Suppression of the ubiquitin E2 gene through RNA interference causes mortality in the banana weevil, Cosmopolites sordidus (Germar)

RNA interference (RNAi) is a natural defense mechanism triggered by double-stranded RNA (dsRNA) for protection of cells against foreign parasitic nucleic acids. The RNase III enzyme Dicer processes dsRNAs into short small interfering RNAs (siRNAs) that degrade the specific mRNA. RNAi has been demonstrated in a range of organisms including coleopterans and has a potential use in crop protection against insect pests and pathogens. In this study, we explored the use of RNAi for the control of the banana weevil that is not only the most important banana pest in East Africa, but has also eluded control through cultural, chemical and biological approaches. The ubiquitin E2 gene, essential for protein catabolism was identified, amplified and transcribed into dsRNA and fed to banana weevil larva in in vitro bioassays. The dsRNA significantly retarded banana weevil larval growth and caused up to 100% mortality at 21 days. Growth inhibition and mortality increased with dsRNA concentration (10 to 100 ng µL-1), though no significant differences were observed between the 50 and 100 ng µL-1 concentrations. We for the first time demonstrate RNAi in the banana weevil. Transgenic banana plants expressing siRNA or hairpin RNA could therefore potentially be used for controlling the banana weevil.