Prevalence, symbiosis with Rickettsia, and transmission of Tomato yellow leaf curl virus of invasive Bemisia tabaci MED Q2 in Japan

Abstract The whitefly, Bemisia tabaci, is a notorious insect pest that transmits plant pathogenic viruses to a wide range of economically-important crops. An invasive genetic group of B. tabaci, Mediterranean Q2 (MED Q2), has recently spread to Europe, USA, and Asia. In this study, we investigated the prevalence of MED Q2 in Japanese agricultural sites and found that its distribution has expanded since it was first detected in 2013. Polymerase chain reaction analysis revealed that all MED Q2 individuals were infected with Rickettsia. Rickettsia titres increased during nymphal development, presumably in response to the nutritional needs of the host. Fluorescence in situ hybridisation analysis revealed that Rickettsia was densely located near Portiera-containing bacteriocytes at all growth stages. Rickettsiamay therefore play an important role, such as supplying nutrients to the host, in cooperation with Portiera. Transfer experiments indicated that MED Q2 was as effective a vector for Tomato yellow leaf curl virus as MED Q1 and is therefore a high-risk agricultural pest. These results provide important insights into the biology and ecology of the invasive MED Q2 to effectively control its spread and minimise its impact on crops.