| Potato virus Y (PVY) is one of the most important pathogens of potato and tobacco in China. Genetic variability of PVY isolates infecting potato have been characterized, but little information about genetic diversity and characterize of PVY isolates infecting tobacco crops. There is no related report of this pathogen in Guangxi Province. In this study, the serologic and genome complete sequence of four isolates infecting tobacco crops in Guangxi was determined. The isolates of GX-1, GX-2 and GX-3 all induced tobacco veinal necrosis and have antigen and antibody reaction with PVYO+C, while the isolate GX-4 induced tobacco mosaic and mottle have PVYO+C serotype too. Excluding the poly(A) tail, the GX-1 GX-2 GX-4 and GX-3 viral genome consists of 9699,9702,9702 and 9703 nucleotides in length respectively. All of them encoded a polyproetin of 3061 amino acids, which was then cleaved into ten functional products by three virus-encoded proteases. The identity of four isolates GX-1, GX-2, GX-3 and GX-4 with other 20 PVY isolates were 89.8%～98.6%,88.4%～99.7% and 89.3%～96.1%, respectively. The HC-Pro of isolates GX-1 GX-2 and GX-3 had three aminoacids D205, K400 and E419 which were previously reported as determinant keys of the tobacco necrotic response. The corresponded amino acid was R in the HC-Pro of GX-4. The isolates of GX-1, GX-2 and GX-3 were recombinants of PVYO and PVYN. The isolate GX-1 possessing four widely recombinant joints at P1, HC-Pro/P3,6K2/VPg and Nib/CP regions, which is the first determined in China. However, the recombinant events in GX-2 and GX-3 were similar to that in PVYNTN-HN2 previously reported from Hunan province, which possessing three recombinant joints. A phylogenetic analysis of complete sequences showed that GX-1 was most closely related to Wilga156 (PVYN-Wi), SYR-Ⅱ-2-8, SYR-Ⅱ-DrH and SYR-Ⅱ-Bel PVYNTN-NW) isolates. Both GX-2 and GX-3 were most closely related to Guiding-3 and HN2 (PVYNTN) isolates. However, the genotype of GX-4 was clustered to PVYN group. |
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