Editorial The Plant Holobiont Volume II Impacts of the Rhizosphere on Plant Health

Plants live in close association with the microbes that inhabit the rhizosphere, and the presence of this complex plant-associated microbial community is important for plant health. In nature, plants are continuously exposed to a variety of environmental factors that influence both the above- and below-ground structures. In particular, the composition of the root microbiome may be altered by specific biotic and/or abiotic stressors and, subsequently, has consequences on the reconfiguration of the microbiome, which may aid the plant in reacting, and in some cases overcoming, the adverse constraints. Re-modulation of the rhizosphere microbiome composition is often accompanied by active root excretion of selective compounds that can be antagonistic/unfavorable and/or proliferative to microbes. It is of great interest to understand the signaling molecules produced by plants when faced by abiotic and biotic stressors, and to determine how these compounds can be responsible for the recruitment of “helper” microbes in the rhizosphere that aid the plant defense response.

At the same time, the interaction between the plant and its root microbiome can affect plant defense responses and subsequently influence crop productivity and quality. Some root symbiotic microbes may establish positive interactions with plants either by attracting other beneficial microbes or insects, directly or indirectly or by increasing plant tolerance to specific stresses.

This Editorial includes the article collection with the aim to present investigations on plant-microbe interactions occurring in the rhizosphere when plants are subject to biotic or abiotic stress conditions. This will examine the molecular dialogue that occurs not only between the root microbiome and its host plant but also among the components/members of the related microbiota, with special interest on those associations that elicit plant beneficial effects.