1.4.3 Molecular Authentication: DNA Barcoding

DNA barcoding provides a genotype-level authentication method that is largely immune to the morphological variability, processing damage, and adulteration...

DNA barcoding provides a genotype-level authentication method that is largely immune to the morphological variability, processing damage, and adulteration that can defeat macroscopic and microscopic methods. The technique targets short, standardised gene regions — most commonly the chloroplast genes rbcL (the large subunit of Rubisco) and matK, together with the nuclear internal transcribed spacer region ITS2 — that are sufficiently conserved to amplify reliably across the plant kingdom while remaining sufficiently variable to discriminate between closely related species. The standard workflow extracts genomic DNA (commonly by the CTAB method) from fresh or dried plant tissue, amplifies the target region by polymerase chain reaction, sequences the amplicon by Sanger sequencing, and compares the resulting sequence against curated reference databases such as NCBI GenBank or the Barcode of Life Data System (BOLD), with a sequence similarity exceeding approximately 97% conventionally taken as confirmatory of species identity. DNA barcoding's principal strength is its ability to detect adulteration and species substitution even in processed, dried, or powdered material where morphological and histological features have been destroyed.