Mitochondrial Genome Assembly and Comparative Analysis of Chionanthus Retusus (Oleaceae)

<b>Background/Objectives</b>: <i>Chionanthus retusus</i> Lindl. & Paxton is an ornamental tree species native to North China. Research on the mitochondrial genome can elucidate the evolution and biological characteristics of <i>C. retusus</i> and better protect this important species. <b>Methods and Results</b>: This work aimed to clarify the evolutionary and phylogenetic links by sequencing, assembling, annotating, and analyzing the entire mitochondrial genome of <i>C. retusus</i>. The single-loop structure that made up the mitochondrial genome had a total length of 657,640 bp and a GC content of 44.52%. In total, 37 unique protein-coding genes, 20 tRNA genes, and 3 rRNA genes were identified. Numerous repeat sequences and migrating fragments of chloroplast sequences were found. Using the mitochondrial protein-coding genes to construct evolutionary trees, it was found that the closest relative of <i>C. retusus</i> is <i>C. rupicola</i> (Lingelsh.) Kiew. <b>Conclusions</b>: This research represents the first comprehensive set of data on the mitochondrial genome of an ancient (>500 yr) <i>C. retusus</i> specimen. In addition to elucidating the biological characteristics of <i>C. retusus</i>. The findings contribute to the Oleaceae mitochondrial genome database and offer valuable insights for future studies in molecular breeding, evolutionary biology, and genetic diversity conservation.