Complete chloroplast genomes of 13 species of the Impatiens genus for genomic features and phylogenetic relationships studies

Impatiens spp. are well-known ornamental and medicinal plants that are widely distributed in the highlands and mountains of southwestern China. This area is one of the hotspots for the distribution of Impatiens species, with typical karst landforms and abundant wild resources. Many of these species are endemic to a narrow distribution area, but their classification and relationships are relatively unclear because of insufficient field investigations, diverse morphological characteristics and lack of molecular information. In this study, chloroplast genome analysis of 13 species (including 2 synonyms) in karst habitats was conducted to study their characteristics and phylogenetic relationships. The results revealed that these chloroplast genomes all had double-stranded tetrad structures ranging in length from 151,284 bp to 152,421 bp, including a total of 113 genes, including 80 protein-coding genes, 29 transfer RNAs, and 4 ribosomal RNAs. SSRs mainly consist of A/T repeats and AT/AT repeats, while INEs mainly consist of positive repeats and palindromic repeats. The frequency of codon usage was essentially the same, with a total of 31 high-frequency codons detected, the vast majority ending in A/U. Five mutation hotspots were detected: rps16-trnQ-UUG, ndhF, ccsA-ndhD, ycf1, and trnN-GUU, among which ycf1 had the highest Pi value and the greatest potential as a DNA barcode marker. Our phylogenetic tree shows that all 13 species belong to Section Impatiens. And supported the classification of I. reptans and I. rhombifolia should as synonyms (BS = 100/PP = 1.00). This study comprehensively analyzed the cp genomes of different taxa, sheds light on the taxonomic intricacies of Impatiens species, provide valuable information into its phylogenetic and taxonomy.