A single-pair method to screen Rickettsia-infected and uninfected whitefly Bemisia tabaci populations

Bacterial endosymbionts such as Rickettsia and Wolbachia play prominent roles in the development and behaviour of their insect hosts, such as whiteflies, aphids, psyllids and mealybugs. Accumulating studies have emphasized the importance of establishing experimental insect populations that are either lacking or bearing certain species of endosymbionts, because they are the basis in which to reveal the biological role of individual symbionts. In this study, using Rickettsia as an example, we explored a "single-pair screening" method to establish Rickettsia infected and uninfected populations of whitefly Bemisia tabaci MEAM1 for further experimental use. The original host population had a relatively low infection rate of Rickettsia (< 35%). When B. tabaci adults newly emerged, unmated males and females were randomly selected, and released into a leaf cage that covered a healthy plant leaf in order to oviposit F1 generation eggs. Following 6 days of oviposition, the parents were recaptured and used for PCR detection. The F1 progeny, for which parents were either Rickettsia positive or negative, were used to produce the F2 generation, and similarly in turn for the F3, F4 and F5 generations respectively; if the infection status of Rickettsia was consistent in the F1 to F5 generations, then the populations can be used as Rickettsia positive or negative lines for further experiments. In addition, our phylogenetic analyses revealed that Rickettsia has high fidelity during the maternal transmission in different generations.