Nearly 20 Years of Genetic Diversity and Evolution of Porcine Circovirus-like Virus P1 from China.

Porcine circovirus-like virus P1 can infect many kinds of animals and mainly causes postweaning multisystemic wasting syndrome. In China, the genetic diversity, variation, and evolutionary processes of this virus have not been described yet. To improve our knowledge of its genetic diversity, evolution, and gene flow, we performed a bioinformatics analysis using the available nucleotide sequences of the P1 virus; among them, 12 nucleotide sequences were from ten pig farms in Jiangsu Province in this epidemiological survey, and 84 sequences were downloaded from GenBank. The P1 sequences showed a rich composition of AT nucleotides. Analyses of the complete genomic sequences were polymorphic and revealed high haplotype (gene) diversity and nucleotide diversity. A phylogenetic analysis based on the NJ method showed that all P1 virus sequences formed two distinct groups: A and B. High genetic differentiation was observed between strains from groups A and B. The codon usage pattern of P1 was affected by dinucleotide compositions. Dinucleotide UU/CC was overrepresented, and dinucleotide CG was underrepresented. The mean evolutionary rate of the P1 virus was estimated to be 3.64 × 10 nucleotide substitutions per site per year (subs/site/year). The neutrality tests showed negative values. The purifying selection and recombination events may play a major driving role in generating the genetic diversity of the P1 population. The information from this research may be helpful to obtain new insights into the evolution of P1.