RNAi in Tuta absoluta management: effects of injection and root delivery of dsRNAs

The South American tomato pinworm, Tuta absoluta, is considered worldwide as one of the most important tomato pests. Insecticide resistance reported on the moth and the awareness about the negative impact of agrochemicals on the environment and human health have raised the demand for new control tools. Among these, RNA interference (RNAi) can represent a valid tool to be included into new control strategies against this pest. Here we report the results of trials aimed at evaluating the effects of dsRNAs targeting acetylcholinesterase (AChE), nicotinic acetylcholine alpha 6 (nAChRs), ryanodine (RyRs) receptors by injection and root delivery. In the injection procedure, 2 and 5 µg of dsRNA were able to reduce the gene expression in a range of 62.7–75.4%, inducing a maximum mortality rate of 92.59%. The dsRNAs administered at 5 µg by root absorption revealed the potential of this delivery system to affect the gene expression (47–69% reduction) and the mortality (ranging from 67.1 to 80.5%) of treated specimens. The delivered dsRNAs (both injected and root administered) affected the weight of both T. absoluta pre-pupae and pupae. The selected AChE, nAChRs and RyRs genes can be suitable targets for T. absoluta control by means of in planta delivery dsRNAs.