The role of Bacillus species in the management of plant-parasitic nematodes

Abstract

Plant-parasitic nematodes (PPNs), including root-knot nematodes (Meloidogyne spp.), cyst nematodes (Heterodera and Globodera spp.), and other economically significant nematode species, pose severe threats to global agriculture. These nematodes employ diverse survival strategies, such as dormancy in cysts or robust infective juvenile stages. Consequently, their management is challenging. Traditional control methods, such as the use of chemical nematicides, are increasingly scrutinized because of environmental and health concerns. This review focuses on the specific mechanisms employed by Bacillus spp., including nematicidal compound production, systemic resistance induction, and cuticle degradation, to target root-knot and cyst nematodes. These mechanisms offer sustainable solutions for managing nematodes and promoting soil health by enhancing microbial diversity and nutrient cycling. An integrated approach leveraging Bacillus-based biocontrol is proposed to maximize efficacy and agricultural sustainability.

Keywords: Bacillus spp.; biocontrol; integrated pest management; nematicidal compounds; plant-parasitic nematodes.

Figure 1

Schematic representation of comparison of conventional and Bacillus-based nematode management strategies.

Figure 2

Mode of action of Bacillus spp. against plant-parasitic nematodes. The figure illustrates the sequential mechanisms of Bacillus species, including the entry of spores into the nematode body via ingestion or adhesion to the cuticle, enzymatic degradation of structural components (such as cuticles and eggshells), and disruption of intestinal cells through Cry and Cyt toxin-induced pore formation. The figure also highlights the inhibition of nematode reproduction, the disruption of cellular metabolism, and systemic physiological collapse, ultimately resulting in nematode mortality.

Figure 3

Timeline of Bacillus species development as biocontrol agents. This timeline highlights significant milestones in the development of Bacillus species as biocontrol agents, from their initial discovery to advancements in genetic engineering and sustainable agricultural practices.

Figure 4

Major Bacillus species and their diverse array of proteins and secondary metabolites against the plant-parasitic nematodes. Information adapted from [1] Kahn et al. (2021), [2] Ghahremani et al. (2020), [3] Kulkova et al. (2023), [4] Niu et al. (2006), [5] Jamal et al. (2017), [6] Manju and Subramanian, 2017, and [7] Hu et al. (2022).

Figure 5

Graphical representation of how the application of Bacillus strains as soil amendments alone or in combination with organic matter enhances soil health and structure and reduces nematode proliferation through several interrelated mechanisms.

Figure 6

Graphical representation of how seed treatment with Bacillus spp. enhances plant growth, improves soil health, and reduces nematode populations.

Figure 7

Graphical representation of integrated pest management strategies using Bacillus strains for nematode control.