Evaluation of Virgibacillus dokdonensis MCCC 1A00493 as a biological control agent and microbial organic fertilizer against root-knot nematodes

Root-knot nematodes (RKNs) can result in severe losses to crop production and economies. Virgibacillus dokdonensis MCCC 1A00493, a deep-sea bacterium, has demonstrated potent antagonistic effects against Meloidogyne incognita in vitro. However, the control efficacy under greenhouse and field conditions remains unclear. In this study, we investigated the nematicidal effect of MCCC 1A00493 fermentation liquid and its synergism with black soldier fly (BSF) larval frass organic fertilizer both in greenhouse and field experiments. MCCC 1A00493 fermentation liquid demonstrated a significant control efficacy on RKNs both in greenhouse and field experiments, with the highest control efficacy reaching 68.97 % and 74.87 %, respectively. Meanwhile, the synergistic effects of MCCC 1A00493 and BSF larvae frass organic fertilizer was investigated by adding 10 % suspension (1 × 10⁹ CFU/mL) of MCCC 1A00493 into 71.51 kg of chicken manure organic fertilizer produced by co-conversion of BSF larvae and Bacillus subtilis BSF-CL. It was noted that MCCC 1A00493 microbial organic fertilizer reduced disease incidence of RKNs significantly both in greenhouse and field experiments, with the root gall index decreasing by 51.75 % and 63.22 %, respectively. MCCC 1A00493 fermentation liquid and microbial organic fertilizer demonstrated a control efficacy on RKNs exceeded commercial nematicide avermectin and commercial bio-organic fertilizer, respectively. In addition, MCCC 1A00493 fermentation liquid and microbial organic fertilizer had positive effects on the growth of tomato plants. These findings confirmed that V.dokdonensis MCCC 1A00493 as a biological control agent and microbial organic fertilizer have significant effect on RKNs and can be used as potential biocontrol preparations.