Characterisation and diagnosis of frangipani mosaic virus from India.

Frangipani mosaic virus (FrMV) is known to infect frangipani tree (Plumeria rubra f. acutifolia) in India but the virus has not been characterized at genomic level and diagnosis is not available. In the present study, an isolate of FrMV (FrMV-Ind-1) showing greenish mosaic and vein-banding symptoms in P. rubra f. acutifolia in New Delhi was characterized based on host reactions, serology and genome sequence. The virus isolate induced local symptoms on several new experimental host species: Capsicum annuum (chilli), Nicotiana benthamiana, Solanum lycopersicum and S. melongena. N. benthamiana could be used as an efficient propagation host as it developed systemic mottle mosaic symptoms all round the year. The genome of FrMV-Ind-1 was 6643 (JN555602) nucleotides long with genome organization similar to tobamoviruses. The Indian isolate of FrMV shared a very close genome sequence identity (98.3 %) with the lone isolate of FrMV-P from Australia. FrMV-Ind-1 together with FrMV-P formed a new phylogenetic group i.e. Apocynaceae-infecting tobamovirus. The polyclonal antiserum generated through the purified virus preparation was successfully utilized to detect the virus in field samples of frangipani by ELISA. Of the eight different tobamoviruses tested, FrMV-Ind-1 shared distant serological relationships with only cucumber green mottle mosaic virus, tobacco mosaic virus, bell pepper mottle virus and kyuri green mottle mosaic virus. RT-PCR based on coat protein gene primer successfully detected the virus in frangipani plants. This study is the first comprehensive description of FrMV occurring in India.