Computer tracking as a behavioral GC detector: Nematode responses to vapor of host roots.

A computer tracking system previously developed for studying the behavioral responses of nematodes to volatile stimuli was modified so that the effluent of a gas chromatograph passed over the nematodes while their behavior was analyzed. Since the behavior of several hundred nematodes can be analyzed simultaneously, this technique has the potential to provide a sensitive assay for behaviorally active fractions from the GC. This potential was tested with infective juveniles of the root-knot nematodeMeloidogyne incognita and vapor from the roots of host tomato plants. Direct injection of 1 ml of vapor led to reproducible responses at times corresponding to nitrogen plus oxygen elution and to carbon dioxide elution. Experiments with pure gases demonstrated responses to oxygen and to carbon dioxide. Attempts were made to find less volatile and less active components by pulling large volumes of vapor through a trap of Tenax GC and subsequently eluting them onto the GC. This approach did not lead to the detection of other activities. We conclude that, other than carbon dioxide, there are no volatile stimuli released from host roots in effective quantities.