Bt Research 2024, Vol.15, No.3, 110-117 http://microbescipublisher.com/index.php/bt 111 nematode infection (Yin et al., 2021). These findings underscore the potential of Bacillus spp. as biocontrol agents and pave the way for their application in integrated pest management (IPM) strategies against M. enterolobii. This review paper aims to explore the integration of Bacillus spp. into IPM strategies for the control of M. enterolobii. By examining the current state of research, we will assess the viability of these biological control agents and discuss their potential role in sustainable agriculture. The need for innovative and environmentally conscious approaches to pest management has never been greater, and Bacillus spp. may hold the key to safeguarding crop production against the pervasive threat of M. enterolobii. 2Bacillus spp. as Biocontrol Agents 2.1 General characteristics of Bacillus spp. that contribute to their biocontrol potential Bacillus species are well-recognized for their biocontrol potential, primarily due to their ability to produce a wide array of antimicrobial compounds. These compounds are effective against various plant pathogens, including fungi, bacteria, and nematodes. The biocontrol efficacy of Bacillus spp. is also attributed to their capacity to form endospores, which are highly resistant to environmental stresses, allowing them to survive in adverse conditions. This resilience facilitates their persistence in the soil and rhizosphere, providing long-term protection for plants against pathogens. Additionally, Bacillus spp. can promote plant growth by producing phytohormones and facilitating nutrient uptake, which indirectly enhances plant defense mechanisms against pests and diseases. 2.2 Historical perspective on the use of Bacillus spp. in biocontrol The use of Bacillus spp. as biocontrol agents has a rich history, with early reports dating back to the 20th century. Initially, the focus was on Bacillus thuringiensis due to its insecticidal properties, but over time, other Bacillus species have been explored for their nematicidal capabilities. For instance, Bacillus cereus has been identified as a potent biocontrol agent against root-knot nematodes, such as Meloidogyne incognita. Studies have shown that certain strains of B. cereus can cause significant mortality of nematode juveniles and reduce egg hatching rates, as well as form biofilms on plant roots, which protect the plants from nematode infection (Yin et al., 2021). The historical progression in the use of Bacillus spp. reflects a growing interest in sustainable and environmentally friendly pest management strategies, which are crucial in the face of increasing resistance to chemical nematicides and the need to preserve soil health. 3 Mechanisms of Action of Bacillus spp. against Meloidogyne spp. 3.1 Overview of the direct antagonistic capabilities of Bacillus spp. Bacillus spp. have demonstrated significant direct antagonistic capabilities against Meloidogyne spp., particularly Meloidogyne incognita. Studies have shown that certain strains of Bacillus, such as B. firmus I-1582, can directly manage nematode populations by increasing mortality rates of second-stage juveniles (J2s) to above 75%(Gattoni et al., 2023). Similarly, B. cereus strain S2 has been found to cause high mortality rates in M. incognita, with the production of nematicidal compounds like sphingosine contributing to this effect (Gao et al., 2016). Another strain, B. cereus Bc-cm103, has been reported to cause 100% mortality of J2s within 12 hours and to decrease egg hatching rates (Yin et al., 2021). These findings indicate that Bacillus spp. can directly antagonize Meloidogyne spp. through the production of bioactive metabolites and other mechanisms. 3.2 Systemic resistance induced by Bacillus spp. and its role in plant defense Bacillus spp. are not only capable of direct antagonism but also play a crucial role in inducing systemic resistance within host plants. B. amyloliquefaciens QST713 and B. firmus I-1582 have been shown to stimulate systemic resistance in plants, leading to the upregulation of defense-related genes (Gattoni et al., 2023). B. cereus S2 has also been reported to induce systemic resistance in tomato plants, enhancing the activity of defense-related enzymes (Gao et al., 2016). Furthermore, B. firmus I-1582 has been found to induce systemic resistance in tomato plants, with the dynamic regulation of genes related to the salicylic acid (SA) and jasmonic acid (JA) pathways (Ghahremani et al., 2020).
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