Chloroplast Genome Sequencing and Comparative Analysis of Six Medicinal Plants of .

The genus boasts abundant germplasm resources and comprises numerous species. Among these, medicinal plants of this genus, which have a long history, have garnered attention of scholars. This study sequenced and analyzed the chloroplast genomes of six species of medicinal plants (, , , , , and , respectively) to explore their interspecific relationships. The sequence length (154, 578-155, 807 bp) and genome structure were conserved among the six species, with a typical tetrad structure. Among the 127-131 genes contained in the genomes, 84-85 are protein-coding genes, 37-38 are transfer RNA genes, and 6-8 are ribosomal RNA genes. The genomes contained 64-76 simple sequence repeats (SSRs) and 36-62 long repetitive sequences. Codon bias patterns tended to use codons ending in A/T. In 30 types of codons with RSCU > 1, 93.3% ended in A/T of the six species. Twenty-one highly variable plastid regions were identified in the chloroplast genomes of the six medicinal plants. Furthermore, a phylogenetic analysis encompassing these and 53 other chloroplast genomes of species revealed that , , and clustered together on one clade, whereas and formed separate clades. Notably, emerged as a standalone clade, and our phylogenetic tree reinforces the classification of as forming a monophyly. This study provides a novel basis for intragenus taxonomy and DNA barcoding molecular identification within the genus medicinal plants.