Abstract
Melilotus, an annual or biennial herb, belongs to the tribe Trifolieae (Leguminosae) and consists of 19 species. As an important green manure crop, diverse Melilotus species have different values as feed and medicine. To identify different Melilotus species, we examined the efficiency of five candidate regions as barcodes, including the internal transcribed spacer (ITS) and two chloroplast loci, rbcL and matK, and two non-coding loci, trnH-psbA and trnL-F. In total, 198 individuals from 98 accessions representing 18 Melilotus species were sequenced for these five potential barcodes. Based on inter-specific divergence, we analysed sequences and confirmed that each candidate barcode was able to identify some of the 18 species. The resolution of a single barcode and its combinations ranged from 33.33% to 88.89%. Analysis of pairwise distances showed that matK+rbcL+trnL-F+trnH-psbA+ITS (MRTPI) had the greatest value and rbcL the least. Barcode gap values and similarity value analyses confirmed these trends. The results indicated that an ITS region, successfully identifying 13 of 18 species, was the most appropriate single barcode and that the combination of all five potential barcodes identified 16 of the 18 species. We conclude that MRTPI is the most effective tool for Melilotus species identification. Taking full advantage of the barcode system, a clear taxonomic relationship can be applied to identify Melilotus species and enhance their practical production.
Highlights
Melilotus, an annual or biennial herb, belongs to the tribe Trifolieae (Leguminosae) and consists of 19 species mainly distributed in North Africa and Eurasia [1]
We thank the National Plant Germplasm System (NPGS, US) and National Gene Bank of Forage Germplasm (NGBFG, China) for providing experimental materials used in our study
We found that internal transcribed spacer (ITS) was to be the best candidate barcode among the five single loci (Fig 2)
Summary
Melilotus (sweet clover), an annual or biennial herb, belongs to the tribe Trifolieae (Leguminosae) and consists of 19 species mainly distributed in North Africa and Eurasia [1]. These species can endure extreme environmental conditions, such as high salinity, drought and cold [1, 2], and have important medicinal value [3]. Coumarin is an important plant secondary metabolism compound found in Melilotus [4] and possesses a several antitumor activities, both preventing the occurrence of cancer and potentially curing cancer [5]. Yanrong Wang and Jiyu Zhang decided to publish the manuscript
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