Chemical defence in Brassicaceae against pollen beetles revealed by metabolomics and flower bud manipulation approaches

• Published in: Plant, cell and environment cell and environment, 2021-02, Vol.44 (2), p.519-534
• Main Authors: Austel, Nadine, Böttcher, Christoph, Meiners, Torsten
• Format: Article
• Language: English
• Subjects: Antifeedants; Beetles; Bioassays; Brassica; Brassicaceae; Chemical defense; Chemical industry; Chemical plants; Coleoptera; Cultivars; Divergence; Feeding; Flavonoids; Flow resistance; Flowers; genetic variation; Glucosinolates; herbivory; insect resistance; Insects; Metabolites; Metabolomics; non‐targeted metabolite profiling; Oilseeds; Oleanolic acid; Pest resistance; Phenylpropanoids; Plant breeding; plant defence; Plant resistance; Pollen; Rape plants; Rapeseed; Saponins; secondary metabolism
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13949

Divergence of chemical plant defence mechanisms within the Brassicaceae can be utilized to identify means against specialized pest insects. Using a bioassay‐driven approach, we (a) screened 24 different Brassica napus cultivars, B. napus resyntheses and related brassicaceous species for natural plant resistance against feeding adults of the pollen beetle (Brassicogethes aeneus), (b) tested for gender‐specific feeding resistance, (c) analysed the flower bud metabolomes by a non‐targeted approach and (d) tested single candidate compounds for their antifeedant activity. (a) In no‐choice assays, beetles were allowed to feed on intact plants. Reduced feeding activity was mainly observed on Sinapis alba and Barbarea vulgaris but not on B. napus cultivars. (b) Males fed less and discriminated more in feeding than females. (c) Correlation of the metabolite abundances with the beetles' feeding activity revealed several glucosinolates, phenylpropanoids, flavonoids and saponins as potential antifeedants. (d) These were tested in dual‐bud‐choice assays developed for medium‐throughput compound screening. Application of standard compounds on single oilseed rape flower buds revealed highly deterrent effects of glucobarbarin, oleanolic acid and hederagenin. These results help to understand chemical plant defence in the Brassicaceae and are of key importance for further breeding strategies for insect‐resistant oilseed rape cultivars. A metabolomics approach and a novel dual‐bud‐choice assay reveal saponins and glucosinolates from Barbarea vulgaris as mediators of gender‐specific resistance against the pollen beetle.