Genetic distinctions among the Mediterranean and Chinese populations ofBemisia tabaciQ biotype and their endosymbiontWolbachiapopulations

The sweetpotato whitefly,Bemisia tabaci, is a cryptic species complex composed of more than 24 different biotypes around the world. The Q biotype ofB. tabaci, which is thought to have originated in the Mediterranean Basin, is now a widespread and serious agricultural pest. In this study, the genetic differences among Q biotype populations from Mediterranean countries and China were investigated. Based on their mt COI gene sequences, the Q biotype populations could be divided into two groups, which were labelled as MedBasin 1 and MedBasin 2. MedBasin 1 is indigenous to the western Mediterranean area while MedBasin 2 is indigenous to the eastern Mediterranean area. Genetic variation was greater in the MedBasin 1 populations than in the MedBasin 2 populations. Unlike the introductions into the USA, which involved both Medbasin1 and MedBasin2 populations, allB. tabaciQ biotype populations in China belonged to MedBasin 1.Wolbachiadetection in eight representative Q biotype populations from China, Egypt and Syria indicated that all of the populations were infested withWolbachia, and the infection rate of the Chinese populations (42.5%) were not significantly different from that of Egypt and Syria (51.4%). Phylogenetic analysis indicated that the evolution of theWolbachiapopulations was not closely linked with the evolution of theirB. tabacihosts.