Host plant-based variation in fitness traits and major detoxifying enzymes activity in Scirtothrips dorsalis (Thysanoptera: Thripidae), an emerging sucking pest of tea

Abstract

AbstractScirtothrips dorsalisHood is a polyphagous species and an important sucking pest of tea (Camellia sinensis) (Theaceae). The fitness traits ofS. dorsalison two alternative host plants:Capsicum annuumL. (chilli) (Solanaceae) andRicinus communis(castor oil plant) (Euphorbiaceae) and onC. sinensisand corresponding levels of defence enzymes was studied. The study revealed thatC. sinensisis the more suitable host ofS. dorsalisbased on faster development (13.6 days) compared to the alternative hosts,C. annuum(15.5 days) andR. communis(16.7 days), a higher fecundity (C. sinensis: 11.4 eggs;C. annuum: 9.7 eggs;R. communis: 8.6 eggs), and superior egg hatchability (C. sinensis, 92.6%;C. annuum: 82.5%; andR. communis: 74.6%). The host-based variation in the fitness traits ofS. dorsaliscorroborated in light of differential activity of three major detoxifying enzymes, such as the general esterases (GEs), glutathioneS-transferases (GSTs), and cytochrome P450 mediated monooxygenases (CYPs). Densitometric analysis of GEs showed five esterase isozymes (EST I–V) with retardation factor (Rf) values of 0.17, 0.22, 0.27, 0.35 and 0.52, respectively. The pixel density, and accordingly the profile height, varied in different host-specificS. dorsalis. A significant variation of the quantity of these enzymes was also apparent in the insect when reared on the three hosts. A 2.4 and 2.7, 1.6 and 2.0, and 2.0 and 2.3-fold higher GEs, GSTs and CYPs activity on the two non-tea hosts possibly signify a predisposition of the species for higher tolerance to insecticides, enabling the pest to switch to tea where synthetic insecticides are routinely used.