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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #399962
Research Project: Genetic Improvement and Cropping Systems of Alfalfa for Livestock Utilization, Environmental Protection and Soil Health

Location: Plant Science Research

Title: Surfactin and Spo0A-dependent antagonism by bacillus subtilis strain UD1022 against medicago sativa phytopathogens

Author
item ROSIER, AMANDA - University Of Delaware
item POMERLEAU, MAUDE - Universite De Sherbrooke
item BEAUREGARD, PASCALE - Universite De Sherbrooke
item Samac, Deborah - Debby
item BAIS, HARSH - University Of Delaware

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2023
Publication Date: 2/23/2023
Citation: Rosier, A., Pomerleau, M., Beauregard, P.B., Samac, D.A., Bais, H.P. 2023. Surfactin and Spo0A-dependent antagonism by bacillus subtilis strain UD1022 against medicago sativa phytopathogens. Plants. 12(5). Article 1007. https://doi.org/10.3390/plants12051007.
DOI: https://doi.org/10.3390/plants12051007

Interpretive Summary: Alfalfa is susceptible to a wide range of diseases that result in losses of crop yield and nutrient value. Most of the diseases are not controlled by chemical treatments because of cost or the lack of effective chemistries. Plant growth promoting bacteria may be ideal natural alternatives to chemical crop treatments because of their wide range in activity. One bacterial strain, Bacillus subtilis UD1022 was tested for activity against important alfalfa pathogens. The strain had potent antagonistic activity against two foliar pathogens and a root rot pathogen on culture plates, but not a wilt pathogen. Activity against a foliar pathogen causing anthracnose was likely due to production of the antibiotic surfactin. Activity against the root rot pathogen was through production of biofilms. The results indicate that UD1022 would be a good candidate for providing broad disease control under field conditions.

Technical Abstract: Plant growth promoting rhizobacteria (PGPR) such as the soil and root colonizer Bacillus spp. may be ideal natural alternatives to chemical crop treatments. The PGPR Bacillus subtilis UD1022 has robust plant protective and growth promotional activities in a wide range of model and horticultural plant species. This work seeks to extend the application of the PGPR UD1022 to Medicago sativa (alfalfa) forage crop production. Alfalfa is important as a high-protein legume supporting the dairy industry and for sustainable agriculture practices due to its symbiosis with nitrogen fixing bacteria. However, alfalfa can be susceptible to a wide range of phytopathogens that result in losses of crop yield and nutrient value. To determine if UD1022 antagonizes alfalfa phytopathogen growth, the bacterium and pathogen strains were cultured together on petri plates directly or in separate compartments. We found UD1022 to be directly antagonistic toward Collectotrichum trifolii, Ascochyta medicaginicola (formerly Phoma medicaginis), and Phytophthora medicaginis. Using mutant strains, UD1022 antagonism toward the ascomycete A. medicaginicola StC 306-5 is likely to be influenced by secondary metabolites such as the non-ribosomal peptide antibiotic surfactin. Antagonism toward Phytophthora medicaginis A2A1 was not affected by secondary metabolites but was dependent on B. subtilis biofilm pathway components. The B. subtilis central regulator spo0A, gene was required for the antagonism for both phytopathogens, but likely through different mechanisms (antibiotic versus biofilm). The results of these antagonism assays indicate that the PGPR UD1022 would be a good candidate for further investigations into its antagonistic activities in plant and field studies.