Effect of the endosymbiont Regiella insecticola on an aphid parasitoid

International audienceAbstract The importance of secondary endosymbionts on the resistance to parasitoids is increasingly recognized. Compared with Hamiltonella defensa, our understanding of the role of Regiella insecticola in protecting hosts against parasitic wasps is not well documented. In this study, we conducted experiments to determine whether R. insecticola in Sitobion avenae (the English grain aphid) could confer resistance to a parasitoid, Aphelinus asychis Walker, a major natural enemy in aphid field populations. With the genetic background controlled using clones, our results showed that infected aphids were more likely to be parasitized by A. asychis. However, compared with the uninfected controls, the weight of emerged wasps within 24 hours was significantly lower from infected aphids, suggesting that R. insecticola negatively affected the growth of the developing parasitoid larvae, although no difference in emergence rate between the treatments and the control was detected. These results will help to increase understanding of the dynamics of host-parasite-symbiont interactions