Bt Research 2024, Vol.15, No.3, 110-117 http://microbescipublisher.com/index.php/bt 114 Bacillus amyloliquefaciens Y1 produces the dipeptide cyclo (d-Pro-l-Leu), which has been identified for the first time as having nematocidal activity. This strain significantly reduces the count of eggs and galls on tomato plant roots and enhances plant growth parameters (Jamal et al., 2017). Two strains of Bacillus thuringiensis, LBIT-596 and LBIT-107, have been characterized for their nematicidal activity. These strains produce spore-crystal complexes that are lethal to nematodes and have shown to decrease the number of galls caused byM. incognita in tomato plants (Verduzco-Rosas et al., 2021). Bacillus subtilis strain Bs-1, isolated from rhizospheric soil, has strong nematicidal effects, causing egg hatching inhibition and repellence of M. incognita. This strain has been effective in reducing root galls and promoting the growth of cucumber in both pot and field experiments (Cao et al., 2019). The efficacy of Bacillus cereus strain Bc-cm103 against M. incognita has been confirmed in pot, split-root, and field tests, where it significantly reduced the appearance of root galls. The strain also activates defense-responsive genes in cucumber (Yin et al., 2021). Bacillus aryabhattai MCCC 1K02966, a deep-sea bacterium, has shown nematicidal and fumigant activities against M. incognita. The VOC methyl thioacetate produced by this strain exhibits multiple nematicidal activities, including contact nematicidal, fumigant, and repellent activities (Chen et al., 2021). Native Bacillus thuringiensis strains have been investigated for their potential against M. incognita. Certain strains have been found to inhibit juvenile emergence and exhibit biocontrol potential by suppressing nematode reproduction in tomato plants (Ramalakshmi et al., 2020). Lastly, the purL gene of Bacillus subtilis has been associated with nematicidal activity. Strains OKB105 and 69 have been used to treat various nematodes, with high mortality rates observed, indicating the potential role of the purLgene in nematicidal activity (Xia et al., 2011). In conclusion, Bacillus spp. offer a diverse arsenal of biological control agents against M. incognita, with various strains producing different nematicidal compounds and mechanisms. These findings support the integration of Bacillus-based biocontrol strategies into pest management programs for sustainable agriculture. 6 Challenges and Limitations The integration of Bacillus spp. into pest management strategies, particularly for controlling the aggressive Meloidogyne enterolobii, presents a promising avenue. However, several challenges and limitations still need to be addressed to optimize their effectiveness and ensure sustainable use. 6.1 Limitations in the current understanding of Bacillus spp. mechanisms of action While Bacillus spp. are known to exert nematicidal effects, the detailed mechanisms underlying these interactions remain inadequately characterized. Several strains, such as Bacillus thuringiensis and Bacillus subtilis, have demonstrated potential in secreting bioactive compounds that affect nematodes adversely. These compounds include enzymes, toxins, and various secondary metabolites which can disrupt the nematode's cuticle, affect its digestive system, or impede its neural functions. However, the specific pathways and the molecular targets of these bioactive substances in nematodes are not fully elucidated. This gap in knowledge hampers the ability to predict and enhance the effectiveness of Bacillus-based formulations against specific nematode pests like Meloidogyne enterolobii. 6.2 Challenges in the application and consistency of Bacillus spp. as biocontrol agents The application of Bacillus-based biocontrol agents in the field faces several practical challenges. First, the environmental persistence and activity of Bacillus spores can be highly variable, influenced by soil type, moisture, temperature, and the presence of other microorganisms. These factors can lead to inconsistent results in field applications, where efficacy might not replicate the success seen in controlled, laboratory conditions. Moreover, the formulation of Bacillus products needs to ensure that the bacterial spores remain viable and capable of
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