Plant growth-promoting bacteria inhibit fungal plant pathogens

Climate change brings severe agricultural challenges as crops are exposed to increased levels of both abiotic (drought, waterlogging) and biotic stresses (fungal diseases). A large body of literature now shows that by enriching soils with bacteria possessing plant growth-promoting (PGP) characteristics, plant resilience against pathogens can be improved. However, to identify beneficial bacteria, it is important to first investigate their PGP potential. Here, we assessed the PGP potential of selected (novel) soil bacteria of local (UK) and global origin, including Pseudomonas, Mucilaginibacter, and Paenibacillus species. Employed approaches included assessment of the production of PGP metabolites, solubilisation of (in)organic compounds, enzyme activity, tolerance of stressors, biofilm formation, and nitrogen fixation. We found that all investigated bacteria possess some but not all of the PGP properties. Ps. protegens DTU 9.1, Ps. koreensis C63, and Ps. koreensis D70 showed the greatest PGP potential while M. gossypiicola and M. frigoritolerans were the least active. Subsequently, we assessed the potential of these bacteria to inhibit the growth of several different fungal pathogens (Botrytis cinerea, Ramularia collo-cygni, and Zymoseptoria tritici). We found that a majority of bacteria were able to inhibit the growth of at least one of the fungal pathogens. Analysis of genomic sequencing data suggests that some of these bacteria produce novel antifungal compounds. We are currently working to purify and identify these novel antifungal compounds, and to test the bacteria’s potential to be used in biocontrol strategies to prevent and treat plant diseases.