Induced defense response in tomato roots by root-knot nematode infestation at different life cycle stages and aboveground insect herbivory

Our study aim was to analyze the impact of aboveground herbivores on root defense responses triggered by root feeding nematodes at different stages of their lifecycle. We investigated changes in phytohormone and α-tomatine levels, as well as the expression of defense signaling markers and glycoalkaloids metabolism (GAME) genes in roots of Solanum lycopersicum (tomato). The tomato plants were infested with root-knot nematode for 5, 15 or 30 days before being challenged with larvae of Spodoptera exigua aboveground. We collected root material after 24 h of aboveground feeding for molecular and biochemical analysis. Our results show that when root-knot nematodes and S. exigua co-occur on tomato plants, S. exigua herbivory might affect JA-regulated root defense responses induced by root-knot nematodes when the nematodes start to reproduce (30 days post infestation).