Discovery and Identification of Species Using COI DNA Barcoding.

DNA barcoding with a new cytochrome oxidase c subunit 1 primer set generated a 721 to 724 bp fragment used for the identification of 322 Meloidogyne specimens, including 205 new sequences combined with 117 from GenBank. A maximum likelihood analysis grouped the specimens into 19 well-supported clades and four single-specimen lineages. The "major" tropical apomictic species ( Meloidogyne arenaria , Meloidogyne incognita , Meloidogyne javanica ) were not discriminated by this barcode although some closely related species such as Meloidogyne konaensis were characterized by fixed diagnostic nucleotides. Species that were collected from multiple localities and strongly characterized as discrete lineages or species include Meloidogyne enterolobii , Meloidogyne partityla , Meloidogyne hapla , Meloidogyne graminicola , Meloidogyne naasi , Meloidogyne chitwoodi , and Meloidogyne fallax . Seven unnamed groups illustrate the limitations of DNA barcoding without the benefit of a well-populated reference library. The addition of these DNA sequences to GenBank and the Barcode of Life Database (BOLD) should stimulate and facilitate root-knot nematode identification and provide a first step in new species discovery.