Viricidal Activity of Silicon Dioxide Nanoparticles against Cowpea Aphid Borne Mosaic Virus

The management of viruses in cowpea is a challenging task and the use of nanoparticles (NPs) presents a promising opportunity for novel antiviral strategies. This study evaluates the viricidal activity of silicon dioxide nanoparticles (SiO₂NPs) against cowpea aphid-borne mosaic virus (CABMV) under controlled conditions. Silicon dioxide nanopowder formulation was used in this study. The virus, molecularly characterized as CABMV, was maintained through mechanical transmission. Pre- and post-inoculation of virus followed by NP foliar spray at different concentrations were done in local lesion host, Chenopodium amaranticolor, and propagative host, cowpea. The studies using various concentrations of SiO₂NPs on C. amaranticolor and cowpea revealed that pre- or post-inoculation of the virus combined with a foliar spray of SiO₂NPs at 1000 ppm is an effective treatment, exhibiting no local lesions compared to 34 local lesions in the viral control. In cowpea, among the various concentrations tested, foliar application of SiO₂NPs at 1000 ppm before CABMV inoculation reduced the vulnerability index (VI) to zero, followed by SiO₂NPs at 500 ppm, which achieved a VI of 2.77compared to viral control (VI – 94). The efficacy of NP treatment was further validated by assessing the viral titre using DAS-ELISA, with treated plants showing a sevenfold reduction in viral titre compared to the control. A significant reduction in the number of local lesions in C. amaranticolor and the vulnerability index in cowpea demonstrated the pronounced impact of SiO₂NPs on viral particles. Simultaneous inoculation of the virus and NPs showed reduced, diffused local lesions on leaves treated with viral sap-containing NPs, compared to a higher number of intact lesions in the control. This reduction is likely due to the disintegration of viral particles by NP treatment, leading to decreased disease severity. These findings further emphasize the potential of SiO₂ NPs in mitigating the severity of cowpea aphid-borne mosaic disease.