Identification of Genus Vigna using ITS2 and matK as a Two-Locus DNA Barcode

DNA barcoding is the use of short DNA sequences of the genome for large scale species identification. The Consortium for the Barcode of Life (CBOL) plant-working group recommended a 2-locus combination as the standard plant barcode. The evolutions of the chloroplast regions combined with nuclear gens are sufficiently rapid to allow discrimination between closely related species. We evaluated the efficacy of the proposed plant barcoding loci, matK, along with ITS2 for barcoding the Vigna species. To assess the discriminatory ability of barcoding loci for identifying the Vigna species, we sampled 52 of the taxonomically best known groups in the genus. Topologies of the phylogenetic trees based on ITS2 and matK analyses were similar but a few accessions were placed into distant phylogenetic groups. Neither ITS2 nor matK analyses were able to discriminate some closely related Vigna species. Thus, we used concatenated data to increase the resolving power of ITS2 and used matK as an additional tool for phylogenetic analysis in Vigna because characterization of the nucleotide sequences of the matK region was easier and more cost-effective than that of the ITS region.