The microbiome of cereal plants: The current state of knowledge and the potential for future applications

The plant microbiota fulfils various crucial functions related to host health, fitness, and productivity. Over the past years, the number of plant microbiome studies continued to steadily increase. Technological advancements not only allow us to produce constantly increasing datasets, but also to extract more information from them in order to advance our understanding of plant-microbe interactions. The growing knowledge base has an enormous potential to improve microbiome-based, sustainable agricultural practices, which are currently poorly understood and have yet to be further developed. Cereal plants are staple foods for a large proportion of the world's population and are therefore often implemented in microbiome studies. In the present review, we conducted extensive literature research to reflect the current state of knowledge in terms of the microbiome of the four most commonly cultivated cereal plants. We found that currently the majority of available studies are targeting the wheat microbiome, which is closely followed by studies on maize and rice. There is a substantial gap, in terms of published studies, addressing the barley microbiome. Overall, the focus of most microbiome studies on cereal plants is on the below-ground microbial communities, and there is more research on bacteria than on fungi and archaea. A meta-analysis conducted in the frame of this review highlights microbiome similarities across different cereal plants. Our review also provides an outlook on how the plant microbiota could be harnessed to improve sustainability of cereal crop production.