Molecular Identification of the Causative Agents of Tobacco Bushy Top Disease in Zimbabwe

PurposeTo identify the components of the causative agents of tobacco bushy top disease in Zimbabwe.

MethodA tobacco bushy top diseased plant was collected from Zimbabwe, and molecular identification of the virus complex was conducted.

ResultsThe genomic nucleotide identities of TBTV-Zimbabwe with other umbraviruses were 47.8%-94.6%. TBTV-Zimbabwe had the highest identity of 94.6% with Ethiopian tobacco bushy top virus (ETBTV). TBTV-Zimbabwe had 56.9% identity with a Chinese isolate of tobacco bushy top virus (TBTV). Molecular phylogenetic analyses showed that TBTV-Zimbabwe was an isolate of ETBTV and it was distantly related to TBTV, which was a distinct virus species. The genomic nucleotide sequence identity between TBTV-Zimbabwe satellite RNA and ETBTV satellite RNA was 93.9%, and TBTV-Zimbabwesatellite RNA showed no homology with other sequences in the GenBank except ETBTV satellite RNA. Nucleotide sequence encoding partial coat protein of potato leafroll virus (PLRV) was determined in tobacco bushy top complex in Zimbabwe.

ConclusionThree viral components were identified in tobacco bushy top disease complex in Zimbabwe. Each of them was identical to the components of tobacco bushy top disease complex in Ethiopia at the virus species level. The causative agents of Zimbabwean and Chinese tobacco bushy top disease were not the same.