Microbial Correlates of Fusarium Load and Deoxynivalenol Content in Individual Wheat Kernels

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, pathogen load, deoxynivalenol content, and microbiome profiles for individual wheat kernels collected over 2 years from a disease-conducive environment. We found that the microbiomes of individual, hulled wheat kernels consist of dozens to greater than a hundred bacterial taxa and up to several dozen fungal taxa, and that year-to-year variation in microbiome structure was large. Measures of microbial community diversity were negatively correlated with measures of disease severity, and had significant power to explain variation in pathogen load among seeds. Several operational taxonomic units belonging to the genus Sphingomonas demonstrated particularly strong negative relationships with pathogen load. 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.