عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Viroids are pathogenic RNAs in plants without protein encoding capacity. Seven viroids belonging to four genera in the Pospiviroidae family have been reported from citrus species. By constructing the infectious clones of citrus viroids, it was possible to carried out their pathogenicity test. Full-length genome of CEVd, HSVd, CBCVd, CDVd, CVdV and CBLVd was separately amplified in RT-PCR using total RNA extracted from a Moro blood orange plant and resulting PCR products were sequenced. The full-length genome of each viroid was inserted under the control of cauliflower mosaic virus 35S promoter in a pBin62SK binary vector. Pathogenicity of viroids was tested by agroinoculation of their infectious clones to cucumber (Cucumis sativus), tomato (Solanum lycopersicum) and trifoliate orange (Poncirus trifoliata). Three weeks after inoculation, viroids were detected in newly grown leaves of inoculated plants by RT-PCR using specific primers and by dot blot hybridization using viroid specific probes. Five weeks after inoculation, symptoms including little leaf, mottling and epinasty by CVdV and CBCVd, mottling by CDVd, and epinasty and leaf deformation by CEVd, HSVd and CBLVd in tomato leaves were observed. Mechanical inoculation of infected sap of infected tomato plants induced similar symptoms in healthy tomato plants. Identification of the viroids in newly grown leaves of inoculated plants indicated the infectiousness of the generated constructs. Infectious clones of CEVd, HSVd and CBCVd were previously made, but it is the first report of the construction of the infectious clone for CDVd, CBLVd and CVdV.