Control of cucumber mosaic virus in rockmelon using dsRNA-mediated silencing of coat protein and movement protein genes with no deleterious effect on plant phenotype

Abstract

Rockmelon is a popular tropical fruit with high nutritional value. Cucumber mosaic virus (CMV), an aphid-transmitted virus, causes severe damage to rockmelon production. Exogenous application of double-stranded RNA (dsRNA) targeting viral sequences has shown promising results in controlling viral infection but has not been reported for CMV in rockmelon. In the current study, the protective effect of exogenous dsRNAs targeting the CMV coat protein (CP) and movement protein (MP) was tested in rockmelon. The effectiveness of dsRNA-mediated protection was measured by disease severity index (DSI) and compound enzyme-linked immunosorbent assay. The individual dsRNA CP and MP treatments each showed protection by reducing the DSI and virus titre, whilst a combination of dsRNA of CP and MP treatment showed much lower DSI (4.31-fold lower) and virus titre (4.91-fold lower) compared to CMV-inoculated plants without dsRNA treatment. Chlorophyll content, relative water content, plant height and number of leaves were not significantly different between virus challenged dsRNA-treated and mock-inoculated plants. Based on the DSI, two applications containing 9000 ng of dsRNA CP and MP in combination showed maximum CMV protection. Taken together, these results indicate that exogenous treatment containing a combination of dsRNA of CP and MP can control CMV infection in rockmelon.