Codon Usage Bias of Chloroplast Genome in Astragalus Species

To clarify the codon characteristics and evolutionary pressure of Astragalus chloroplast genomes, the coding DNA sequences of 36 Astragalus chloroplast genomes were used to analyze their codon base composition, codon adaptation index, codon usage bias, codon bias index, optimal codon usage frequency, effective codon number, and correlations. The means ± SD were used to evaluate the genetic diversity of 53 protein-coding genes. The results showed that the codons of Astragalus chloroplast genomes tended to end with A/U. Additionally, natural selection was the main factor affecting codon usage, and mutation pressure affected to some extent. The results of this study provide reference for the evolution and phylogeny of Astragalus species.