PARENT SESSION
Oral Session #45: Herbivory: Effects on Plants. Presiding: T. Craig.
Wednesday, August 8, 2001. 8:00 AM to 12:00 PM. Hall of Ideas H.
Jasmonic acid mediates indirect resistance.
Thaler, Jennifer1, Dicke, Marcel2, 1 2
ABSTRACT- Plants damaged by herbivorous insects can release volatile compounds and become more attractive to the natural enemies of herbivores. This volatile release is an induced response, perhaps regulated by the same signalling pathway, the jasmonate pathway, that regulates production of direct defenses against herbivores. In field grown tomato plants, caterpillars feeding on plants with induced responses activated experienced higher rates of parasitism. The purpose of this study was to determine if this increase in parasitism was due to the production of volatile compounds regulated by the jasmonate pathway. Using a Y-tube olfactometer, we found that plants damaged by herbivores were more attractive to predatory mites than undamaged plants. This indicates that damaged plants release a volatile blend detected by the predatory mites. In addition, we tested whether the jasmonate pathway was responsible for this increased attractiveness by comparing the attractiveness of wild-type and jasmonate-deficient mutants. The wild-type plants were more attractive to predatory mites when damaged whereas the jasmonate-deficient mutants were not more attractive when damaged. The attractiveness of the damaged jasmonate deficient mutants was recovered when these plants were sprayed with exogenous jasmonic acid. This indicates that the jasmonate pathway is responsible for the production of volatile compounds attractive to predators.
KEY WORDS: predatory mite, volatile, indirect defense, tomato