First results of the virome of Scaphoideus titanus, Frankliniella occidentalis and Thrips tabaci

A drastic reduction in the use of chemicals and pesticides in agriculture requires new sustainable biocontrol strategies to restrain pathogen multiplication and virulence in plants. VIROPLANT is a EU-funded research project whose primary objective is to propose viruses as potential biocontrol agents of some specific plant diseases spread in Europe. As a first step, RNAseq was applied to characterize the virosphere of Scaphoideus titanus, vector of Flavescence dorée phytoplasma, Frankliniella occidentalis and Thrips tabaci, vectors of Tomato spotted wilt virus and Onion yellow spot virus, respectively. Populations of S. titanus were collected from Italy, France, Switzerland, Hungary, and the USA. All European samples presented the same unclassified dsRNA virus and a previously uncharacterized densovirus. A new iflavirus was occasionally found in some Italian and French insects. The USA samples were richer in viral biodiversity, as members of the families Bunyaviridae, Nodaviridae, Partitiviridae, Reoviridae and Permutotetraviridae were identified. Samples of F. occidentalis and T. tabaci were collected from seven Italian regions and from two laboratory populations from the USA. Overall, full-length genomes of more than 40 new viral species were assembled. Among them, a densovirus and a mesonivirus were highly prevalent in F. occidentalis, while a virga-like and a dimarhabdovirus were present in all the T. tabaci samples. Some of the identified viruses will be selected to measure their effects on insect fitness parameters and transmission efficiency. The most promising one for each pathosystem will be used to promote virus-induced gene silencing and interfere with gene expression of the host.