Bacillus velezensis RKN1111 enhances resistance against Meloidogyne incognita in Cucumis sativus.

Abstract

Background: Meloidogyne incognita is a highly damaging pathogenic nematode that causes significant annual economic losses. Therefore, the development of reliable biological control agents against M. incognita is imperative. The Bacillus velezensis RKN1111 strain, isolated from inter-root soil, demonstrates the ability to directly kill M. incognita. In this study, we investigated the effect of RKN1111 in inducing resistance to M. incognita in Cucumis sativus and examined changes in the content of immune-responsive substances in the induction-treated cucumber plants.

Result: The RKN1111 treatment reduced the number of root galls in infected cucumbers, with a maximum reduction of 78.19%. RKN1111 stably colonized cucumber roots, reaching 3.65 × 10⁶ CFU/g in 3 days. The approach and infestation rates of M. incognita on RKN1111-induced treated cucumber root tips declined at varying time points. Furthermore, RKN1111 induced significant increases (P < 0.05) in hydrogen peroxide (H₂O₂) and superoxide anion (O^2-) contents, as well as in the callose deposition area in cucumber, by up to 59.84, 83.28, and 61.59%, respectively.

Conclusion: RKN1111 has been demonstrated to stably colonize cucumber root systems and defend against M. incognita infestation by inducing systemic resistance in the host plant. Additionally, RKN1111 elevated the levels of immune-responsive substances in cucumber plants. RKN1111 has great potential for application in the integrated pest management of M. incognita. © 2025 Society of Chemical Industry.