DNA Barcoding for Taxonomic Resolution in Lamiaceae: Evaluating rbcL, matK, and trnH-psbA Markers for Species Identification

Abstract Lamiaceae family presents an example of the taxonomic complexities that challenge traditional identification methods. This study aimed to assay the effectiveness of three DNA barcoding markers (rbcL, matK, and trnH-psbA) for species identification within the genera Thymus, Mentha, and Salvia collected from various Egyptian locations. Results obtained indicated that rbcL showed a 100% amplification and sequencing efficiency across all genera nevertheless, it showed limited species resolution, with a genetic distance between Thymus and Mentha that reached 0.0154. On the other hand, matK and trnH-psbA showed superior species discrimination but lower amplification efficiency, especially for Salvia where it recorded a low of 12.5%. Interestingly, trnH-psbA marker showed the highest interspecific variability with 172 parsimony informative sites. Phylogenetic analysis using Neighbor-Joining trees supported distinct clades for each genus, with matK and trnH-psbA markers providing better resolution. Our study showed that matK and trnH-psbA are more effective for discriminating closely related species of Lamiaceae family. The incorporation of these markers increases the accuracy of taxonomic identification, and their application promotes conservation and ensures quality supply of Lamiaceae species of medicinal and commercial importance. The current study emphasizes the need for multi-locus DNA barcoding for biodiversity studies and its application in conservation of genetic resources as key aspects of Egypt's diverse flora.