Natural infection of croton yellow vein mosaic virus and its cognate betasatellite in germplasm of different Crambe spp in India.

Crambe is an important crop grown worldwide for industrial oil and seed meal. Besides the fungal and bacterial diseases, the crop is reported to be infected by tobacco mosaic virus, beet western yellows virus and turnip mosaic virus under experimental condition. Till now, there was no report of natural infection of any begomovirus in this crop. In the present study, a leaf curl disease was observed in germplasm accessions of three species of Crambe (C. abyssinica, C. glabrata and C. hispanica). Based on the symptoms and presence of whitefly population in the field, begomovirus infection was suspected. Molecular characterization through RCA approach, indicated presence of croton yellow vein mosaic virus (CYVMV, KJ747958) and croton yellow vein mosaic betasatellite (CroYVMB, KM229762). Co-agroinoculation of partial dimeric construct of CYVMV with complete dimeric construct of CroYVMB, produced typical leaf curl symptoms in C. abyssinica, whereas, agroinoculation of partial dimeric construct of CYVMV alone could not produce symptoms in the same plant. In contrast, the CYVMV construct alone could produce symptom in Nicotiana benthamiana, a model host for plant virus studies. In N. benthamiana co-inoculation of CroYVMV with CYVMV construct develop more severe symptoms. However, neither the CYVMV construct alone nor the co-inoculation with CroYVMB produce any symptom in Arabidopsis thaliana even with different methods of inoculation. Inoculated Arabidopsis thaliana also did not yield any amplification of the virus as assessed through PCR and rolling circle amplification (RCA). Thus it confirmed that for successful infection in crambe, CYVMV requires betasatellite, while in N. benthamiana, it does not require betasatellite for symptom induction and in Arabidopsis thaliana CYVMV alone or in presence of betasatellite did not replicate and produce any symptom. This study constitutes the first confirmed record of natural infection of a begomovirus in crambe and further confirmed that cognate betasatellite of CYVMV has differential role in infectivity in different hosts.