Biocontrol impacts on wheat physiology and Fusarium head blight outcomes are bacterial endophyte strain and cultivar specific

Authors: Whitaker, Briana; Vaughan, Martha; McCormick, Susan

Submitted to: Phytobiomes Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2022
Publication Date: 4/28/2023
Citation: Whitaker, B.K., Vaughan, M.M., McCormick, S.P. 2023. Biocontrol impacts on wheat physiology and Fusarium head blight outcomes are bacterial endophyte strain and cultivar specific. Phytobiomes Journal. 7(1):55-64. https://doi.org/10.1094/PBIOMES-08-22-0056-R.
DOI: https://doi.org/10.1094/PBIOMES-08-22-0056-R

Interpretive Summary: Fusarium head blight (FHB) is a devastating disease of wheat and other cereal crops in the U.S. FHB results in millions of dollars in annual yield losses and results in grain contaminated with a toxin that makes it unsafe to eat. While breeding programs have developed some wheat varieties that are moderately resistant to FHB, farmers currently rely on fungicides to control the disease. Bacteria or other microbes can provide a more environmentally friendly and sustainable way to control crop diseases. However, it wasn’t known if bacteria could effectively control FHB or how the bacteria might otherwise affect the wheat. ARS researchers in Peoria, Illinois, tested seven bacterial strains for control of FHB and measured how treating wheat seed with the bacteria affected the wheat plants. Although the bacteria did not directly compete with or kill the fungus, researchers discovered that the bacteria helped the wheat plants to grow healthier and more robust which made them better able to fight the fungus. This research identified a new, environmentally safe approach to control FHB and provide grain that is safe to eat.

Technical Abstract: Fusarium head blight (FHB) is an economically important disease of small grains globally and is primarily caused by Fusarium graminearum in North America. Recently, microbial biocontrols have risen in importance as sustainable agents of disease control. However, the path to implementation of microbial biocontrols in agriculture will require an understanding of how microbiota impact both plant performance overall and vary with inherent host disease resistance. Using a full-factorial, controlled greenhouse experiment, we tested how seven bacterial endophyte seed soak treatments impacted both plant physiology prior to pathogen infection and FHB disease progression in Triticum aestivum (wheat). Bacterial endophyte treatments strongly impacted the light dependent reactions of photosynthesis, with changes in plant traits regulating light energy allocation and the build-up of electrochemical energy storage across the thylakoid membrane. Physiological responses were contingent on host variety. The direct effects of bacterial endophytes on wheat response to infection were weak and dependent on the inherent disease resistance of the host variety. However, disease outcomes were indirectly mediated by bacterial impacts on plant traits, with some traits emerging as common predictors of disease response across both host varieties (ECSt, vH+) and other traits indicating potential trade-offs in host response to bacterial inoculants (PhiNO, PhiNPQ) and F. graminearum infection. Our results provide an alternate mechanism for microbial biocontrol efficacy other than direct antagonism with the pathogen inside the host. Furthermore, the chlorophyll-fluorescence and absorbance-based markers assessed here may have translational potential as a phenotyping tool for FHB susceptibility in wheat and other small grains.