Advances in studies on the chemotaxis of root-knot nematodes

Allelochemical signaling substances released by host roots and rhizosphere microbes play an important role in the host-seeking, mate-searching, and danger escape of root-knot nematodes (RKNs). At present, in order to develop chemoattractants and repellents of plant and microbial sources, it is an international hotspot and frontier for nematologists to identify semiochemicals and related molecular targets in the pre-infection stage of RKNs. This review focused on the chemotaxis and allelochemicals of RKNs, including attractive and repellent compounds, and summarized the progress on Trojan horse mechanism and trapping formation of RKNs. Furthermore, the application of the chemotactic models, including the plate agar and its modified model, Pluronic gel model, and the sand/soil model, on the nematodes chemotaxis test were summarized. Finally, the significance and challenge of the research on RKNs chemotaxis were discussed, and research directions on RKNs chemotaxis in the future were prospected.