Still armed after domestication? Impact of domestication and agronomic selection on silicon defences in cereals

1. Plant phenotypes reflect trade-offs between competing resource-intensive physiological processes. A shift in resource allocation, away from anti-herbivore defences and towards growth and reproduction, is predicted through plant domestication, such that crops are faster growing and higher yielding than their wild ancestors. These changes are hypothesized to have come at the cost of defence investment, leaving crops ‘disarmed by domestication’. Silicon is the principal anti-herbivore defence in grasses, including many of our most important staple cereal crops, but the impact of domestication on silicon-based defences is unknown. 2. We measured the effects of both domestication and modern agronomic selection on growth rate and a suite of anti-herbivore defences, specifically leaf toughness, silicon and phenolic concentrations. Our comparison of wild, landrace and modern cultivated cereals spanned multiple cereal species, including wheat, barley and maize, sampling eight independent dome...