Identification Of A Wild Tomato Mosaic Virus Isolate(WTMV-XC-1) Infecting Nicotiana Tabacum In China

Wild tomato mosaic virus (WTMV), a member of the genus Potyvirus, has been reported inLaichau of Vietnam, Kanchanaburi of Thailand, Hainan and Guangdong of China since2008. Avirus isolate, which was detected from Nicotiana tabacum showing severe mosaic symptoms inXichang of Sichuan, was proved to be a member of WTMV and was named WTMV-XC-1in thisstudy.Microscopic observation, inoculating experiment, and bioinformatics methods were taken tostudy WTMV-XC-1. It had flexuous filamentous particles about740-760nm in length and13nmin diameter by electron microscopy. N. tabacum NC89inoculated XC-1developed vein clearing5days post inoculation（dpi）and mosaic symptoms8-14dpi, while Lycopersicon esculentuminoculated XC-1developed yellowing10dpi and leaf necrosis along vein17dpi.The completegenomic sequence of XC-1was determined to be9659nucleotides, excluding3’ terminal poly(A)tail. Bioinformatics analysis showed that XC-1had genome typical of genus Potyvirus, encodinga large polyprotein of3075amino acids. Putative proteolytic cleavage sites and many wellcharacterized functional motifs were identified by sequence comparison to those of knownpotyviruses. Phylogenetic analysis was constructed based on the nucleotide sequence of theentire genomes. Neighbor-joining tree showed that, XC1clustered within the ChiVMV subgroup,and was most closely related to WTMV Laichau isoalte. Multiple alignments of the completenucleotide revealed that XC-1shared the highest level of nucleotide sequence identity (76.48%)with WTMV Laichau isolate and an identity of94.34%with Guangdong isolate based on the CPgene sequence.A pair of specific primers was designed based on the conserved CP gene of WTMV. ASYBR GreenⅠreal-time reverse transcription-polymerase chain reaction (rRT-PCR) assay wasdeveloped for rapid detection and quantitation of WTMV in this study. The result showed thatthis assay of high sensitivity and specificity and good reproducibility could detect WTMV in N.tabacum and Myzus persicae Sulzer.The complete genomic sequence of WTMV-XC-1was determined in this study, and thegenomic data may serve as a basis for future investigations on the gene diversity of WTMV. TheSYBR GreenⅠrRT-PCR assay developed here will be helpful in epidemiological studies of WTMV and in applied studies aiming to control WTMV.