RNA delivery for Trans-Kingdom RNAi using two Plant Systems for the control of Cotton Bollworm (Helicoverpa armigera)

Supervisors: Dr Julia Bally and Dr Samanta Bolzan De Campos

The cotton bollworm (Helicoverpa armigera) is one of the most destructive insect pest species globally, causing severe crop damage resulting in billions of dollars in economic losses. Although control methods, including synthetic and organic insecticides, have been employed, resistance has been observed, while the controversial nature of genetically modified crops has hindered the widespread use of these varieties. Consequently, target gene silencing by RNA interference (RNAi) has emerged as a promising alternative for managing insect pests, offering a sustainable and long-term solution to this ongoing challenge. Here, we examined the effects of feeding-based RNAi treatments on cotton bollworm larvae reared on different host plant systems. This was accomplished by delivering double-stranded RNA (dsRNA), targeting important insect genes, to Nicotiana benthamiana and Cos lettuce plants using two different treatment methods (S and V) and conducting a feeding bioassay. The results revealed that the highest mortality rates occurred in larvae consuming Cos lettuce treated with treatment S, with the larvae exhibiting an 82.57% mortality rate. Furthermore, larvae ingesting plants treated with treatment S generally displayed a reduction in weight compared to those fed with treatment V. In general, treatment S led to higher mortality rates and reduced larval weight, and appeared to be particularly effective when applied to Cos lettuce as opposed to N. benthamiana. These findings demonstrate the potential of RNAi as a viable strategy for controlling cotton bollworm and highlight the importance of selecting the appropriate delivery system and host plant.