Several Paratrichodorus and Trichodorus (trichodorid) nematode species are natural vectors of Tobacco rattle virus (TRV) and cause economically important diseases, especially in potato and ornamental bulbous crops. Identification of trichodorid species based on morphological characters is laborious, time-consuming, and requires the services of highly trained personnel. Molecular diagnostics for trichodorid nematodes, using the ribosomal DNA repeat unit, were successfully developed to distinguish two Paratrichodorus and two Trichodorus species. The complete sequences of the 18S genes and the ITS-1 regions for these species were obtained and species-specific primers successfully designed for them. An RT-PCR assay was developed utilizing isolate-specific primers that amplify serologically distinguishable strains of TRV in individual trichodorid nematodes. The primers were based on the highly conserved RNA-1 segment of the bipartite genome and also on different parts of the RNA-2 segment of the virus genome.

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The specificity of the interaction between the coat protein (CP) and 2b nematode-transmission helper protein of two isolates, PpK20 and PaY4, of Tobacco rattle virus (TRV) that differ in their transmission characteristics was investigated. Yeast two-hybrid experiments identified a central domain of the CP that promoted CP:CP interaction but inhibited CP:2b interaction. Deletion of a conserved coiled-coil domain from the 2b protein prevented its interaction with CP, whereas deletion of N- and C-terminal domains of the 2b protein greatly enhanced its interaction with CP. A C-terminal flexible domain of the CP was also shown to be important for interaction with the 2b protein. However, this domain was not sufficient to direct isolate-specific interaction of these proteins either in yeast or via a chimeric TRV in planta. Although these two TRV isolates are both transmitted by a shared vector trichodorid nematode, Paratrichodorus pachydermus, the CP from isolate PpK20 did not interact with the 2b protein from isolate PaY4, and vice versa, suggesting that in the field mixed infections of TRV are unlikely to cause promiscuous transmission by alternative trichodorid nematode species.

Lectins and polyclonal antiserum that bind specifically and reproducibly to the overall surface of Paratrichodorus anemones were identified and bound to monodisperse superparamagnetic particles (Dynabeads) to assess their efficiency as probes for capturing target nematodes from test suspensions. In recovery experiments, while both types of probe isolated nematodes, antibody-coated beads recovered them more efficiently than beads coated with lectins. When immunomagnetic capture was used to isolate P. anemones from mixtures of naturally occurring populations of nematodes extracted in bulk, from soil samples, 80% of the target nematodes were recovered.