title: DNA barcoding of the Lemnaceae, a family of aquatic monocots.
abstract: BACKGROUND
  Members of the aquatic monocot family Lemnaceae (commonly called duckweeds) represent the smallest and fastest growing flowering plants. Their highly reduced morphology and infrequent flowering result in a dearth of characters for distinguishing between the nearly 38 species that exhibit these tiny, closely-related and often morphologically similar features within the same family of plants.
  
  
  RESULTS
  We developed a simple and rapid DNA-based molecular identification system for the Lemnaceae based on sequence polymorphisms. We compared the barcoding potential of the seven plastid-markers proposed by the CBOL (Consortium for the Barcode of Life) plant-working group to discriminate species within the land plants in 97 accessions representing 31 species from the family of Lemnaceae. A Lemnaceae-specific set of PCR and sequencing primers were designed for four plastid coding genes (rpoB, rpoC1, rbcL and matK) and three noncoding spacers (atpF-atpH, psbK-psbI and trnH-psbA) based on the Lemna minor chloroplast genome sequence. We assessed the ease of amplification and sequencing for these markers, examined the extent of the barcoding gap between intra- and inter-specific variation by pairwise distances, evaluated successful identifications based on direct sequence comparison of the "best close match" and the construction of a phylogenetic tree.
  
  
  CONCLUSIONS
  Based on its reliable amplification, straightforward sequence alignment, and rates of DNA variation between species and within species, we propose that the atpF-atpH noncoding spacer could serve as a universal DNA barcoding marker for species-level identification of duckweeds.
authors.affiliation: Waksman Institute of Microbiology, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ 08854, USA.
authors.forename: Wenqin
authors.initials: W
authors.lastname: Wang
authors.forename: Yongrui
authors.initials: Y
authors.lastname: Wu
authors.forename: Yiheng
authors.initials: Y
authors.lastname: Yan
authors.forename: Marina
authors.initials: M
authors.lastname: Ermakova
authors.forename: Randall
authors.initials: R
authors.lastname: Kerstetter
authors.forename: Joachim
authors.initials: J
authors.lastname: Messing
mesh_terms: D058893:DNA Barcoding, Taxonomic / Q000379:methods*; D018742:DNA, Chloroplast / Q000235:genetics; D021901:DNA, Intergenic / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D005819:Genetic Markers; D019684:Magnoliopsida / Q000145:classification* / Q000235:genetics*; D010802:Phylogeny
chemical_list: D018742:DNA, Chloroplast; D021901:DNA, Intergenic; D018744:DNA, Plant; D005819:Genetic Markers