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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETIC AND CULTURAL METHODS TO MANAGE RENIFORM NEMATODE IN COTTON Title: Molecular and morphological characterization and biological control capabilities of a Pasteuria ssp. parasitizing Rotylenchulus reniformis, the reniform nematode

Authors
item Schmidt, Liesbeth -
item Hewlett, Thomas -
item Green, April -
item Simmons, Lee -
item Kelley, Karen -
item Doroh, Mark -
item Stetina, Salliana

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 12, 2011
Publication Date: September 1, 2010
Citation: Schmidt, L.M., Hewlett, T.E., Green, A., Simmons, L.J., Kelley, K., Doroh, M., Stetina, S.R. 2010. Molecular and morphological characterization and biological control capabilities of a Pasteuria ssp. parasitizing Rotylenchulus reniformis, the reniform nematode. Journal of Nematology. 42:207-217.

Interpretive Summary: Reniform nematode is a microscopic worm that causes economic losses in cotton, soybean, and other crops by feeding on plant roots. A bacterium in the genus Pasteuria that infects and kills reniform nematodes has been identified. Studies confirmed that this bacterium infects and completes its life cycle in juvenile, male, and female reniform nematodes. This bacterium is morphologically and genetically similar to other species of Pasteuria that have been shown to infect different nematode species. This species of Pasteuria can be grown in the lab and kills reniform nematode in controlled tests when formulated as a seed treatment or granular biological nematicide. As such, it has the potential to be further developed as a tool to manage reniform nematode in commercial fields.

Technical Abstract: Rotylenchulus reniformis is one of 10 described species of reniform nematodes and is considered the most economically significant pest within the genus, parasitizing a variety of important agricultural crops. Rotylenchulus reniformis collected from cotton fields in the Southeastern US were observed to have the nematode parasitic bacterium Pasteuria attached to their cuticles. Challenge with a Pasteuria-specific monoclonal antibody in live immuno-fluorescent assay (IFA) confirmed the discovery of Pasteuria infecting R. reniformis. Scanning and transmission electron microscopy were employed to observe endospore ultrastructure and sporogenesis within the host. Pasteuria spp. were observed to infect and complete their life-cycle in juvenile, male and female R. reniformis. Molecular analysis using Pasteuria species-specific and degenerate primers for 16s rRNA and spoil, and subsequent phylogenetic assessment, placed the Pasteuria associated with R. reniformis in a distinct clade within established assemblages for the Pasteuria infecting phytopathogenic nematodes. A global phylogenetic assessment of Pasteuria 16s rDNA using the Neighbor-Joining method resulted in a clear branch with 100% boot¬strap support that effectively partitioned the Pasteuria infecting phytopathogenic nematodes from the Pasteuria associated with bacterivorous nematodes. Phylogenetic analysis of the R. reniformis Pasteuria and Pasteuria spp. parasitizing a number of economically important plant parasitic nematodes revealed that Pasteuria with different host specificities are closely related and likely constitute biotypes of the same species. This suggests host preference, and thus effective differentiation and classification are most likely predicated by an influential virulence determinant(s) that has yet to be elucidated. Pasteuria Pr3 endospores produced by in vitro fermentation demonstrated efficacy as a commercial bionematicide to control R. reniformis on cotton in pot tests, when applied as a seed treatment and in a granular formulation. Population control was comparable to a seed-applied nematicide/insecticide (thiodicarb/imidacloprid) at a seed coating application rate of 1.0 x 108 spores/seed.

Last Modified: 10/23/2014
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