Assessment For Universal Plant DNA Barcodes Based On Species Of Rutaceae And Araceae Family

Objective:To find a universal DNA barcode sequence for plant species comparing with the candidate plant barcode sequences.Methods:490 samples of 223 species from 98 genus of the family Araceae and 300 samples of 192 species from 72 genera of the family Rutaceae were tested for identification efficiencies of some hot regains as the plant barcodes. To evaluate each barcode's utility for species authentication, PCR amplification efficiency, genetic divergence and barcoding gaps were assessed. After obtaining the desired results, we tested the identification efficiency of matK and rbcL in more than 27,000 samples.Results:matK sequence performed best in the all regions in the family Araceae.Then we extended to the whole vascular plants and found that the identification rate of matK was 70.1% in all 15765 samples. While 70.2% genus had an identification rate no less than 70% in all 1674 observed genus (genus containing no less than two species), and 12.7% genus has an identification rate less than 40%.As for rbcL, the identification rate is 61.6% in whole 11257 samples, while 56.4% genus had an identification rate no less than 70% in all 1619 observed genus (genus containing no less than two species) and 21.6% genus has an identification rate less than 40%. Because of the defect of matK and rbcL sequence, we continued to select barcode sequences using the barcode samples in the family Rutaceae. We found that the ITS2 locus had the highest identification efficiency among all tested regions. In a previous study, we found that ITS2 was able to discriminate a wide range of plant taxa, and here we confirmed that ITS2 was also able to discriminate a number of closely related species.Therefore, we propose that ITS2 is a promising candidate barcode for plant species identification.Conclusion:Compared to CO1 which was suitable to study DNA barcoding in animals, there is no single sequence suitable for identification of species throughout the plant kingdom. Based on our results and previous studies, we recommend the 3-locus combination of ITS2+matK+rbcL as the plant barcode. This core 3-locus barcode will provide a universal framework for the routine use of DNA sequence data to identify specimens and contribute toward the discovery of overlooked species of land plants.