Molecular identification and the complete nucleotide sequence of TYLCV isolate from Shanghai of China.

Tomato yellow leaf curl virus (TYLCV) belongs to the genus Begomovirus, family Geminiviridae. It is transmitted by the whitefly Bemisia tabaci. A pair of primers was designed according to the specific sequence of the TYLCV gene and used in the PCR detection of the virus in the infected tissues of tomato grown in the Shanghai area of China. DNA was extracted from leaves, fruits, seeds, and roots of infected tomato plants separately. The results showed that the target fragment of about 570 bp could be isolated from the leaves, fruits, roots of infected tomato plants, but not from the seeds. Thus, the PCR-based detection technology for the Shanghai TYLCV (TYLCV-Sh10) has been established. Primers were then designed based on the sequence of the 570 bp fragment to obtain the complete DNA-A sequence of TYLCV-Sh10 by genome walking. Sequencing results indicated that the DNA-A sequence of TYLCV-Sh10 contained 2781 nt that included six ORFs. BLAST results showed that DNA-A of TYLCV-Sh10 had low homology with the characterized TYLCV in China (TYLCCNV) except TYLCV-ZJ8 (TYLCV isolated from Zhejiang China). But it was most closely related to TYLCV-USA (99.28% sequence identity). TYLCV-Sh10, TYLCV-ZJ8, TYLCV-USA, TYLCV-Mex, and TYLCV-Eg formed an independent branch by pairwise comparison and phylogenetic analysis. All these results strongly suggested that Sh10 was an isolate of America or Africa TYLCV.