Characterization and phylogenomic analysis of the complete chloroplast genome of Schwenckia americana (Schwenckioideae, Solanaceae)

Schwenckia americana L. (Schwenckioideae, Solanaceae) is a medicinal herb, but genomic resources are limited. To address this gap, we report the first complete chloroplast (cp) genome of S. americana , assembled de novo from Illumina sequencing data. The circular cp genome is 152,334 bp with a quadripartite structure consisting of a large single-copy (LSC) region (85,088 bp), a small single-copy (SSC) region (18,494 bp), and two inverted repeats regions (IRa and IRb) (24,376 bp each). A total of 112 unique genes were annotated, comprising 77 protein-coding genes, 30 tRNA genes, 4 rRNA genes, and one pseudogene ( infA ). Codon usage analysis revealed bias toward A- or T-ending codons. Leucine was encoded most frequently (10.7%), while cysteine was the least frequent (1.2%). We identified 55 simple sequence repeats (SSRs), the majority of which were A/T mononucleotide motifs. Phylogenomic analysis based on cp genomes of 35 Solanaceae species (with Ipomoea alba as the outgroup) robustly placed S. americana as an early-diverging lineage sister to Petunioideae, Nicotianoideae, and Solanoideae. These results provide chloroplast-scale evidence supporting the basal position of Schwenckioideae within the family. The cp genome of S. americana represents an important genomic resource for future comparative and evolutionary studies of Schwenckia and the Solanaceae.