Transfer of chemical defence from rye to clover is associated with enhanced clover resistance against root‐knot nematodes

Interspecific root interactions are obviously important features of natural, diverse plant communities and cocropping systems. Yet, the implications of interspecific exchange of bioactive plant metabolites for plant defence are not clear. We hypothesise that cocropped heterospecific plants exchange defence compounds, thereby enhancing plant defence against pests. This study investigated the metabolome of white clover grown as a monocrop and cocropped with rye. We used targeted and untargeted mass spectrometry-based metabolomics to elucidate whether the transfer of bioactive compounds enhances clover defence against root-knot nematode invasion and reproduction. Our findings revealed that eight benzoxazinoids (BXs), a group of bioactive compounds produced by rye, were absorbed by clover roots, with three BXs translocated to the shoots. Cocropping and the root uptake of BXs altered the clover metabolome. These metabolic changes, along with BX transfer, significantly enhanced clover root defence against Meloidogyne incognita invasion and reproduction. Overall, this study provides novel insights into how specialised metabolites, such as BXs, mediate interspecific root interactions, ultimately improving plant defence in cereal-legume intercropping systems.