Submitted to: Journal of Nematology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/4/2008
Publication Date: 9/1/2008
Citation: Skantar, A.M., Carta, L.K., Handoo, Z.A. 2008. Molecular and morphological characterization of an unusual Meloidogyne arenaria population from traveler’s tree Ravenala madagascariensis. Journal of Nematology. 40(3):179-189. Interpretive Summary: Nematodes are microscopic worms that cause ten billion dollars of crop losses in the United States each year. Root-knot nematodes are an important group of nematodes that damage many kinds of plants by invading the roots and interfering with nutrient uptake. Identifying these nematodes can be difficult because different species often look alike and because their complex genetic composition has impeded the development of molecular methods for their identification. In the present study, ARS scientists used anatomical and molecular data to identify an unusual variant of root-knot nematode that was found on an ornamental plant from a public arboretum in Pennsylvania. The results are significant because they demonstrate the utility and limitations of several molecular markers and anatomical traits often used for distinguishing look-alike root-knot nematode variants. Consequently, scientists, action agencies, and extension agencies engaged in nematode research and control will use this research.
Technical Abstract: An unusual Meloidogyne arenaria population was discovered on roots of a traveler’s tree (Ravenala madagascariensis) intended for display at a public arboretum in Pennsylvania. The population aroused curiosity by the lack of visible galling on the roots of the infected plant, and the females were typically surrounded by egg sacs. Molecular characterization included analysis of four markers. The mitochondrial sequence extending from cytochrome oxidase II (COII) to the 16S (1RNA) gene was nearly identical to one from M. arenaria and close to sequences from M. morocciensis and M. thailandica. The ribosomal intergenic spacer (IGS) sequence shared greatest similarity to those from M. thailandica, M. incognita, and M. floridensis. The 28S D2-D3 expansion segment was closest to those from M. arenaria, M. incognita, and M. paranaensis. Partial Hsp90 genomic sequence revealed greatest similarity between the palm isolate and M. thailandica, or an Hsp90 haplotype from M. floridensis. Most morphometrics of the traveler palm population fit within the ranges reported for M. arenaria, with some features consistent with M. morocciensis, M. incognita or M. javanica. Considering the well-known morphological variability among M. arenaria populations and the relatively small genetic distances separating these Meloidogyne species for all DNA markers examined, the evidence is most consistent with a diagnosis of M. arenaria.