Exploring the DNA barcoding potential of Nigerian arid-land Mimosoideae using a multigene tiered approach

The sub-family Mimosoideae comprises members of major economic importance. Many representatives of this group are difficult to identify solely using morphological features, hence the necessity to develop an efficient and accurate means to identify its members. In this study, the DNA barcode potential of different genetic loci in Mimosoideae was explored. Four genetic regions (ribosomal ITS and plastid rbcL, matK and trnL intron) were investigated to accurately identify its species. These regions were evaluated based on (i) PCR-amplification (ii) sequencing success, (iii) intra- and inter-specific divergence, (v) DNA barcoding gaps and (vi) identification efficiency. ITS region exhibited the highest amplification success rate whereas both rbcL and matK displayed the highest sequencing success rate. The six parameters used to characterize intra- versus interspecific divergence revealed that ITS exhibited the highest discrimination potential whereas rbcL was the least in performance. Using Wilcoxon signed rank tests, ITS and matK exhibited the highest inter-specific divergence between congeneric species whereas ITS and trnL displayed the highest intra-specific distance. ITS region exhibited a high barcoding gap of 2.00; ITS + matK, ITS + rbcL, ITS + matK + rbcL + trnL-F, a barcoding gap of 1.00, whereas other regions revealed no barcoding gap. Based on all analyzed parameters, ITS region proved superior in species discrimination with the most accurate identification potential, significantly higher than matK, rbcL or trnL intron. Our results propose ITS as an attractive barcode or as a locus complementary to other previously approved plant barcode regions. ITS region constitutes a promising DNA locus candidate to accurately identify members of the Mimosoideae.