Induced responses to insect herbivory are a common phenomenon in the plant kingdom. So far, induced
responses have mostly investigated in aerial plant parts. Recently it was found that root herbivore may
also elicit both local and systemic responses affecting aboveground herbivores and their natural enemies.
Using broccoli (Brassica oleracea subsp. italica L.) and turnip (Brassica rapa subsp. rapa L.), two cultivated
brassicaceaous plants differing in their chemistry and morphology, we analysed the local and systemic
induced responses triggered by Delia radicum L. damage, JA and SA application. We also assessed whether
the root induction treatments affected D. radicum larval performance.
Both D. radicum damage and JA induced changes in glucosinolate and sugar content as well as affected D.
radicum performance, while SA application did not. Despite the uniform chemical responses, the effect on
larval performance on broccoli and turnip plantswas very different. On broccoli, JA root treatment reduced
herbivore performance, whereas in turnips the same treatment enhanced it. JA- and D. radicum-induced
responses followed similar patterns, which suggests that the JA signalling pathway is involved in rootinduced
responses to larval feeding. Glucosinolate induction cannot fully explain the differences found
in the performance of D. radicum on the different species. Changes in other resistance factors might significantly
contribute to the induced resistance in these brassicaceaeous species as well.