Enhancement of Actinobacteriota and suppression of root-knot nematode infection in cucumbers through chitin application

Abstract

Abstract Background and Aims: Root-knot nematodes (Meloidogyne spp.) are endoparasitic plant pathogens. The infection seriously reduces the yield and quality of crops and frequently causes continuous cropping obstacles to facility cultivation. Biological control methods have been used to restrict root-knot nematodes, such as the application of crustacean shell powder, which is proposed to increase of chitinolytic bacteria, especially those belonging to Actinobacteriota. However, its influences to soil microbiome remain largely unknown. Methods: We used targeted metagenomics to investigate the changes in soil bacterial community for root-knot nematode-infected cucumber (Cucumis sativus L.) treated by crustacean shell powder with a pot system. Results: The chitin application significantly increased the relative abundances of Firmicutes and Actinobacteriota and reduced the symptoms caused by root-knot nematodes with a dose-dependent manner. Functional prediction suggested that these bacteria may improve chitin hydrolysis and nitrification in the soil, leading to inhibition of root-knot nematodes and growth promotion of cucumbers. On the contrary, the treatment of Streptomyces was less effective than the chitin application as they hardly colonize in the pot system. Conclusion: Chitin application may introduce chitinolytic bacteria and enhance soil nitrification to alleviate the infection of root-knot nematodes and stimulate plant growth.