Isolation and Screening of Bacterial Strains

We followed the method described by Wang et al. (2021) to isolate the soil bacteria. Rhizosphere soil in which healthy tomato (Lycopersicon esculentum) plants grew was collected from areas infested with tomato root-knot nematode disease. Soil samples (5 g) were suspended in 50 ml of sterile distilled water and mixed on a table concentrator for 30 min. These soil samples were serially diluted (up to 10^–7-fold), plated on potato dextrose agar (PDA), and incubated at 30 ± 2°C for 2–3 days. Bacterial colonies growing on the plates were isolated according to their morphological characteristics for further study. Subsequently, the isolated strains were screened using in vitro tests, for which purpose, they were transferred to an LB solid medium plate. After activation at 30°C, purified single colonies were picked using a sterile inoculating loop and placed in a 250 ml conical flask containing 50 ml LB liquid medium. After 24 h of cultivation at 30°C, with stirring at 200 rpm, the inoculum was connected to the 50 ml LB culture medium at a ratio of 2% and cultured at 30°C and 200 rpm in a 250 ml conical flask for 48 h to prepare a fermentation broth. This broth was then centrifuged at 13,000 rpm for 10 min and filtered through a 0.22 μm sterile syringe filter. Lastly, 0.8 ml of the filtrates was placed in 1.5 ml centrifuge tubes before adding 100 s-stage juveniles (J2s) of M. incognita to each centrifuge tube. The corrected mortality of the J2s of M. incognita was calculated at 24 h and again at 48 h. Each treatment was repeated six times.