Leafhoppers were attracted by growing alfalfa (Medicago sativa), one of their favorite host plants. When the alfalfa plants were highly infested, they were cut down to motivate the leafhoppers to move into the tobacco field, which was adjacent to the alfalfa field. The following parameters were recorded: The prevalence and intensity of leaf damage on the individual lines and control plants, the corresponding jasmonate levels, the concentration and the occurrence of defense toxins, and finally the release of specific volatiles to indirectly fend off herbivores. Experiments conducted in the glasshouse back in Jena, Germany, were designed to quantify Empoasca leaf damage on transgenic plants, whose inability to produce jasmonate had been compensated for by applying jasmonate on their leaves. "We were able to demonstrate that leafhoppers' preferred to feed on plants that were incapable of jasmonate signaling. Whether other defense substances, such as the toxin, nicotine, or digestion inhibitors, were present or not, was entirely irrelevant," says Mario Kallenbach, who carried out these experiments.
The Leafhoppers could be used as "bloodhounds" to identify natural mutants in wild tobacco populations
These results demonstrated that Empoasca leafhoppers select their food plants after probing the leaves using their mouthparts to find out whether plants are ready for defense. Or more precisely: whether the jasmonate-based hormonal system responsible for signaling herbivory and initiating defenses is functional or even present. If this is the case, the insect leaves the plant and causes no further damage. If jasmonate-signaling is defective, the plant is selected for feeding (see pictures). Interestingly, l
|Contact: Ian T. Baldwin|
Max Planck Institute for Chemical Ecology