The Complete Chloroplast Genome of Synotis solidaginea and Phylogenetic Analysis

Synotis is an important genus within the Asteraceae family. The genus comprises numerous species, many of which exhibit highly similar morphology, making identification using traditional taxonomic methods challenging. Therefore, developing a scientifically sound and effective identification method for Synotis plants is of significant importance. In this study, the complete chloroplast (cp) genome of Synotis solidaginea was sequenced using the Illumina HiSeq 4000 platform, analyzed, and compared with its closely related species. The results revealed that the complete chloroplast genome of S. solidaginea is 150,899 bp in length with a GC content of 37.47%. It exhibits the typical quadripartite structure, consisting of a large single-copy (LSC) region (83,338 bp), a small single-copy (SSC) region (17,885 bp), and two inverted repeat (IR) regions (each 24,838 bp). The genome encodes a total of 127 genes, including 83 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. Thirty-two simple sequence repeats (SSRs) were identified. Four highly variable regions (trnG-UCC, ndhC-trnV-UAC_2, trnY-GUA-trnE-UUC, and trnH-GUG-psbA) were identified as potential DNA barcodes for species identification. Phylogenetic analysis revealed that S. solidaginea is closely related to its congeneric species Synotis cavaleriei, Synotis erythropappa, Synotis duclouxii, and Synotis nagensium. This study provides a reference for the phylogenetic analysis of Synotis using chloroplast genomics, and offers data support for the hybrid breeding of S. solidaginea to cultivate desirable ornamental traits or stress resistance traits. Furthermore, chloroplast genome research can also assist researchers in gaining a deeper understanding of the species origin of S. solidaginea and contribute to the study of species conservation and utilization.