Bacillus-based bionematicides: development, modes of action and commercialisation

ABSTRACT

Agricultural crops are severely damaged by root-knot nematodes causing extensive financial losses globally. Historically, agrochemicals have been the preferred method to combat these pests; however, threats to humans and the environment posed by these agrochemicals led to the need for developing new biocontrol agents. Importantly, the latter should adhere to biosafety regulations while being highly effective. Root-knot nematodes live in soil and thus the use of rhizobacteria such as Bacillus for biocontrol development have shown potential. Although various Bacillus species have been tested in this capacity, little is known about their secondary metabolites and the mechanisms of action responsible for their nematicidal activity. If these secondary metabolites can be qualitatively and quantitatively characterised, metabolic features could be synthetically engineered and used to combat root-knot nematodes. Although there is great potential for bionematicides, the commercialisation and development of such products can be difficult. This review summarises the importance of Bacillus species as natural antagonists of root-knot nematodes through the production of secondary metabolites. It provides an overview of the significance of root-knot nematodes in agriculture and the advances of chemical nematicides in recent years. The potential of Bacillus species as biocontrol agents, the known mechanisms of action responsible for the nematicidal activity demonstrated by Bacillus species, non-target effects of biocontrol agents and the commercialisation of Bacillus-based bionematicides are discussed.

KEYWORDS:

• Bacillus
• biocontrol
• Meloidogyne incognita
• plant growth-promoting rhizobacteria
• root-knot nematode
• secondary metabolites

Acknowledgements

Opinions expressed and conclusions arrived at, are those of the authors and are not necessarily to be attributed to the NRF.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Sarina Claassens http://orcid.org/0000-0003-3955-4361

Additional information

Funding

The financial support of the National Research Foundation (NRF), South Africa, as bursaries to GE [grant number 106783] and IH [grant number 111891], are hereby acknowledged.