Electrophysiological analysis of sensory responses and stylet activity of second stage juveniles of Globodera rostochiensis, and plant reactions to nematode invasion

摘要

Electrophysiological techniques have been used to examine nematode sensory responses and stylet protractor muscle activity, and the electrical signals generated in plants in response to nematode invasion. Examples of these three uses of electrophysiolo-gy with second-stage juveniles (J2s) of Globodera rostochiensis are presented. The concentration-dependent sensory responses of J2s to acetylcholine were examined and the delay in response was quantified. Stimulation of J2s with potato root dif-fusate(PRD) elicited significant increases in spike activity, whereas non-host root dif-fusate and female sex pheromones elicited no response. Incubating J2s in an amphid-spe-cific antibody and in DiTera~(R), a biological nematicide, blocked the response to PRD. Electropharyngeogram (EPG) analysis of stylet protractor muscle activity in response to various concentrations of serotonin were obtained and correlated with stylet movement using video analysis. The antagonist, gramine, incorporated with serotonin, almost completely eliminated stylet thrusting and prior exposure of J2s to DiTera~(R) significantly reduced subsequent stylet activity. Distinct patterns of electrical activity were recorded from the roots of susceptible and resistant potato cultivars after applying J2s. More marked responses were obtained from susceptible roots than from resistant roots. Electrical activity in response to mechanical and bacterial exoenzyme stimuli did not account for the electrical activity recorded from susceptible roots.