Bt Research 2024, Vol.15, No.3, 110-117 http://microbescipublisher.com/index.php/bt 113 4.2 Case study 2: biocontrol of Meloidogyne sp. on tomato plants by selectedBacillus spp. Integrated Pest Management (IPM) strategies are crucial for sustainable agriculture, and the use of biocontrol agents, such as Bacillus spp., has gained attention for their potential to control plant-parasitic nematodes like Meloidogyne spp. This case focuses on the efficacy of selected Bacillus strains in suppressing Meloidogyne spp. on tomato plants. Research has shown that individual Bacillus strains can significantly reduce the infestation of Meloidogyne incognita on tomato roots. Strains BMH and INV, closely related to Bacillus velezensis, were individually capable of reducing the number of galls and eggs by more than 90% (Cruz-Magalhães et al., 2021). However, when these strains were combined, the suppression of M. incognita and the promotion of tomato shoot weight were not as effective as when applied separately (Cruz-Magalhães et al., 2021). This suggests that while individual strains have strong biocontrol potential, their combination does not necessarily enhance their biocontrol activity. Another study evaluated a dual-strain combination of B. paralicheniformis FMCH001 and B. subtilis FMCH002, which exhibited nematicidal properties in the pre-infection phase. This combination decreased egg hatching, juvenile survival, and attractiveness to the roots of tomato plants. Moreover, it impaired nematode establishment, gall formation, and giant cell development, indicating interference with the nematode's Morphogenetic mechanisms (Díaz-Manzano et al., 2023). The dual-strain combination also effectively reduced nematode reproduction, regardless of the application mode, and was effective against other plant-parasitic nematodes and in different crops (Díaz-Manzano et al., 2023). Furthermore, other Bacillus spp. have been identified as effective biocontrol agents against Meloidogyne spp., enhancing the growth and yield of tomato plants. These strains not only reduced the number of galls, egg masses, and nematodes in the soil but also promoted plant growth and yield, offering an alternative to chemical nematicides (Habazar et al., 2021). Although chemical treatments were more effective in controlling nematode populations, Bacillus spp. provided the added benefit of promoting plant health (Habazar et al., 2021). It can be seen from this case study that Bacillus spp. offer a promising alternative for the biocontrol of Meloidogyne spp. in tomato plants. While individual strains have shown significant biocontrol potential, the effectiveness of strain combinations may vary. The multifunctional nature of Bacillus spp., including their role as plant growth promoters, makes them an integral part of IPM strategies for sustainable agriculture (Cruz-Magalhães et al., 2021; Habazar et al., 2021; Díaz-Manzano et al., 2023). 5 Overview of Bacillus strains with Nematicidal Activity The genus Bacillus has been recognized for its role in the biological control of plant-parasitic nematodes, particularly Meloidogyne incognita. Several Bacillus strains have been identified to possess nematicidal properties, offering a sustainable alternative to chemical nematicides. Bacillus cereus strain S2 has been reported to exhibit high nematicidal activity against M. incognita, with mortality rates reaching up to 90.96% in laboratory conditions. The strain produces sphingosine, a compound that has been identified as lethal to nematodes, and has shown to induce systemic resistance in tomato plants (Gao et al., 2016). Another strain, Bacillus firmus YBf-10, has demonstrated systemic nematicidal activity, reducing nematode damage in tomato plants and promoting plant growth. The biocontrol efficacy of this strain is attributed to its secondary metabolites (Xiong et al., 2015). Bacillus cereus strain Bc-cm103 has been used as a biological control agent due to its production of volatile organic compounds (VOCs) that exhibit fumigation activity against M. incognita. The VOCs produced by Bc-cm103, including dimethyl disulfide, have shown high mortality rates in nematodes (Yin et al., 2020).
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