Negative phototaxis in M. incognita

Phototaxis is a well-known behavior in many animals. However, little is known whether nematodes living in soil recognize light. Meloidogyne incognita is one of the most important root-knot nematode pests in the world. It has a very wide host range and can infect almost all plant species. Here, we examined the phototactic response in M. incognita. Negative phototactic behavior was observed in M. incognita on an agar plate. Nematodes responded by avoiding white light and blue light more than red light on agar plates. Light avoidance behavior of the nematodes was examined by microscopic analysis, and the nematodes escaped from near ultraviolet light (365 nm) in only approximately 3.2 seconds. They also avoided blue (470 nm), blue-green (500 nm), and green (550 nm) light in approximately 4.1, 7.4, and 10.0 seconds, respectively. These results suggest that M. incognita exhibits negative phototaxis, in particular, responding efficiently to shorter wavelength of light.