RNAi Targeting <i>Chitin synthase</i> Genes Specifically Affects Larval Performance in <i>Tuta absoluta</i>

value, TaChSA average level was much higher than that of TaChSB, allowing us to compare the mRNA levels on RNAi effectiveness. We found that ingestion of bacterially-expressed dsChSA or dsChSB for 24 h identically decreased the target mRNA levels in whole body, and in the head, epidermis, foregut and hindgut. Feeding dsChSA affected larval growth and leaf mining, caused 19.7% larval lethality and 31.6% non-emerged adults. Moreover, RNAi against TaChSA damaged rectum integrity, decreased cuticle thickness, and thinned tracheae. By contrast, ingesting dsChSB decreased larval weight, led to 3.8% larval lethality and 43.2% of resulting pupae failing to emerge. Taken together, dsChSA and dsChSB might be systemically transported, and exerted a strong RNAi efficiency irrespective of target mRNA levels. Our results indicate a possible application of bacterially-expressed dsChSA and dsChSB in the field to protect growing crops against T. absoluta.