Host-induced silencing of CpCHI gene occasioned developmental abnormalities and mortality in Maize stem borer (Chilo partellus)

The RNAi-based insecticide for crop protection has witnessed a rapid improvement over the years. However, its potential to efficiently control maize stem borer ( Chilo partellus ) pest has remained unexplored. In this study, double-stranded C. partellus chitinases ( dsCHI ) toxicity was investigated on C. partellus larvae fed on an artificial diet coated with bacterially-expressed dsCHI and purified dsCHI. Furthermore, we developed transgenic Maize lines expressing dsRNA targeted against C. partellus chitinases transcripts and performed a detached leaf insect feeding bioassays. Our results revealed that the chitinase transcripts expression was significantly downregulated by 55% and 51% in the larvae fed on purified dsCHI at 5- and 15-days. Post-exposure to bacterially-expressed dsCHI resulted in 57% and 82% reduction in chitinase mRNA transcripts after 5- and 15-days. The larvae exhibited various phenotypic distortion levels across the developmental stages, and 53% mortality occurred in transgenic fed larvae compared to those fed on non-transgenic leaves. In conclusion, we have identified C. partellus chitinase gene as a potential target for RNAi mediated control and demonstrated that oral delivery via bacteria and plant-mediated delivery are viable means of achieving C. partellus RNAi mediated control.