Ocimum basilicum-Mediated Synthesis of Silver Nanoparticles Induces Innate Immune Responses against Cucumber Mosaic Virus in Squash

Ahmed Abdelkhalek; Hamada El-Gendi; Fatimah O Alotibi; Abdulaziz A Al-Askar; Toufic Elbeaino; Said I Behiry; Kamel A Abd-Elsalam; Hassan Moawad

doi:10.3390/plants11202707

Ocimum basilicum-Mediated Synthesis of Silver Nanoparticles Induces Innate Immune Responses against Cucumber Mosaic Virus in Squash

Plants (Basel). 2022 Oct 13;11(20):2707. doi: 10.3390/plants11202707.

Authors

Ahmed Abdelkhalek¹, Hamada El-Gendi², Fatimah O Alotibi³, Abdulaziz A Al-Askar³, Toufic Elbeaino⁴, Said I Behiry⁵, Kamel A Abd-Elsalam⁶, Hassan Moawad⁷

Affiliations

¹ Plant Protection and Biomolecular Diagnosis Department, ALCRI, City of Scientific Research and Technological Applications, New Borg El Arab City 21934, Egypt.
² Bioprocess Development Department, Genetic Engineering and Biotechnology Research Institute, City of Scientific Research and Technological Applications, New Borg El-Arab City 21934, Egypt.
³ Department of Botany and Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
⁴ Istituto Agronomico Mediterraneo di Bari (CIHEAM-IAMB), Via Ceglie 9, Valenzano, 70010 Bari, Italy.
⁵ Agricultural Botany Department, Faculty of Agriculture (Saba Basha), Alexandria University, Alexandria 21531, Egypt.
⁶ Plant Pathology Research Institute, Agricultural Research Centre, Giza 12619, Egypt.
⁷ Agriculture Microbiology Department, National Research Centre, Cairo 12622, Egypt.

Abstract

Cucumber mosaic virus (CMV) causes a significant threat to crop output sustainability and human nutrition worldwide, since it is one of the most prevalent plant viruses infecting most kinds of plants. Nowadays, different types of nanomaterials are applied as a control agent against different phytopathogens. However, their effects against viral infections are still limited. In the current study, the antiviral activities of the biosynthesized silver nanoparticles (Ag-NPs) mediated by aqueous extract of Ocimum basilicum against cucumber mosaic virus in squash (Cucurbita pepo L.) were investigated. The prepared Ag-NPs were characterized using scanning electron microscopy (SEM), dynamic light scattering (DLS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and zeta potential distribution techniques. DLS, SEM, and TEM analyses showed that the Ag-NPs were spherical, with sizes ranging from 26.3 to 83 nm with an average particle size of about 32.6 nm. FTIR identified different functional groups responsible for the capping and stability of Ag-NPs. The zeta potential was reported as being -11.1 mV. Under greenhouse conditions, foliar sprays of Ag-NPs (100 µg/mL) promoted growth, delayed disease symptom development, and significantly reduced CMV accumulation levels of treated plants compared to non-treated plants. Treatment with Ag-NPs 24 h before or after CMV infection reduced CMV accumulation levels by 92% and 86%, respectively. There was also a significant increase in total soluble carbohydrates, free radical scavenging activity, antioxidant enzymes (PPO, SOD, and POX), as well as total phenolic and flavonoid content. Furthermore, systemic resistance was induced by significantly increasing the expression levels of pathogenesis-related genes (PR-1 and PR-5) and polyphenolic pathway genes (HCT and CHI). These findings suggest that Ag-NPs produced by O. basilicum could be used as an elicitor agent and as a control agent in the induction and management of plant viral infections.

Keywords: CMV; basil; defense-related enzymes; gene expression; silver nanoparticles; squash.

Grants and funding

RSP-2021/114/King Saud University