Variation analysis of two cucumber mosaic viruses and their associated satellite RNAs from sugar beet in China.

Two cucumber mosaic virus (CMV) isolates XJ1 and XJ2 were obtained from sugar beet showing yellow mosaic symptom in Shihezi, Xinjiang Uigur municipality of China. The coat protein gene of the two CMV isolates and their associated satellite RNAs were amplified by reverse transcriptase polymerase chain reaction (RT-PCR) and were cloned and sequenced. Comparison of CP gene sequences showed that XJ1 and XJ2 have the highest sequence identity with that of CMV-Danshen (97.8%) and CMV-SD (98.7%), respectively. Two types of satellite RNAs (XJs1 and XJs2) were found to be associated with the two CMV isolates consisting of 384 nucleotides and 336 nucleotides, respectively. Sequence comparisons revealed that XJs1 and XJs2 were most closely related to CS2-sat and CS1-sat, respectively, with 98.9% and 98.5% nucleotide sequence identity. Phylogenetic analysis of nucleotide sequence and deduced amino acid sequence of coat protein gene revealed that XJ1 and XJ2 belong to subgroup IB but there exist some variation between them. Parallel analyses of nucleotide sequence of XJsl and XJs2 suggested that these two satellite RNAs probably originated from China.