Topical Application of Cocktail dsRNA Induces Plant Resistance Against Bean Common Mosaic Virus (BCMV)

Bean common mosaic virus (BCMV) is a severe plant pathogen of common bean (Phaseolus vulgaris L.), that causes huge yield losses across the globe. The virus has a wide host range and varied modes of transmission, due to which its management is challenging. Pathogen-derived resistance, which entails inserting virus-derived gene sequences into transgenic plants, is extremely effective in overcoming plant viruses. However, owing to ethical and biosecurity concerns, transgenic crops have not been widely accepted. Exogenous application of double-stranded RNA (dsRNA) is a new and intriguing method for inducing resistance against plant viruses. In this study, the efficacy of exogenous application of dsRNAs synthesized from BCMV helper component proteinase (HC-Pro) and coat protein (CP) genes were assessed in three plants: tobacco (Nicotiana tabacum), common bean (Phaseolus vulgaris L.), and cowpea (Vigna unguiculata), and both dsRNAs elicited a resistance response. dsRNA targeting the HC-Pro gene of BCMV was found more effective in inducing RNAi-based resistance than dsRNA targeting the CP gene of BCMV with a more pronounced effect in cowpea than tobacco and common bean. We showed the stability and transport of both dsHC-Pro and dsCP in inoculated to non-inoculated young leaves. We also showed the ability of mesoporous silica nanoparticles (MSP) conjugated with dsHC-Pro to provide prolonged stability and broader resistance against BCMV in common bean, extending protection from 12 dpi up to 20 dpi, compared to naked dsHC-Pro. Our results suggest that dsRNA produced from HC-Pro and CP genes of BCMV can induce RNAi-based resistance against BCMV infection.