Data from: Discriminating plants using the DNA barcode rbcLb: an appraisal based on a large data set

The ideal DNA barcode for plants remains to be discovered, and the
candidate barcode rbcL has been met with considerable skepticism since its
proposal. In fact, the variability within this gene has never been fully
explored across all plant groups from algae to flowering plants, and its
performance as a barcode has not been adequately tested. By analyzing all
of the rbcL sequences currently available in GenBank, we attempted to
determine how well a region of rbcL performs as a barcode in species
discrimination. We found that the rbcLb region was more variable than the
frequently used rbcLa region. Both universal and plant group-specific
primers were designed to amplify rbcLb, and the performance of rbcLa and
rbcLb was tested in several ways. Using BLAST, both regions successfully
identified all families and nearly all genera; however, the successful
species identification rates varied significantly among plant groups,
ranging from 24.58% to 85.50% for rbcLa and from 36.67% to 90.89% for
rbcLb. Successful species discrimination ranged from 5.19% to 96.33% for
rbcLa and from 22.09% to 98.43% for rbcLb in species-rich families and
from 0 to 88.73% for rbcLa and from 2.04% to 100% for rbcLb in
species-rich genera. Both regions performed better for lower plants than
for higher plants, though rbcLb performed significantly better than rbcLa
overall, particularly for angiosperms. Considering the applicability
across plants, easy and unambiguous alignment, high primer universality,
high sequence quality, and high species-discrimination power for lower
plants, we suggest rbcLb as a universal plant barcode.