title: Salinity-mediated cyanogenesis in white clover (Trifolium repens) affects trophic interactions.
abstract: OBJECTIVE
  Increasing soil salinity poses a major plant stress in agro-ecosystems worldwide. Surprisingly little is known about the quantitative effect of elevated salinity on secondary metabolism in many agricultural crops. Such salt-mediated changes in defence-associated compounds may significantly alter the quality of food and forage plants as well as their resistance against pests. In the present study, the effects of soil salinity on cyanogenesis in white clover (Trifolium repens), a forage crop of international importance, are analysed.
  
  
  METHODS
  Experimental clonal plants were exposed to five levels of soil salinity, and cyanogenic potential (HCNp, total amount of accumulated cyanide in a given plant tissue), β-glucosidase activity, soluble protein concentration and biomass production were quantified. The attractiveness of plant material grown under the different salt treatments was tested using cafeteria-style feeding trials with a generalist (grey garden slug, Deroceras reticulatum) and a specialist (clover leaf weevil, Hypera punctata) herbivore.
  
  
  RESULTS
  Salt treatment resulted in an upregulation of HCNp, whereas β-glucosidase activity and soluble protein concentration showed no significant variation among treatments. Leaf area consumption of both herbivore species was negatively correlated with HCNp, indicating bottom-up effects of salinity-mediated changes in HCNp on plant consumers.
  
  
  CONCLUSIONS
  The results suggest that soil salinity leads to an upregulation of cyanogenesis in white clover, which results in enhanced resistance against two different natural herbivores. The potential implications for such salinity-mediated changes in plant defence for livestock grazing remain to be tested.
authors.affiliation: Portland State University, Department of Biology, 1719 SW 10th Avenue, Portland, OR 97201, USA ballhorn@pdx.edu.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Ballhorn
authors.affiliation: Portland State University, Department of Biology, 1719 SW 10th Avenue, Portland, OR 97201, USA.
authors.forename: Jacob D
authors.initials: JD
authors.lastname: Elias
mesh_terms: D000818:Animals; D018533:Biomass; D003486:Cyanides / Q000378:metabolism*; D017753:Ecosystem; D049851:Gastropoda / Q000502:physiology; D060434:Herbivory; D018515:Plant Leaves / Q000502:physiology; D054712:Salinity; D012987:Soil; D029921:Trifolium / Q000254:growth & development / Q000502:physiology*; D048889:Weevils / Q000502:physiology
chemical_list: D003486:Cyanides; D012987:Soil
keywords: Bottom-up effects; HCNp; Trifolium repens; cyanide; cyanogenesis; cyanogenic glucoside; forage crop; herbivore; secondary metabolite; trophic interactions; white clover; β-glucosidase