En los últimos meses la misma idea ha resurgido en la literatura de la identificación molecular: "multi-locus barcode". A partir de la posición de usar un solo marcador molecular (código de barras del DNA), cada vez surgen mas ejemplos de lo complicado que es identificar monotéticamente. Aquí presento dos ejemplos recientes con el mismo mensaje: para identificar se necesitan varios marcadores moleculares.
Sin duda un gran redescubrimiento (230 años después).
"How Many Loci Does it Take to DNA Barcode a Crocus?
Ole Seberg*, Gitte Petersen
Laboratory of Molecular Systematics, Natural History Museum of Denmark, Copenhagen, Denmark
Source: PLoS ONE 4(2): e4598. doi:10.1371/journal.pone.0004598. February 2009
DNA barcoding promises to revolutionize the way taxonomists work, facilitating species identification by using small, standardized portions of the genome as substitutes for morphology. The concept has gained considerable momentum in many animal groups, but the higher plant world has been largely recalcitrant to the effort. In plants, efforts are concentrated on various regions of the plastid genome, but no agreement exists as to what kinds of regions are ideal, though most researchers agree that more than one region is necessary. One reason for this discrepancy is differences in the tests that are used to evaluate the performance of the proposed regions. Most tests have been made in a floristic setting, where the genetic distance and therefore the level of variation of the regions between taxa is large, or in a limited set of congeneric species.
The time is ripe for selecting barcode regions in plants, and for prudent examination of their utility. Thus, there is no reason for the plant community to hold back the barcoding effort by continued search for the Holy Grail. We must acknowledge that an emerging system will be far from perfect, fraught with problems and work best in a floristic setting."
"Selection of candidate coding DNA barcoding regions for use on land plants"
Authors: FORD, CAROLINE S.1; AYRES, KAREN L.2; TOOMEY, NICOLA3; HAIDER, NADIA4; VAN ALPHEN STAHL, JONATHAN5; KELLY, LAURA J.5; WIKSTRÖM, NIKLAS6; HOLLINGSWORTH, PETER M.7; DUFF, R. JOEL8; HOOT, SARAH B.9; COWAN, ROBYN S.5; CHASE, MARK W.5; WILKINSON, MIKE J.1
Source: Botanical Journal of the Linnean Society, Volume 159, Number 1, January 2009 , pp. 1-11(11)
An in silico screen of 41 of the 81 coding regions of the Nicotiana plastid genome generated a shortlist of 12 candidates as DNA barcoding loci for land plants. These loci were evaluated for amplification and sequence variation against a reference set of 98 land plant taxa. The deployment of multiple primers and a modified multiplexed tandem polymerase chain reaction yielded 85-94% amplification across taxa, and mean sequence differences between sister taxa of 6.1 from 156 bases of accD to 22 from 493 bases of matK. We conclude that loci should be combined for effective diagnosis, and recommend further investigation of the following six loci: matK, rpoB, rpoC1, ndhJ, ycf5 and accD.
© 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159, 1-11.
Keywords: genetic barcodes; matK; MT-PCR; multi-locus barcode; plant identification; plastid genes