Plant-mediated interaction between the root-knot nematode Meloidogyne incognita and the potato aphid Macrosiphum euphorbiae

Plants mediate the interactions between different herbivores that attack simultaneously and sequentially aboveground (AG) and belowground (BG) organs. Local and systemic plant responses underlie such AG-BG herbivore interactions. We investigated the impact of root infection by the root-knot nematode Meloidogyne incognita, at different infection cycle stages, on tomato leaf responses triggered by the aphid Macrosiphum euphorbiae. We further analyzed the reverse impact of aphid leaf feeding on the root responses triggered by M. incognita. We found that M. incognita root infection impeded systemically the repression of the steroidal glycoalkaloids related responses mediated in leaves by the aphids. By contrast, aphid feeding did not systemically alter the defense responses triggered by M. incognita in roots. We demonstrate an asymmetrical interaction between M. incognita and Ma. euphorbiae when co-occurring in tomato plants, where M. incognita infection determines the root defense status, regardless of AG feeding by Ma. euphorbiae. Keywords: Phytohormones, plant-mediated interactions, potato aphid (Macrosiphum euphorbiae), root-knot nematodes (Meloidogyne incognita), systemic responses, local response