Clothianidin-induced sublethal effects and expression changes of vitellogenin and ecdysone receptors genes in the melon aphid, Aphis gossypii

The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae) is a major pest affecting plants of Cucurbitaceae family worldwide. Clothianidin has been broadly used for the control of this insect pest. In this study, we investigated the impact of clothianidin on the demographical traits and expression changes of vitellogenin and ecdysone receptors genes in A. gossypii after exposure to the low or sublethal concentrations (LC15 and LC5, respectively). The two concentrations of clothianidin did not affect the adult longevity and fecundity of parental aphids (F-0). However, the developmental duration of 3rd instar nymph, pre-adult stage, and total pre-ovipositional period (TPOP) were increased significantly in F-1 individuals when F o was exposed to the LC15 of clothianidin. In contrast, the adult longevity and fecundity of progeny generation were decreased by the LC15. Similarly, the net reproductive rate (R-0) and gross reproduction rate (GRR) were also reduced significantly in the LC15 treated group. However, no significant effects were observed for the intrinsic rate of increase (r), finite rate of increase (lambda) and mean generation time (T). Furthermore, the expression level of vitellogenin receptor gene significantly decreased by 24.9 and 56.9% in the progeny generation when F-0 was exposed with LC5 and LC15 of clothianidin, respectively. Moreover, the ecdysone receptor mRNA expression was also reduced by 29.2 and 46.1% in the LC5 and LC15 treated groups, respectively. These results indicated that clothianidin at low or sublethal concentrations adversely affect the development and reproduction of progeny generations and effects may be related to the down-regulation of VgR and EcR genes in A. gossypii.