Summary1. In nature, the fruit fly Drosophila melanogaster is attracted to fermenting fruit. Micro-organisms like Saccharomyces yeasts growing on fruit occupy a commonly overlooked trophic level between fruit and insects. Although the dietary quality of yeast is well established for D. melanogaster, the individual contribution of fruit and yeast on host finding and reproductive success has not been established. 2. Here, we show that baker's yeast Saccharomyces cerevisiae on its own is sufficient for fruit fly attraction, oviposition and larval development. In contrast, attraction and oviposition were significantly lower if non-fermented grape juice or growth media were used, and yeast-free grapes did not support larval development either. 3. Despite a strong preference for fermented substrates, moderate attraction to and oviposition on unfermented fruit might be adaptive in view of the fly's capacity to vector yeast. 4. Signals emitted by fruit were only of secondary importance because fermenting yeast without fruit induced the same fly behaviour as yeast fermenting on fruit. We identified a synthetic mimic of yeast odour, comprising ethanol, acetic acid, acetoin, 2-phenyl ethanol and 3-methyl-1-butanol, which was as attractive for the fly as fermenting grape juice or fermenting yeast minimal medium. 5. Yeast odours represent the critical signal to establish the fly-fruit-yeast relationship. The traditional plant-herbivore niche concept needs to be updated, to accommodate for the role of micro-organisms in insect-plant interactions.

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Summary CYP3RNA, a double‐stranded (ds)RNA designed to concomitantly target the two sterol 14α‐demethylase genes FgCYP51A and FgCYP51B and the fungal virulence factor FgCYP51C, inhibits the growth of the ascomycete fungus Fusarium graminearum (Fg) in vitro and in planta. Here we compare two different methods (setups) of dsRNA delivery, viz. transgene expression (host‐induced gene silencing, HIGS) and spray application (spray‐induced gene silencing, SIGS), to assess the activity of CYP3RNA and novel dsRNA species designed to target one or two FgCYP51 genes. Using Arabidopsis and barley, we found that dsRNA designed to target two FgCYP51 genes inhibited fungal growth more efficiently than dsRNA targeting a single gene, although both dsRNA species reduced fungal infection. Either dsRNA delivery method reduced fungal growth stronger than anticipated from previous mutational knock‐out (KO) strategies, where single gene KO had no significant effect on fungal viability. Consistent with the strong inhibitory effects of the dsRNAs on fungal development in both setups, we detected to a large extent dsRNA‐mediated co‐silencing of respective non‐target FgCYP51 genes. Together, our data further support the valuation that dsRNA applications have an interesting potential for pesticide target validation and gene function studies, apart from their potential for crop protection.

Using HPLC, forty-five phloroglucinol derivatives were obtained from an ethanolic extract of the brown alga Carpophyllum angustifolium after peracetylation. Compounds of the fuhalol-B series are described. The structure of hydroxyheptafuhalol-B nonadecaacetate is confirmed by the addition of (13)C NMR spectral data, octafuhalol-C heneicosaacetate is described for the first time. The occurrence of four halogenated phlorotannins is reported: 2-chlorophloroglucinol triacetate, 2[D']iododiphlorethol pentaacetate, which had been isolated formerly only as a mixture, 3[A]chlorobifuhalol hexaacetate, and 3[A(4)]chlorodifucol hexaacetate. All substances were characterized by means of spectral analysis.