Bacterial community assembly in wheat phyllosphere. Leaf bacteria community assembly and its response to flooding is controlled by plant phenology in wheat (Triticum aestivum L.)

Leaf microbiota mediate foliar functional traits, influence plant fitness, and contribute to several ecosystem functions, including nutrient and water cycling. Plant phenology and harsh environmental conditions have been described as the main determinants of leaf microbiota assembly. Yet, we still have a limited understanding of the effect of extreme weather events on the composition and functions of the microbes inhabiting the phyllosphere. Here, we established a pot experiment to determine the effects of flooding stress on the wheat leaf microbiota. Since plant phenology might be an important factor in the response to hydrological stress, flooding was induced at different plant growth stages (tillering, booting and flowering). Using a metabarcoding approach we monitored the response of leaf bacterial to flooding, while key soil and plant traits were measured to correlate physiological plant and edaphic factor changes with shifts in the bacterial leaf microbiota assembly. In our study, plant growth stage represented the main driver in leaf microbiota composition, as early and late plants showed distinct bacterial communities. Interestingly, flooding had a differential effect on leaf microbiota dynamics depending at which developmental stage it was induced, as a more pronounced disruption in community assembly was observed in younger plants.