Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 16, 2000
Publication Date: N/A
Interpretive Summary: More than 100 species of small worms, known as plant-parasitic nematodes, infect nearly every agronomic and horticultural plant important to agriculture. In the United States, these pests cause annual economic losses from decreased food, fiber, and ornamental production estimated at $10 billion. One problem with developing safe, biologically based alternatives to the chemical nematicides that sometimes contaminate groundwater is that little is known about the biology of these nematodes. The current study describes a procedure that uses microwave irradiation, produced by an ordinary kitchen microwave, to prepare nematodes and plant infested roots so that they can be magnified several thousand times and observed in a powerful microscope known as a transmission electron microscope. Comparing plants that are resistant to nematodes with those that are susceptible will provide clues that scientists can use to develop methods to control these pests. This information will eventually benefit the public when the resulting technology provides an alternative to chemical nematicides.
Microwave irradiation of glutaraldehyde immersed samples was evaluated for the chemical fixation of galls that resulted from the infection of tomato roots (Lycopersicon esculentum) by the root-knot nematode (Meloidogyne incognita). Observation by transmission electron microscopy indicated that the best results were obtained when vials containing the intact galls were immersed in buffered glutaraldehyde and irradiated for 10 seconds and allowed to cool for 30 seconds; this procedure was repeated two additional times. This method provided results that enabled evaluation and photography of fine-structural details. The cortical cells of the root displayed no indication of osmotic stress. All organelles in the giant cells appeared normal and well fixed. Cross sections near the center of the gall showed that the hypodermis of the nematode was not separated from the cuticle which in turn was appressed to the outer cell walls of the giant cells. No obvious evidence of shrinkage, distortion or failure of resin infiltration in the adult nematode was apparent. High magnifications indicated that the fine structural features of the nematode were also well preserved. These results showed that immersion fixation combined with microwave irradiation improved fixation of older tissues and enabled preservation of stages and feeding sites that could not be easily obtained by conventional methods.