Submitted to: Journal of Nematology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/12/2006
Publication Date: 9/1/2006
Citation: Vovlas, N., Landa, B., Liebanas, G., Handoo, Z.A., Subbotin, S., Castillo, P. 2006. Characterization of the cystoid nematode meloidoderita kirjanovae (nemata: sphaeronematidae) from southern italy. Journal of Nematology. 38(3):376-382. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that cause global crop losses exceeding $100 billion annually. The cystoid nematodes are a poorly studied group of nematodes which can infect several valuable crop plants. One problem with determining the damage caused by specific cystoid nematodes is that methods for their identification are inadequately known. In this study, researchers from Italy, in collaboration with scientists from California and Spain and an ARS scientist from Beltsville, describe methods for identifying a cystoid nematode discovered on a mint. These methods involved anatomical features obtained with light microscopes and high-powered electron microscopes, as well as DNA sequences. The results indicated that this nematode could be identified by the shapes of the lip ridges, head, and lateral markings of juvenile nematodes, as well as the spines and surface markings on adults. The sequences of the genes known as ITS1 and 5.8S were also found to diagnose the identity of this species. The results are significant because they provide the details necessary for scientists to correctly identify this species wherever it may occur in the world. Therefore, this research will be used by research scientists, action agencies, and extension agencies engaged in nematode research and control.
Technical Abstract: A cystoid nematode population was detected parasitizing water mint (Mentha aquatica) in Southern Italy. Morphological, morphometric, and SEM studies identified the nematode as Meloidoderita kirjanovae. It was readily distinguished from the closely related species Meloidoderita polygoni with molecular approaches using the internal transcribed spacer 1 and 5.8S gene sequences of nuclear ribosomal DNA. The phylogenetic relationships of M. kirjanovae with related genera based on sequences of the D2-D3 expansion segments of the 28S nuclear ribosomal RNA gene supports position of the genus Meloidoderita together with Sphaeronema within the Criconematina clade, and justify the placement of Meloidoderita as member of the family Sphaeronematidae. Host-parasite relationship studies of the nematode in naturally infected water mint demonstrated that the nematode induces a typical syncytium within the stele tissues, modifying the structure of the pericycle. Syncytial formation led to extensive deformation of the vascular cylinder in some cases, as well as disorganization of the root cortex. Commonly, the nematode feeding sites comprised six to eight syncytial cells surrounding the nematode’s lip region, which possess enlarged nuclei, vacuolated cytoplasm, and a great number of organelles.