New herbal bioactives against whitefly.
Glandular trichomes of the wild tomato species Solanum habrochaites produce a variety of defense substances against different aggressors. The substance 7-epizingiberene, for example, provides an effective protection against whitefly and other insect pests. Scientists at IPB, together with partners from industry, have now discovered two new derivatives of 7-epizingiberene: 9-hydroxy-zingiberene (9HZ) and 9-hydroxy- 10,11-epoxyzingiberene (9H10epoZ). Both compounds were isolated from S. habrochaites trichomes and subsequently characterized. Using a transcriptomics approach, the Halle researchers could also identify a gene coding for a cytochrome P450 oxygenase, which is involved in the biosynthesis of these zingiberene derivatives. In enzyme assays following transient gene expression in tobacco, the oxygenase was shown to catalyze two successive oxidations that convert 7-epizingiberene to its derivatives 9HZ and 9H10epoZ. Particularly the 9H10epoZ proved to be highly effective against whitefly in bioactivity assays. The defense compound exhibited also strong toxic activities against various microorganisms, such as the causal agent of late blight Phytophthora infestans and the causal agent of gray mold Botrytis cinerea.
With this study, the research team proved once again that trichome secretions from wild tomatoes provide effective protection against various harmful organisms. Although wild tomatoes are not as high-yielding as cultivated tomatoes, they are more resistant against insect pests due to the number, structure and functionality of their glandular trichomes on leaves and stems. The availability of all required genes for the biosynthesis of 7-epizingiberene and its derivatives makes it possible to introduce this insect resistance trait in cultivated tomatoes by precision breeding.