Delivery of dsRNA to plant vascular tissues as a pest management approach for phloem feeding insects

Potato psyllids (Bactericera cockerelli) are a major pest of most plants in the Solanaceae family. An emerging concern with this insect is the transmission of Candidatus Liberibacter solanicearum, the pathogen that causes Zebra chip disease to the potatoes. Utilizing molecular biology, RNA interference can be used as an effective biological control method. Post transcriptional regulation by RNA interference (RNAi) is an effective technique for gene silencing. One of the mechanisms of RNAi occurs when double stranded RNA (dsRNA) is introduced to the cell, at which point it is enzymatically cleaved into short interfering RNA (siRNA) by Dicer.  These siRNAs’ are processed by the RNA-induced silencing complex (RISC). The siRNAs’ in RISC then bind to complimentary sequences on mRNA, signaling their enzymatic degradation. dsRNA for siRNA production is sequence specific and can be extracellular, because of this short synthetic dsRNA can be introduced into the cell in order for down regulation of a specific gene in a target insect. In this study, dsRNA was introduced to the roots of potato plants and insects were allowed to feed at location 20cm from point of inoculation. Once the RNA was absorbed, it travelled throughout the plant's vasculature where a target insect then ingested the fluids from the phloem of the plant, transferring the dsRNA. Viability of dsRNA uptake through plants as a method to deliver the siRNA to the potato psyllid was determined and down-regulation of target genes was assessed.