Exogenous application of coat protein-specific dsRNA inhibits cognate cucumber mosaic virus (CMV) of ghost pepper

Cucumber mosaic virus (CMV) is the major virus infecting ghost pepper (interspecific hybrid between Capsicum chinense and C. frutescens ) that causes considerable yield losses. We hypothesized that the exogenously applied double-stranded RNA (dsRNA) in plants can mimic the viral RNA gene that facilitates in-planta virus replication and trigger post-transcriptional gene silencing via the RNAi pathway. The specific objectives of this study were to develop a dsRNA construct for CMV resistance in ghost pepper and to conduct a proof-of-concept study on CMV silencing in ghost pepper using exogenously applied dsRNA targeting the CMV coat protein (CP). CMV-infected leaf samples were collected from ghost pepper fields and CMV infection was confirmed by RT-PCR. In vivo production of dsRNA was successful in E.coli with the use of T7 RNA polymerase. To investigate resistance induction against CMV, crude extracts of dsRNA derived from CMV-CP gene (dsRNA_ CMV-CP) expressed in E. coli were exogenously applied with CMV onto healthy ghost pepper plants and compared with plants inoculated with CMV alone. Exogenously applied dsRNA on leaves inhibited CMV severity on ghost pepper plants relative to plants inoculated with CMV alone. Thus, exogenous application of dsRNA molecules derived from CMV CP gene can be a novel tool to suppress CMV and improve yield in these peppers.