Plectranthus is a genus of the Lamiaceae family that includes many species of medicinal and agricultural importance. However, this genus has been the subject of taxonomic debate and contains species that are difficult to distinguish. The present study focused on six Plectranthus species commonly found in Saudi Arabia: P. arabicus, P. tenuiflorus, P. barbatus, P. pseudomarrubioides, P. asirensis, and P. hijazensis. P. hijazensis is endemic to Saudi Arabia. The capacities of five different plastid DNA barcodes (matK, rbcL, trnH-psbA, and ITS1 and ITS2 regions of the nrDNA gene) to identify and distinguish between Plectranthus species were evaluated. The following analytical methods were used to evaluate the efficiencies of the selected markers: BLAST, inter- and intraspecific distance, barcode gap, secondary structure of ITS2, and maximum likelihood (ML) phylogenetic trees. The results demonstrated that the nuclear ITS2 region can be successfully amplified and sequenced (100%), leading to a strong ability to discriminate between species and a clear barcode gap. Furthermore, there were significant differences in the ITS2 secondary structure among Plectranthus spp. Samples of Plectranthus formed monophyletic groups according to species in the ML tree, with high supported values. Our results establish that all Plectranthus species in Saudi Arabia can be classified into two groups within the Coleus clade. To our knowledge, this is the first time that local and endemic Plectranthus spp. have been identified and compared with Plectranthus samples of different geographical origins. Our results confirm the diversity of Plectranthus species growing naturally in southwestern Saudi Arabia. In addition, P. hijazensis, which is endemic to Saudi Arabia, was determined to be genetically distinct from other Plectranthus species and should, therefore, be the focus of future research, in addition to the preservation of the natural environment of these species.

Plectranthus是唇形科的一属，包括许多具有医学和农业意义的物种。但是，该属一直是分类学辩论的主题，并且包含难以区分的物种。本研究主要集中在六大之左手在沙特阿拉伯常见种类：P. arabicus，P. tenuiflorus，P.石竹，P. pseudomarrubioides，P. asirensis，和P. hijazensis。P. hijazensis是沙特阿拉伯特有的。五个不同质体DNA条形码（matK，rbcL，trnH-psbA以及ITS1和ITS2）的容量鉴定和区分了侧柏物种的nrDNA基因区域）。以下分析方法用于评估所选标记的效率：BLAST，种间和种内距离，条形码间隙，ITS2的二级结构以及最大似然（ML）系统树。结果表明，核ITS2区域可以成功扩增和测序（100％），从而具有很强的区分物种和清除条形码间隙的能力。此外，P香属植物之间的ITS2二级结构存在显着差异。样品的左手根据ML树中的物种形成单系群，具有较高的支持值。我们的结果表明，在锦紫苏分支中，沙特阿拉伯的所有鸢尾科物种都可以分为两类。据我们所知，这是本地和地方性P香属植物的首次。已鉴定并与不同地理来源的凤尾兰花样品进行了比较。我们的结果证实了在西南沙特阿拉伯自然生长的凤尾木物种的多样性。此外，沙特阿拉伯特有的hijazensis P.被确定与其他Plectranthus在遗传上是不同的 物种，因此，除了保护这些物种的自然环境外，应该成为未来研究的重点。