Ontwikkeling van een methode voor de veredeling van komkommer op versterkte aantrekking van biologische bestrijders (WPB.5479)

Project nummer: wpb5479

Omschrijving van het onderzoek

Environmentally benign crop protection can employ host plant resistance and biological control. These two methods of crop protection are not by definition synergistic. Crop characteristics can have an important influence on the success of biological control, but so far plant breeders have never selected for these. It is important that the biological control agents can find the herbivores at low densities. An important plant characteristic that influences the searching success is the herbivore-induced production of plant volatiles, that the plants use to defend themselves indirectly against the herbivores by attracting carnivorous enemies of herbivores. This indirect defence is induced by herbivory but not by mechanical damage. It involves the de novo biosynthesis of plant volatiles and has been documented for a considerable number of plant species. Among the induced plant volatiles, terpenes are the dominant group and among these the C11-homoterpene 4,8-dimethyl-1,3(E),7-nonatriene has been recorded frequently as one of the major compounds. This compound attracts carnivorous arthropods such as predatory mites, that are effective natural enemies of spider mites. We have recently demonstrated that a spider- mite inducible (3S)-(E)-nerol idol synthase in cucumber and lima bean is the key regulatory enzyme in the induced biosynthesis of the C1 1 -homoterpene (Bouwmeester et al. 1999). Preliminary results indicate the possibility to clone the gene encoding this key enzyme. This will enable a breakthrough in the investigation of the application of herbivore-induced indirect defence mediated by plant volatiles.
In the study of herbivore-induced indirect defence, an important obstacle is the absence of a meaningful set of test and control plants, i.e. plants that differ only in the ability to induce carnivore attractants, but are the same in all other respects. A molecular approach is the only way to obtain such plant combinations and our recent breakthrough in the identification of a key enzyme and the possibility of cloning it provide a unique opportunity to obtain plants that do, plants that do not and plants that produce more of the C1 1 -homoterpene. A preliminary experiment with seven different cucumber accessions showed that there is a strong variation in the production of volatiles both after spider mite infestation as well as after the application of jasmonic acid (Bouwmeester, Verstappen and Dicke, unpublished results): This implies that there is a large genetic variation present in cucumber which should enable progress in a breeding programme for improved volatile production.
The results from the proposed project will lead to more insight in the molecular pathway that is involved in spider-mite induced release of volatiles. This is an exciting and innovative opportunity to demonstrate the ecological significance of these induced volatiles and in the long run their importance for the realisation of a sustainable agriculture with a reduced use of pesticides. The insights obtained can be used by seed companies to improve their crops with respect to integration with biological control through gene/marker assisted conventional breeding. The identified genes involved in the biosynthesis of herbivory-induced volatiles can be used as markers to screen plants in a very young stage for their expression patterns under different environmental conditions. High expressor lines in spider-mite induced volatiles can then be used in a traditional breeding programme. It is important to stress that this proposal does not aim at introducing transgenic crops. Instead, knowledge at the molecular level will be used to improve crops through conventional plant breeding practices.

Gebruikers

Er zijn twee bedrijven bij dit project betrokken.

Projectleider

Prof.dr. M. Dicke

Wageningen Universiteit Plantenwetenschappen

Postbus 8031 6700 EH Wageningen

Status van het project

Gestart	: 01-08-2002
Einddatum	: 01-08-2007

Trefwoorden

Biologische bestrijding, Food & Flowers, Moleculaire biologie, Plantenfysiologie, Plantenveredeling.

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