Molecular evaluation of the principal Ranunculus asiaticus L. viruses

The buttercup (Ranunculus asiaticus L.) belongs to the family Ranunculaceae and is a popular ornamental plant cultivated for the sale of cut flowers and for the production of potted or border plants. This species is native to the eastern Mediterranean basin and has become widespread in Western Europe, South Africa, California, Israel and Japan. The hybrids of Ranunculus asiaticus are susceptible to infection by several viruses, very often present in mixed infection, and all associated with economically important diseases. The main viral species that infect the buttercup are: Tomato spotted wilt virus (TSWV, genus Tospovirus), Impatiens necrotic spot virus (INSV, Tospovirus), Ranunculus white mottle virus (RWMV, Ophiovirus), Cucumber mosaic virus (CMV, Cucumovirus), Tobacco mosaic virus (TMV, Tobamovirus), Tobacco rattle virus (TRV, Tobravirus), Tobacco necrosis virus (TNV, Tombusvirus); moreover, several viral species listed in Potyvirus genus were detected: Potato virus Y -Ranunculus strain (PVY-R), Turnip mosaic virus (TuMV), Ranunculus leaf distortion virus (RLDV), Ranunculus mild mosaic virus (RMMV), Ranunculus mosaic virus (RMV) and Ranunculus latent virus (RLV, Potyviridae, Macluravirus). Although the serological diagnosis (ELISA) is in many ways sufficient for the identification of viruses and for the diagnosis of viral diseases, it may find serious limitations in the case of viruses with low titer in the natural host. For this reason molecular analysis has been widely used as a highly sensitive and specific detection method. In the present study, the main viruses infecting Ranunculus hybrids, grown in greenhouse in the Liguria region (Imperia province), will be evaluated by double step RT-PCR assays and specific primers, in comparison with ELISA, using leaf tissues as starting material. Preliminary results show the presence of some viral species (TSWV, RLDV, RMV) in the samples analyzed, either in single or in mixed infection, and confirm that the molecular evaluation, due to versatility of use and reliability of results, can be easily used as a tool for viruses detection on large scale propagation materials in order to prevent the spread of the principal viruses and assure the production of virusfree Ranunculus plants.