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Silene floral and deterrent signals

Final Report Summary - FLORDETERSIGNALS (Silene floral and deterrent signals)

Project context and objectives

The objectives of part B:

1. Do the floral odours of Silene plants change after egg deposition or seed consumption by the larvae of Handena bicruris?
Volatile organic compounds (VOCs) were found to change after Handena bicruris eggs were deposited. The control plants released significantly more lilac aldehyde A, B, C and D and veratrole than plants with eggs. The exposure of uninjured plants to infestations in the second part of our experiment resulted in a rather low VOC induction.

2. a) Do vegetative odours of Silene plants change with larval consumption of seeds?

The researcher noticed that there was no connection between larval consumption and odour releasing; larvae were actively eating on the seeds. However, no signal was seen on the gas chromatography- mass spectrometry (GC-MS) chromatograms. The researcher suspected that the plants were too old to produce and release odours. Actively growing crop plants (cereals) release odours at BBCH 32-49. After BBCH 49, crop plants do not produce and release volatiles. The researcher suggested that there is a similar situation with Silene plants.

b) Do the induced changes vary in populations with different abundances of co-pollinators?

The researcher was working on Autographa gamma and Hadena bicruris (both pollinators). With Autographa gamma, the changes in VOC production were very low and not significant. However, it was a different situation with Hadena bicruris. After pollination, the plant significantly restricted the production of attractant. The changes in VOC production were different following the abundance of co-pollinators. Pollinated plants (by Autographa gamma and Hadena bicruris) also restricted the production of attractants. The researcher found that there was a decrease in the total scent emission after pollination.

c) Do the Silene plants produce repellent compounds against Hadena and/or attractive compounds for their natural enemies?

There were compounds (ß-pinene, ß-myrcene, (Z)-ocimene, ß-caryopyllene and (E)-ß-farnesene) that were released in larger amounts after egg depositions but surprisingly the production of attractants (lilac aldehyde A, B, C and D and veratrole) were significantly reduced. As a result, the adults of Hadena bicruris did not deposit any more eggs.

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