Root uptake of umbelliferone enhances pea's resistance against root-knot nematodes

Coumarins are secondary plant metabolites which play a key role in plant–plant and plant–microbe interactions. In particular, they are highly involved in environmental stress responses. Coumarins can transfer from plants producing coumarins to non-coumarin-producing neighbouring plants. As in vitro studies have shown that coumarins are nematicidal, we hypothesized that this transfer may also result in enhanced resistance against plant parasitic nematodes in coumarin-receiving plants. To test if the uptake of coumarins in a non-coumarin- producing plant protects the plant against nematode attack, we incubated non-coumarin- producing pea seedlings in growth media with the coumarin umbelliferone for three weeks, after which the plants were transplanted into soil and inoculated with root-knot nematodes (Meloidogyne incognita). We quantified the coumarin content in pea organs and nematode root invasion 2, 4, and 6 weeks after transplantation. Umbelliferone was taken up by the pea roots and translocated to the shoots. As a result of metabolization, umbelliferone and its derived metabolites coumarin, scopoletin, and scopolin were detected in the plants. The root uptake of umbelliferone reduced root-knot nematode invasion significantly up to 4 weeks after the root exposure. Our results suggest that the root uptake and the transfer of bioactive compounds between plants can expand the understanding of plant–plant interactions.