| DNA of a total of 21 species, 2 subspecies, and a non-nominal "species" of plant parasitic nematodes from five families were sequenced in two different DNA regions. The nuclear rDNA region (780 bp) and mitochondrial COII gene (165 bp) from Heterodera glycines, H. carotae, H. schachtii; mitochondrial sequences from Meloidogyne hapla (400 bp) and M. chitwoodi (467 bp) were compared to estimate intraspecific nucleotide diversity. The nucleotide distances of the three H. glycines isolates were 0.1-0.3% for the rDNA region and 1.8-3.0% for the mitochondrial COII gene. The nucleotide distances of the five H. carotae isolates were 0.3-1.9% for the rDNA region and 0.0-4.9% for the mitochondrial COII gene. The Italian isolate was the most divergent from the three Michigan and Northern Ireland isolates with nucleotide distances 4.9% and 3.8%, respectively. Among Michigan isolates the identical 165 bp of the mitochondrial COII gene suggested the recent introduction of these populations into the three Michigan counties. The nucleotide distances of the three H. schachtii isolates were 0.3-0.7% for the rDNA region and 1.2-6.7% for the mitochondrial COII gene. The interspecific nucleotide distance in ITS1 region across 12 Heterodera species was 3.0-32.8% and among 3 Globodera species was 0.2-5.6%.; The most striking result from a phylogenetic analysis of 175 bp of the 18s rRNA gene was the non-monophyletic relationship of Heteroderinae and Meloidogyninae. Meloidogyninae formed a clade together with four other Tylenchida families (Belonolaimidae, Criconematidae, Hoplolaimidae, and Pratylenchidae) to the exclusion of Heteroderinae. Within Heteroderinae all 12 Heterodera species appeared monophyletic. H. carotae, H. cruciferae, and H. goettingiana formed Clade I as a sister group to the rest of the clades with bootstrap and branch support values 99% and 4 in PAUP, respectively. Within Globodera, G. pallida was a sister group to the rest of the species. |
