cis -Jasmone as allelopathic agent in inducing plant defence

The study of plant/insect interactions, particularly in multitrophic systems, it is possible to identify the insect semiochemicals that may induce defence responses in plants. From such work, cis-jasmone was identified as having highly specific and persistent effects in regulating the expression of genes associated with plant defence. The molecular genetic mechanisms involved are being investigated in Arabiclopsis thaliana by microan-ay analyses, the use of knockout lines and by functional gene expression studies in A. thallana and other systems. In cereals, there are major varietal differences in the level of defence induced by cis¬-jasmone. With some elite cultivars, long term protection against aphids has been established in the field. Chemical studies and investigations with insects using electrophysiological and behavioural assays have shown that 6-methy1-5-hepten-2-one, the production of which is induced by cis-jasmone, is highly active in reducing aphid colonisation and increasing foraging by parasitoids. Differential induction between cultivars may provide a useful means to elucidate the associated genetics. In both wheat and barley, there is additionally an induction with cis-jasmone of antibiotic effects against aphids. In wheat, this appears to be due to enhanced production of hydroxamic acids. For these secondary metabolites, the associated genes are known and RT-PCR is used to determine the induction of expression. MS", after derivatisation and chromatography, provides analytical tool to estimate these and unknown antibiotic agents in barley.