Abstract:
The sugar beet cyst nematode, Heterodera schachtii, is a major agricultural pest.
The disruption of the mating behaviour of this plant parasite in the field may provide a
means of biological control, and a subsequent increase in crop yield. The H. schachtii
female sex pheromone, which attracts homospecific males, was collected in an aqueous
medium and isolated using high performance liquid chromatography. Characterization of
the male-attractive material revealed that it was heat stable and water soluble. The
aqueous medium conditioned by female H. schachtii was found to be biologically active
and stimulated male behaviour in a concentration dependent manner. The activity of the
crude pheromone was specific to males of H. schachtii and did not attract second stage
juveniles. Results indicated that vanillic acid, a putative nematode pheromone, is not an
active component of the H. schachtii sex pheromone. Male H. schachtii exhibited stylet
thrusting, a poorly understood behaviour of the male, upon exposure to the female sex
pheromone. This behaviour appeared to be associated with mate-finding and was used as
a novel indicator of biological activity in bioassays. Serotonin, thought to be involved in
the neural control of copulatory behaviour in nematodes, stimulated stylet thrusting.
However, the relationship between stylet thrusting induced by the sex pheromone and
stylet thrusting induced by serotonin is not clear. Extracellular electrical activity was
recorded fi-om the anterior region of H. schachtii males during stylet thrusting, and
appeared to be associated with this behaviour. The isolation of the female sex
pheromone of H. schachtii may, ultimately, lead to the structural identification and
synthesis of the active substance for use in a novel biological control strategy.
