Population genetic analysis of potato virus X based on the CP gene sequence

To investigate the genetic variation and molecular evolution of potato virus X (PVX), 87 coat protein (CP) gene sequences were retrieved from GenBank and analyzed. Of the PVX isolates studied, one recombinant isolate (X3) was detected from South America population of the virus. The other isolates belonged to two lineages, Eurasia and America, with the significant F_ST value (0.60). Non-synonymous nucleotide diversity to synonymous nucleotide diversity (ω = dN/dS) was less than 1 indicating that the CP gene has been under negative selection or neutral evolution. Further analysis showed that all of the codons in both lineages were under negative selection pressure. No significant genetic differentiation was found between Chinese, Indian, Iranian, Japanese, and the UK populations whereas South America population was distinctly differentiated from other populations. Different evolutionary constraints found for the two lineages suggest that possible mutations and genetic drift were important evolutionary forces driving the genetic diversification of PVX population.