Characterization of tobacco mosaic virus isolated from tomato in India

Tomato mosaic tobamovirus (ToMV) differs from the type strain of tobacco mo saic virus (TMV) in producing local lesions instead of systemic infection o n Nicotiana sylvestris. An isolate collected from Kolar district of Karnata ka which produced this differential host reaction was propagated in the gre enhouse on N. tabacum cp. Samsun and purified. The virus is a rigid rod sha ped particle with a coat protein of molecular weight 18 kDa and genomic RNA of size 6.3 kb. A cDNA library was constructed using a specific primer des igned based on the conserved nucleotide sequence at the 3' non coding regio n of tobamoviruses. The cDNA library was screened for recombinant Clones an d, the recombinant clone 82 with an insert of size 1.04 kb was sequenced in both directions. This sequence was compared with the genomic sequence of T MV and ToMV which showed 93.1 and 73.7 per cent identity, respectively. The sequence encompassed the 3' non coding region, the complete coat protein O RF and 467 nucleotides of the, movement protein. The deduced amino acid seq uence of the coat protein was compared with that of TMV and ToMV. This-sequ ence was nearly identical to TMV with nine amino acid changes whereas thirt y-two changes were observed with ToMV. This suggests that the virus under s tudy is a strain of TMV and therefore we have named it as tobacco mosaic vi rus tomato strain from Karnataka, India (TMV(Tom-K)).