The nucleotide sequence of shallot yellow stripe virus from onion(SYSV-O)in Shaanxi Province of China was described.It was 10427 nucleotides(nt)in length excluding the poly(A)tail and was predicted to encode a polyprotein of 3340 amino acids(aa)with a calculated molecular weight of 379.7kD.SYSV was most closely related to onion yellow dwarf virus(OYDV)and resembled it in having a much larger P3 protein than other species in the genus.SYSV-O shared 93.2% nt identity to the published sequence of a welsh onion isolate of SYSV(SYSV-ZQ2).The two isolates differed in NIb-CP cleavage site,that of SYSV-O was Q/V but Q/A in SYSV-ZQ2.Nucleotide identity of coat protein genes amongst all SYSV sequences ranged from 87.3%-84.1%.Phylogenetic tree analysis based on the 3’-terminal nucleotide sequences of SYSV isolates confirmed the existence of four distinct groups that were partially related to geographical origin and host plant species.
