Abstract:Typical tobacco bushy top disease was mainly caused by mixed infection of Tobacco bushy top virus (TBTV) and Tobacco vein distorting virus (TVDV). Coat protein (CP) encoded by TVDV could package the genome of TBTV and TVDV respectively, resulting in forming of virions and mediating the transmission by aphid. However, some disease samples in the field contain the TVDV in the absence of TBTV. In this study, cp genes of two types of TVDV (TVDV-MD isolate with the coexistence of TBTV and TVDV-BS isolate without the coexistence of TBTV), were cloned by RT-PCR and compared. The lengths of TVDV-MD and TVDV-BS cp genes are 618 nt and 621 nt, respectively. Moreover, nucleotide and amino acid identities of cp gene between TVDV-MD and TVDV-BS were 90.02 % and 89.81 %, suggesting that TVDV-MD and TVDV-BS CPs belong to different types. However, sequence identities of TVDV cp gene with the same length were 98.5 % -100%. In addition, phylogenetic analysis also showed that these two types of cp gene respectively belong to two groups with far distance. Although TVDV-MD CP and TVDV-BS CP have about 10% amino acid divergence, their structures predicted by SWISS-MODEL did not present remarkable difference with only slight alteration in minor elements and linker regions. Our results suggested that mutation on amino acid sequences rather than the change of structure of CP in TVDV-BS might cause the inability of packaging of TBTV and result in missing the TBTV during the transmission of tobacco bushy top disease.