Abstract

Tobacco cutworm, Spodoptera litura (Fabricius) is the major constraint for the production and productivity of several agricultural and horticultural crops. The most common and effective method for the management of S. litura is the use of insecticides. However, the extensive use of insecticides leads to environmental pollution, contamination of food materials and development of resistance in insect pests. Hence, there is an urgent need for the development of effective and alternative pest management strategy. Post-transcriptional gene silencing or RNA interference (RNAi) approach was found as an environmentally safe and effective method for the management of several lepidopteran and coleopteran insect pests. Thus, the present study was focused onthe design of double-stranded RNA (dsRNA) mediated knockdown strategy for the management of S. litura targeting chitin synthase (SlCHSA) gene. In this study, the SlCHSA gene specific dsRNA was synthesized and assessed their effect on growth and development of S. litura under in vitro conditions. Comparatively lower larval body weight and moulting rate was observed on the larvae fed with dsSlCHSA treated leaves than in untreated leaves. The moulting rate was recorded as 26.67 per cent where, the larvae fed with dsSlCHSA treated leaves during 4th moult. The result of the RT-qPCR analysis showed less expression level (6.25 fold) of SlCHSA on larvae fed with dsSlCHSA compared to control. The results suggested that SlCHSA can be used as a good candidate gene for RNAi based insect pest control. The enhancement of expression level of dsSlCHSA can be studied through plant mediated RNAi for developing an effective RNAi strategy against S. litura.

Keywords: Spodoptera litura, Chitin synthase A (CHSA), dsRNA and RNAi approach.