Plant-parasitic nematodes were found in 4 of the 12 clades of phylum Nematoda.These nematodes in different clades may have originated independently from their free-living fungi vorous ancestors.However, the exact evolutionary process of these parasites is unclear.Here, we sequenced the genome sequence of a migratory plant nematode, D.destructor.We performed comparative genomics among the free-living nematode, C.elegans and all the plant nematodes with genome sequences available.We founded that, compared to C.elegans, the core developmental control processes underwent heavily reduced, though most signal transduction pathways were conserved.We also found D.destructor contained more homologies of the key genes in the above processes than the other plant nematodes.We suggest that Ditylenchus spp.may be an intermediate evolutionary history stage from free-living nematodes that feed on fungi to obligate plant parasitic nematodes.Based on the facts that D.destructor can feed on fungi and has a relatively short life cycle, and that it has similar features with both C.elegans and sedentary plant parasitic nematodes from clade 12, we propose it as a new model to study the biology, biocontrol of plant nematodes,and the interaction between nematodes and plants.