Chemotaxis assay of plant-parasitic nematodes on a gel-filled microchannel device

•On-chip chemotaxis assay method of plant-parasitic nematodes was developed.•A protocol to allow the nematodes to move around in the microchannels was achieved.•Potassium nitrate stimulated the behavior of plant-parasitic nematode M. incognita.•Potassium nitrate caused attraction or repulsion depending on its concentration. Plant-parasitic nematodes substantially damage a wide variety of agricultural crops worldwide. The chemotaxis of nematodes is a key factor in their parasitic relationship with plants. Therefore, studies on nematode chemotaxis are essential for devising efficient and environmentally friendly management methods. In this paper, we report a new, efficient, and quantitative method to analyze chemotaxis of the plant-parasitic nematode, Meloidogyne incognita, using a gel-filled microchannel device. We quantitatively defined time-dependent concentration gradients of chemicals in the gel-filled microchannel by measuring changes in the fluorescence intensity of fluorescein. We also developed a protocol to allow the nematodes to move around in the microchannels by loading an agarose gel with optimum concentration. Using this novel assay method, we have shown that potassium nitrate (KNO3) stimulates the behavior of M. incognita and can have both repellent and attractant effects, depending on the concentration gradient. This newly developed quantitative chemotaxis assay method can be used to screen and identify new candidate molecules that repel or attract nematodes, and also to analyze the repellent/attractant properties of those molecules toward nematodes.