Nucleotide sequence analysis of the ORF0 region of Potato leafroll virus isolates from Tunisia.

Potato leafroll virus (PLRV) isolates from potato plants from different regions of Tunisia were investigated for the ORF0 variable region of genomic RNA using PCR, nucleotide sequencing and sequence analysis. Based on the ORF0 variable region nucleotide sequence, individual Tunisian isolates were more homologous as a group compared to the isolates originating from other parts of the world. There was no correlation between bioclimatic origin of the isolates and their ORF0 sequence. Alignment of the deduced amino acid sequences showed that the P0 protein was not much conserved. Unexpectedly, Tunisian isolates were found to be most homologous to Peruvian ones both at nucleotide and amino acid level. A phylogenetic tree, based on the P0 amino acid sequence, showed that all the PLRV isolates were located in two major clusters regardless of their geographic origin. In the second cluster, three sub-clusters could be distinguished. These results provide valuable information for molecular characterization of the PLRV isolates occurring in Tunisia.