Molecular Identification And Sequence Analyses For Several Viruses Infecting Horticultural Plants

In this study, samples of three different horticultural species (Hibiscus rosa-sinensis linn., Lucuma nervosa, and Wisteria sinensis) exhibiting typical viral symptoms were subjected to biological, serological and molecular techniques for detection and identification of plant viruses inviloved. According to the results, it could definitely conclude that, samples of Hibiscus rosa-sinensis from South China was infected by Tobacco mosaic virus (TMV); in egg fruit (Lucuma nervosa A. DC), another strain of TMV was also detected; Wisteria vein mosaic virus (WVMV) was readily detected in samples from Beijing, Tianjin, and Shandong, thus providing the evidence for frequent occurrence of this virus in China.Complete nucleotides of Tomato mosaic virus isolated from Hibiscus rosa-sinensis in Henan Province (ToMV-hib) was cloned and sequenced. Subsequent sequence analyses were extensively performed with bioinformatic tools. The complete genomic sequence of ToMV (6,383 nucleotides) was obtained through RT-PCR, cloning and sequecing, which is the first ToMV isolated from Hibiscus ornamenatals. It demonstrated that ToMV-hib consisted of 71 and 206 nudeotides at the 5' and 3' non-translated regions respectively and it contains four opening reading frames (ORF), encoding four proteins essential for viral replication, cell-to-cell movement and particle assembly.The deduced amino acids were 125.67 kD, 182.97 kD, 28.94 kD, and 17.59 kD respectively in size. These observed properties agreed consistently with other known tobamoviruses.It is well known that host ranges for tobamoviruses are very wide, with a spedes number exceeding 200; yet most of them fall into non-woody plants such as brassicas, cucurbits, legumes, and solanaceous plants. From our results, we suggested that amino acid variations in RNA-dependent RNA polymerase and nucleotide variations in 5' non-translated region of ToMV-hib genome might be responsible for the host switch from herbaceous to woody plants. However, further experimental evidences are needed to support this assumation which is essentially and merely based on bioinformatics implications.