Microbial correlates of Fusarium load and deoxynivalenol content in individual wheat kernels

Authors: Bakker, Matthew; McCormick, Susan

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2019
Publication Date: 5/8/2019
Citation: Bakker, M.G., McCormick, S.P. 2019. Microbial correlates of Fusarium load and deoxynivalenol content in individual wheat kernels. Phytopathology. https://doi.org/10.1094/PHYTO-08-18-0310-R.
DOI: https://doi.org/10.1094/PHYTO-08-18-0310-R

Interpretive Summary: Fusarium head blight is a damaging disease that limits the productivity and profitability of wheat crops. Because the fungus that causes this disease produces toxic chemical compounds (mycotoxins) that can accumulate in the grain, there is also a food safety hazard that results from this plant disease. In addition to the pathogen causing Fusarium head blight, wheat plants are also colonized by a diverse mixture of other micro-organisms, collectively referred to as the microbiome. Interactions between Fusarium and other components of the microbiome may be important in determining the rates at which infection spreads or mycotoxins accumulate. To explore such relationships, we measured the amount of Fusarium, the concentration of mycotoxins, and the makeup of the microbiome associated with each of more than 200 kernels of wheat. Connections between these variables suggest possibilities for new approaches to limiting the severity of Fusarium head blight.

Technical Abstract: Characteristics or constituents of plant-associated microbiomes may assist in constraining disease development. To investigate this possibility for the wheat-Fusarium head blight pathosystem, we assessed seed weight, Fusarium graminearum load, deoxynivalenol content, and microbiome profiles for individual wheat kernels collected over two years from a disease-conducive environment. Relationships among these variables suggest that microbiome characteristics (apart from pathogen load) make a small contribution to explaining disease components within individual kernels. We find that the microbiomes of individual, hulled wheat kernels consist of dozens to hundreds of bacterial taxa and up to several dozen fungal taxa. Year-to-year variation in microbiome structure was large, but the relative abundance of several taxa (notably, Sphingomonas spp.) varied with pathogen load. Many fungal taxa also differed in relative abundance between seeds with vs. without measurable deoxynivalenol content. Greater similarity among communities from the same vs. from different heads suggest a biographic structuring of bacterial communities that was not mirrored among fungal communities. This study illuminates the composition of microbiomes associated with wheat kernels under disease-conducive field conditions, and suggests relationships between microbiome characteristics and Fusarium head blight that warrant further study.