Phylogenetic Relationships of Globodera millefolii, G. artemisiae, and Cactodera salina Based on ITS Region of Ribosomal DNA.

Globodera millefolii and G. artemisiae are interesting because their type localities (Estonia and Russia, respectively) are geographically distant from those of the potato cyst nematodes and other Globodera species that seem to have originated in the Western world, and because the type host for each is a member of Compositae rather than Solanaceae. Sequence data for ITS1, ITS2, and 5.8S ribosomal DNA (ITS rDNA) for G. millefolii and G. artemisiae were nearly identical to sequence data for Cactodera salina from the rhizosphere of the estuary plant Salicornia bigelovii in Sonora, Mexico. The ITS rDNA sequences of these three species were all about 94% similar to those of two other Cactodera species for which ITS rDNA data were obtained. Phylogenetic analysis indicated that, based on the ITS rDNA data, G. millefolii and G. artemisiae are more closely related phylogenetically to the Cactodera species than to other nominal Globodera species. The molecular data further suggest that the genus Cactodera may comprise two or more morphologically similar but separate groups.