Biological control of Sclerotinia sclerotiorum: Modes of action of biocontrol agents, soil organic amendments, and soil microbiome manipulation

Biological control using antagonistic microorganisms as biological control agents (BCAs) has been considered a potential environmentally-friendly alternative or supplement for the control of soil-borne plant pathogens. This may be part of an integrated disease management system, thus contributing to a reduction in the use of chemical products and the protection of the environment. This review aims to provide an updated overview and insight into the underlying antagonistic mechanisms of BCAs to directly or indirectly suppress Sclerotinia sclerotiorum, an economically devastating soil-borne fungal pathogen of a broad range of plants. Further, the application of organic amendments (OAs) has demonstrated the potential to suppress soil-borne plant pathogens through the introduction of BCAs to the soil and/or enhancing the activity of the existing soil microbiome and BCAs which improves general plant health. Therefore, the manipulation and exploitation of soil microbial communities, through the application of OAs, has the potential as part of a sustainable integrated disease management strategy for the control of soil-borne plant pathogens, particularly S. sclerotiorum. In this review, we highlight gaps in the current understanding of the interaction of BCAs, OAs, and S. sclerotiorum and suggest future directions for research in this space, including improving our understanding of the microbiomes of soils and OAs suppressive to S. sclerotiorum.