Management of Helicoverpa armigera via plant-mediated RNA interference, progresses and challenges

Abstract

Cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera Noctuidae) is a major agricultural pest that causes significant yield losses of crop plants each year. In the past few decades, the potent approaches of H. armigera control, including chemical insecticides and Bacillus thuringiensis (Bt) toxins, have been constrained due to health hazards, environmental contamination, and development of resistance, after their extensive application. Thus, there is need to find alternative strategies for H. armigera management. Expression of insect-targeted RNA interference (RNAi) constructs in host plants has emerged as one of such a novel and environment friendly strategies. However, various factors, such as highly active nucleases and high pH in the midgut, as well as failure of small interfering RNA to escape the endosome, lead to relatively low RNAi efficiency in lepidopteran insects. Although most plant-mediated RNAi experiments compromised insect development and growth of H. armigera, full protection of transgenic plants against H. armigera was not achieved and no commercially available product has yet been developed for H. armigera control. A clear understanding of the current status of RNAi utilization in H. armigera control is critical for improving its efficiency. In this review, we summarize the recent advances in plant-mediated RNAi for H. armigera control, including target gene selection, double stranded RNA or artificial microRNA expression from nuclear or plastid genome, and protection of RNAi molecules from degradation by nucleases. Additionally, we highlight factors influencing the efficacy of plant-mediated RNAi, and discuss the future research of this plant genetic engineering strategy for achieving effective management of H. armigera.