Analysis of chemosensory responses of second stage juveniles of Globodera rostochiensis using electrophysiological techniques

Eleclrophysiological techniques were developed to obtain recordings of electrical activity from the anterior end of live, second stage juveniles (J2) of Globodera rostochiensis. Sequential exposure of individual J2 to test semiochemicals was also possible using a modified perfusion system. Concentration-dependent responses were obtained from J2 during exposure to 0.1, 1, 10 and 100 mM acetylcholine. The delay before any response was not concentration-dependent. The responses to 10 mM concentrations of several chemicals known to elicit a feeding response in insects were assessed. There was a significant increase in spike activity When J2 were exposed to D-tryptophan but glycine and citric acid elicited no responses. Exposure to D-glutamic acid resulted in a significant increase in spike activity but exposure to the L-isomer gave no response. This was confirmed by sequential exposure of J2 to the L- then to the D-isomer. Exposure to potato root diffusate elicited a response, whereas a non-host root diffusate from sugar beet and female secretory-excretory (S-E) product caused no change in activity.