attained by applying Sz-AgNPs at a concentration of 200 μg/mL 24 h post-virus inoculation. Moreover, the total phenols, indoles, Vitamin C, total flavonoids and citric acid contents were not significantly affected by Sz-AgNPs treatment compared to healthy control groups. Conclusion, significance and impact of study:In conclusion, Sz-AgNPs suppressed SMYEV by 75-90% when applied 24 h post-virus inoculation. Eco-friendly Sz-AgNPs could be used for controlling viral infections and avoiding the rejection of exportable strawberries due to the use of harmful pesticides.