Methylorubrum rhodesianumM520 as a biocontrol agent againstMeloidogyne incognita(Tylenchida: Heteroderidae) J2s infecting cucumber roots

Root-knot nematodes (RKNs) are plant pathogens that cause huge economic losses worldwide. The biological management of RKNs may be a sustainable alternative to chemical control methods. Here, the biocontrol potential of Methylorubrum rhodesianum M520 against the RKN Meloidogyne incognita was investigated to theoretically support its application as a biocontrol agent in field production.In-vitro assays showed 91.9% mortality of M. incognita second-stage juveniles in the presence of strain M520 and that the hatching rate of M. incognita eggs was 21.7% lower than that of eggs treated with sterile water. In pot experiments, the M520 treatment caused 70.8% reduction in root-knots and increased plant shoot length and stem and root fresh weights, compared to control plant values. In split-root experiments, cucumber roots treated with M520 showed 25.6% decrease in root gall number, compared to that in control roots.M520 has multiple mechanisms against RKNs and might be used as a biocontrol agent against M. incognita in cucumber, laying a foundation for further studying M520 biocontrol against RKNs.