Characterization of an Indian isolate of Carnation mottle virus infecting carnations

摘要

Carnation (Dianthus caryophyllus L.) is an important cut-flower crop. It is susceptible to infection by several viruses, which cause significant losses to all types of carnations. Carnation mottle virus (CarMV) is one of the most important viruses among them. Ninety-three carnation cultivars collected from different parts of India were screened serologically with DAS-ELISA using polyclonal IgG. About 90% of the cultivars tested were found positive for CarMV, indicating the widespread nature of CarMV in India. CarMV was separated from other carnation viruses by host-range studies and maintained on Saponaria vaccaria and Catharanthus roseus. The virus was purified from infected S. vaccaria leaves and characterized by SDS-PAGE. Morphological studies of CarMV were conducted by electron microscopy and immune electron microscopy. The electron micrograph showed isometric particles of about 30 nm in diameter, typical of CarMV. Complete coat. protein (CP) and movement protein (p7 and p9) genes of CarMV were amplified by RT-PCR with virus-specific primers. IC-RT-PCR was also used for sensitive detection of CarMV. Sequence alignment of the CP gene of Indian isolate of CarA/IV with other established isolates further confirmed the virus as CarMV. Though the amino acid sequence of CP was highly homologous, there are distinct differences. The Indian isolate is different from the already available classification of CarMV isolates. Isolates from the world belong to either the PK (P164 K331) or AN (A164N331) group, while the Indian isolate belongs to a new group PN (p164 N331). The p7 protein showed 85-98% amino acid similarity with the available protein sequences. The p9 protein showed 91-96% amino acid similarity with the available protein sequences of CarMV.