The study of plant-microbe associations by new techniques has significantly improved our understanding of the structure and specificity of the plant microbiome. Yet, microbiome function and the importance of the plant’s microbiome in the context of human and plant health are largely unexplored. Comparable with our human microbiome, millions of microbes inhabit plants, forming complex ecological communities that influence plant growth and health through its collective metabolic activities and host interactions. Viewing the microbiota from an ecological perspective can provide insight into how to promote plant health and stress tolerance of their hosts or how to adapt to a changing climate by targeting this microbial community. Moreover, the plant microbiome has a substantial impact on human health by influencing our gut microbiome by eating raw plants such as lettuce and herbs but also by influencing the microbiome of our environment through airflow. This research topic comprising reviews, original and opinion articles highlights the current knowledge regarding plant microbiomes, their specificity, diversity and function as well as all aspects studying the management of plant microbiomes to enhance plant growth, health quality and stress tolerance.

Recent years have seen tremendous progress in unraveling the molecular basis of different plant-microbe interactions. Knowledge has accumulated on the mecha nisms of the microbial infection of plants, which can lead to either disease or resistance. The mechanisms developed by plants to interact with microbes, whether viruses, bacteria, or fungi, involve events that can lead to symbiotic association or to disease or tumor formation. Cell death caused by pathogen infection has been of great interest for many years because of its association with plant resistance. There appear to be two types of plant cell death associated with pathogen infection, a rapid hypersensitive cell death localized at the site of infection during an incompatible interaction between a resistant plant and an avirulent pathogen, and a slow, normosensitive plant cell death that spreads beyond the site of infection during some compatible interactions involving a susceptible plant and a virulent, necrogenic pathogen. Plants possess a number of defense mechanisms against infection, such as (i) production of phytoalexin, (ii) formation of hydrolases, (iii) accumulation of hydroxyproline-rich glycoprotein and lignin deposition, (iv) production of pathogen-related proteins, (v) produc tion of oligosaccharides, jasmonic acid, and various other phenolic substances, and (vi) production of toxin-metabolizing enzymes. Based on these observations, insertion of a single suitable gene in a particular plant has yielded promising results in imparting resistance against specific infection or disease. It appears that a signal received after microbe infection triggers different signal transduction pathways.