Genome analysis and characterization of a tobacco mosaic virus isolate infecting balsam (Impatiens balsamina)

The complete RNA genomic sequence of a tobacco mosaic virus isolate infecting Impatiens balsamina, designated as TMV-IM, has been determined. The genomic sequence and the predicted gene products of TMV-IM were similar to those of other members of the genus Tobamovirus. The CP ORF of TMV-IM showed sequence identities of 95.0–99.5% with the corresponding ORFs of other TMV strains. Full-length cDNA of TMV-IM was amplified by RT-PCR with a 5′-end primer harboring a T7 promoter sequence and a 3′-end TMV-specific primer. Subsequently, the full-length cDNA was cloned into plasmid vectors. Capped transcripts synthesized from the cDNA clone were highly infectious and caused characteristic symptoms in balsam plants, similar to wild-type TMV-IM and TMV-U1. These results provide definitive evidence for the natural occurrence of TMV in balsam.