Vanillin in Resistant Tomato Plant Root Exudate Suppresses Meloidogyne incognita Parasitism

Tomato (Solanum lycopersicum) plants are susceptible to infection by root-knot nematodes, which cause severe economic losses. Planting resistant tomato plants can reduce nematode damage; however, the effects of resistant tomato root exudates in suppressing Meloidogyne incognita remain insufficiently understood. Here, we determined that the resistant tomato plant Lycopersicon esculentum cv. Xianke-8 (XK8) alleviates nematode damage by downregulating the expression of the essential parasitic nematode gene Mi-flp-18 to reduce the infection and reproduction of M. incognita. Using gas chromatography-mass spectrometry, we identified vanillin as a unique compound (compared to susceptible tomato cultivars) in XK8 root exudates that acts as a lethal trap and inhibitor of egg hatching. Moreover, the soil application of 0.4-4.0 mmol/kg vanillin significantly reduced galls and egg masses. The parasite gene Mi-flp-18 was downregulated upon treatment with vanillin, both in vitro and in pot experiments. Collectively, our results reveal an effective nematicidal compound that can use in feasible and economical strategies to control RKNs.