Both SSU rDNA and RNA polymerase II data recognise that root-knot nematodes arose from migratory Pratylenchidae, but probably not from one of the economically high-impact lesion nematodes

In 2000 Siddiqi formulated a hypothesis stating that root-knot nematodes (Meloidogyne spp.) constitute a branch arising from yet another important group of plant parasites, the migratory Pratylenchidae. This hypothesis was solely based on morphological characteristics. Ribosomal DNA (rDNA) sequence analysis supports this hypothesis in its broad sense, but the more precise question about the identity of a migratory Pratylenchidae representative being closest to the most basal Meloidogyne species could not be addressed due to a lack of backbone resolution (Holterman et al., 2009). Here we present an extended small subunit rDNA sequence analysis and a data set of partial RNA polymerase II sequences from Pratylenchidae and basal Meloidogynidae. Our data point at members of the genus Pratylenchus as being closest to the common ancestor of the root-knot nematodes, but it was not possible unequivocally to identify a candidate lesion nematode species. Pratylenchus is a species-rich genus (ca 70 valid species), and we suggest that the species closest to the most basal root-knot nematode should be sought outside of the group of relatively well-characterised, agronomically relevant, species