Bacillus subtilis for plant health and crop yield improvements:

The huge range benefits of applying Bacillus subtilis for plant health and crop yield improvements:  

Introduction:

Plant diseases are a major concern for agriculture, and traditional methods of disease control are often associated with adverse environmental and health effects. The use of beneficial bacteria, such as Bacillus subtilis, has been suggested as a promising alternative approach to plant disease control. Bacillus subtilis can colonize plant surfaces and produce antimicrobial compounds that suppress the growth and development of plant pathogens.

Modes of action:

Bacillus subtilis produces a range of secondary metabolites that contribute to its efficacy against plant pathogens. These include antibiotics, such as bacillomycin and iturin, which have broad-spectrum antimicrobial activity against a range of plant pathogens, including fungi, bacteria, and nematodes. Bacillus subtilis also produces siderophores, which are iron-chelating compounds that limit the availability of iron to pathogenic microorganisms. Moreover, Bacillus subtilis can produce enzymes, such as chitinases and glucanases, which can degrade pathogen cell walls and membranes.

Efficacy against plant diseases:

Bacillus subtilis has been shown to be effective against a range of plant diseases. For instance, a study conducted on tomato plants infected with Fusarium oxysporum showed that the application of Bacillus subtilis reduced disease incidence by 70% (Liu et al., 2017). Similarly, the application of Bacillus subtilis has been shown to be effective against powdery mildew in cucumbers (Wu et al., 2019), bacterial wilt in tomato plants (Ghazijahani et al., 2019), and gray mold in strawberries (Zhang et al., 2018).

Efficacy against plant pests:

There is also published research on the efficacy of Bacillus subtilis in controlling pest insects and arthropods such as slugs and snails.

One study found that Bacillus subtilis strains were effective in reducing the number of whiteflies and aphids on tomato plants in greenhouse experiments (Benitez et al., 2017). Another study showed that the application of Bacillus subtilis reduced the populations of thrips and mites on pepper plants in a greenhouse setting (Zhang et al., 2017).

Moreover, there is evidence that Bacillus subtilis can control slugs and snails. A study found that the application of Bacillus subtilis spores reduced the number of slug and snail eggs and increased seedling survival in a field experiment (Kok et al., 2017).

Effects on plant growth and development:

In addition to its efficacy against plant pathogens, Bacillus subtilis has been shown to have positive effects on plant growth and development. Bacillus subtilis can produce plant growth-promoting compounds, such as auxins, cytokinins, and gibberellins, which can stimulate plant growth and development. Moreover, Bacillus subtilis can also induce systemic resistance in plants, which enhances their natural defense mechanisms against pathogens. For example, the application of Bacillus subtilis has been shown to increase the activity of plant defense enzymes, such as peroxidase and polyphenol oxidase, in cucumber plants (Wu et al., 2019).

Improving efficacy in combination with other biological agents:

Bacillus subtilis can be used in combination with other biological control agents to enhance its efficacy against plant pathogens. For instance, the combined application of Bacillus subtilis and Trichoderma asperellum has been shown to be more effective than either agent alone against Fusarium wilt in tomato plants (Liu et al., 2017). Similarly, the combined application of Bacillus subtilis and Pseudomonas fluorescens has been shown to be more effective against powdery mildew in cucumbers (Gao et al., 2019) than B.subtilis on its own. Moreover, the combined application of Bacillus subtilis and mycorrhizal fungi has been shown to increase plant growth and enhance resistance against various plant diseases (Khalifa et al., 2016).

The use of multiple biological control agents can provide several benefits. Firstly, it can increase the diversity of antimicrobial compounds produced, which can enhance the spectrum of activity against a range of plant pathogens. Secondly, it can lead to synergistic effects, where the combination of two or more biological control agents produces a greater effect than the sum of their individual effects. Finally, the use of multiple biological control agents can reduce the likelihood of developing pathogen resistance, as it is less likely that a pathogen will develop resistance to multiple antimicrobial compounds.

However, the use of multiple biological control agents can also pose some challenges. Firstly, it can be difficult to find compatible biological control agents, as some agents may compete with each other for resources or produce antagonistic effects. At Biologix we have tested many different microbial products over the years to discover the combinations that achieve the best results. 

Bacillus subtilis is one of the key beneficial microbial species we add across all of the Biologix range of products.