DNA Barcoding of Medicinal Plants

Abstract

DNA barcoding is a useful technique for diversity analysis whereby a standardized region of DNA is used for the identification of a species or a taxonomic group of organisms. These standard regions used for identification are called the DNA barcode. These are small sequences of the entire genome. In plants, DNA barcoding has application in phylogenetic analysis, authentication, inter- and intraspecific diversity, classification into wild and cultivated genotypes, the study of phylogeographical patterns, and in the detection of adulteration. The barcode loci, i.e., the DNA regions used for the identification are able to discriminate the closely related species and identify new cryptic species as well. Depending on the taxon and complexity of the species, different barcode loci are used for the purpose. In animals, the universal DNA barcode, i.e., mitochondrial cytochrome c oxidase I (COI) gene is used for species discrimination. However, this gene cannot be used for plants due to its limited divergence. Thus, its use is limited only to some algae. Efforts are going on to find suitable universal barcode loci for plants. Since the last decades, matK, rbcL, trnH-psbA, ITS, trnL-F, 5S-rRNA, and 18S-rRNA candidate regions are being used as DNA barcodes in plants. The article provides an overview of the use of these candidate regions through different approaches which have gained importance due to the challenges in DNA barcoding of plants. The development of multilocus and tiered approaches along with the new frontier areas for application of this technique has been analyzed in detail.