12. Root-Microbe Interactions in Response to Soil Conditions

Soil microbes are a substantial component of soils and are essential for many soil functions and capability. Many recent studies have confirmed the beneficial root-microbe associations for soil and plant health, including root growth, fitness, and stress tolerance of plants under different soil conditions. Roots and rhizosphere microbial communities are in flux with the environment; as a result, root-microbe interactions shift in response to soil conditions. Some soil conditions like moisture stress (transient soil condition) and acidity and alkalinity (inherent soil conditions) are common constraints for many beneficial root-microbe interactions. For example, during drought, the plant microbiome is significantly altered in many crops, and plants may select unique microbes to improve drought tolerance. Studies have shown that the phylogenetic and the physiological adaptations by some microbes in response to moisture stress can benefit plants. Soil constraints such as subsoil acidity and aluminum or salt toxicity can be detrimental to some plant-beneficial microbes like mycorrhizae. As a result, novel root-microbe interactions do occur most likely in subsoil, which may be critical for improving root fitness and soil health in the subsoil. There are opportunities to improve the root-microbe interactions through diversification of cropping systems and sustainable management practices. Further research is needed to clearly outline beneficial root-microbe interactions in response to soil conditions and fill knowledge gaps to effectively integrate belowground interactions with soil and crop management.