Exogenous application of dsRNAs targeting multiple genes of cucumber mosaic virus in Cucumis sativus significantly reduces the viral titre

Worldwide, cucumber mosaic virus (CMV) causes significant damage to cucurbits and other horticultural crops resulting in huge economic losses. RNA interference (RNAi) based technology widely used for control of plant viruses is also an effective strategy to combat CMV infection in crop plants. In the present study, topical application of in vitro synthesized dsRNA simultaneously targeting coat protein (CP), RNA-dependent RNA-polymerase (RdRp-2a) and silencing suppressor (2b) genes was tested for virus suppression by triggering RNAi in the host plants. Cucumber seedlings mechanically co-inoculated with dsRNA and the CMV showed 100% resistance against CMV infection till the 7th day of post inoculation (Symptom Score 0). Furthermore, this foliar treatment delayed the systemic spread of CMV infection up to 21 days post inoculation. In contrast, control plants displayed disease symptoms starting from the 5th day of post inoculation (Symptom Scale 1). The vaccinated plants showed significant reduction in symptoms (51.15%) at 14 days post inoculation (dpi) and (29.9%) at 21 dpi. Absolute quantitative Real-time PCR indicated a reduction in viral titer in the dsRNA applied cucumber plants compared to the control plants. For the first time, we report here an RNA-based vaccination strategy through foliar application of dsRNA for the successful and reliable control of Cucumber mosaic virus in its native host plant cucumber.