# Determination of the Phylogenetic Relationship of Dendrobium linawianum (Orchidaceae) Based on Comparative Analysis of Complete Chloroplast Genomes

## TL;DR

This study determines the evolutionary relationship of the endangered orchid Dendrobium linawianum using its complete chloroplast genome.

## Contribution

The paper provides the first complete chloroplast genome of Dendrobium linawianum and resolves its phylogenetic position within the genus.

## Key findings

- The complete chloroplast genome of D. linawianum is 150,497 bp and contains 119 genes.
- Phylogenetic analysis shows D. linawianum is closely related to D. hercoglossum, D. thyrsiflorum, and D. moniliforme.
- Chloroplast genomes effectively resolve phylogenetic relationships among 35 Dendrobium species.

## Abstract

Dendrobium is an orchid genus with high economic and ecological importance, but its taxonomy based on morphology remains controversial. Dendrobium linawianum, a critically endangered species with both ornamental and medicinal value, represents a key taxon within this genus. However, its phylogenetic relationship has long been unplaced due to similar morphological traits. Despite its conservation and taxonomic importance, its complete chloroplast genome has not been previously characterized. Here, we newly sequenced and assembled the complete chloroplast genome of D. linawianum. The 150,497 bp genome exhibits a typical quadripartite structure, encoding 119 genes. A total of 161 simple sequence repeats (SSRs) were identified, predominantly mononucleotide and dinucleotide motifs. Condon usage analysis revealed leucine as the most abundant amino acid. Phylogenetic analysis based on complete chloroplast genome sequences strongly supported the close relationship of D. linawianum with D. hercoglossum, D. thyrsiflorum, and D. moniliforme, resolving its taxonomic position within the genus. The complete chloroplast genomes successfully resolved the phylogenetic relationships among 35 Dendrobium species, demonstrating their efficacy as powerful molecular markers for resolving taxonomic ambiguities within this morphologically complex genus. Our findings provide a genomic foundation for precise species identification and molecular breeding of D. linawianum, and enhance understanding of phylogenetic relationships in this taxonomically challenging group.