title: Something in the air? The impact of volatiles on mollusc attack of oilseed rape seedlings.
abstract: Mounting concerns about balancing food security with the environmental impacts of agro-chemical use underpin the need to better understand the mechanisms by which crop plants, particularly during the vulnerable seedling stage, attract or repel herbivores.
  
  
  
  The feeding preferences of the mollusc Helix aspersa were determined for several oilseed rape (Brassica napus) cultivars and a rank order of acceptability was established. This was compared with glucosinolate concentrations and volatile organic compound (VOC) profiles to determine whether seedling acceptability to molluscs was linked to either form of defence.
  
  
  
  While VOC profiles for each oilseed rape cultivar could be separated by canonical discriminant analysis and associated with mollusc feeding preferences, glucosinolate profiles were unrelated to snail feeding behaviour. A mixture of monoterpenes (α-pinene, β-myrcene and δ-3-carene) was identified as a putative attractant, while a blend of the green leaf volatiles 3-hexen-1-ol, 3-hexen-1-ol acetate and the monoterpene α-terpinene was identified as a putative repellent mix. Added to the VOC profile of oilseed rape seedlings, the 'repellent' mix reduced mollusc selection, while the 'attractant' mix had no effect.
  
  
  
  Despite the widespread assumption that seedling selection by generalist herbivores is governed by chemical defence and taste, we show that olfactory cues may be more important. Oilseed rape may be atypical of wild plants, but our ability to identify repellent volatile organic compounds that can influence snail olfactory selection points to new methods for crop protection using modified VOC profiles during the vulnerable seedling stage.
authors.affiliation: School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK, Centre for Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK, mehanley@plymouth.ac.uk.
authors.forename: Roger W R
authors.initials: RW
authors.lastname: Shannon
authors.affiliation: School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.
authors.forename: Anne-Emmanuelle
authors.initials: AE
authors.lastname: Félix
authors.affiliation: Centre for Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK.
authors.forename: Guy M
authors.initials: GM
authors.lastname: Poppy
authors.affiliation: Centre for Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK.
authors.forename: Philip L
authors.initials: PL
authors.lastname: Newland
authors.affiliation: German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany, Institute of Ecology, Friedrich Schiller University Jena, Dornburger-Str. 159, 07743 Jena, Germany and Molecular Interaction Ecology, Institute of Water and Wetland Research (IWWR), Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: van Dam
authors.affiliation: School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK, mehanley@plymouth.ac.uk.
authors.forename: Mick E
authors.initials: ME
authors.lastname: Hanley
mesh_terms: D000818:Animals; D029688:Brassica napus / Q000737:chemistry* / Q000502:physiology*; D018556:Crops, Agricultural; D005247:Feeding Behavior; D005961:Glucosinolates / Q000032:analysis*; D006372:Helix, Snails / Q000502:physiology*; D060434:Herbivory; D018515:Plant Leaves / Q000737:chemistry; D036226:Seedlings / Q000737:chemistry / Q000502:physiology; D055549:Volatile Organic Compounds / Q000032:analysis* / Q000737:chemistry
chemical_list: D005961:Glucosinolates; D055549:Volatile Organic Compounds
keywords: Brassica napus L.; Brassicaceae; Helix aspersa Müller; crop protection; food security; green leaf volatiles; monoterpenes; plant volatiles; seedling herbivory; solid-phase microextraction