D3025: Plants strike back: HIGS in the battle against RNA-resistant Colorado potato beetle (Leptinotarsa decemlineata Say)

Potato (Solanum tuberosum) is critical for food security as one of the most important staple crops globally. The Colorado potato beetle (CPB, Leptinotarsa decemlineata Say) is the most important defoliator and one of the most economically devastating pests of potatoes globally. Moreover, this insect has evolved resistance to all pesticidal modes of action used in its control and is considered an originator of the modern day pesticidal treadmill. Recently, RNA pesticides have been hailed as the “perfect insecticide” due to representing a new mode of action displaying high specificity and low environmental impact. These RNA pesticides work through the activation of the RNA interference (RNAi) gene silencing response by a double stranded RNA (dsRNA). The two main delivery approaches for insecticidal dsRNAs are through sprays (exogenous, spray-induced gene silencing or SIGS) and produced by transgenic plants as “plant incorporated protectants” (endogenous host-induced gene silencing or HIGS). Currently, RNAi control of CPB is only commercially available through SIGS with Ledprona and there are currently no approved or market-ready HIGS potato plants. Potato plants transformed transplastomically have shown to be more effective against CPB due to protection from nucleases and higher accumulation of dsRNA in the chloroplast compared to nuclear expression. This study tested the efficacy of transplastomic plants expressing dsRNAs targeting actin or V-ATPase subunit A in both susceptible and a strain of CPB displaying >11,000 fold-resistance to SIGS. From this experiment we will elucidate whether previously resistant beetles to SIGS maintain resistance when exposed to HIGS.